New Arid Land Ornamentals

Over the past decade, water conservation has become an increasingly important issue across the southwestern United States. This concern has led local horticulturists and landscape architects to explore the use of water-thrifty ornamentals from dry climates throughout the world. The Chihuahuan and Sonoran deserts in particular have yielded a vast array of successful landscape plants. Universities, growers, and plant enthusiasts have all participated in the collection, propagation, evaluation, and promotion of new plant introductions. A group of recent proven introductions, including trees, shrubs, ground covers, and perennials are included below with information on their origins, growth habits, cultural requirements, and potential uses in the landscape.

Acacia redolens Maslin, Desert Carpet^TM

Native to inland areas of Western Australia, Acacia redolens Maslin has been used extensively in southern California and Arizona to cover large areas inexpensively. Seedlings of Acacia redolens vary widely in their growth habits, often reaching heights in excess of 1.8 m (6 feet). The Desert Carpet™ clone was selected from the first Phoenix freeway plantings for its prostrate growth habit, and was released by Mountain States Wholesale Nursery in 1984. Since that time, this groundcover has performed consistently on many projects, and years after installation has maintained a height of only 0.6 m (24 inches). One plant can spread to a width of 3.6 m (12 feet), although we have observed that the cutting-grown Desert Carpet™ plants are slower to establish and reach their mature size than seedlings. The slower growth rate and prostrate nature of this clone should reduce maintenance costs, since pruning is not necessary to control vertical growth. Instead of true leaves, Acacia redolens has thick, leathery, gray-green phyllodes. This plant blooms in the spring with small yellow flowers. Freeway acacia will tolerate low temperatures of –11.1° to –9.4°C (12°–15°F), alkaline and slightly saline soils, and does not seem to be choosy about soil types. In coastal areas it requires little or no supplemental irrigation, but does require regular irrigation in hot desert regions. Desert Carpet^TM seems to be disease and pest free.

Baccharis hybrid 'Starn' (P.P.A.F.) Thompson^TM

When Dr. Tommy Thompson and Dr. Chi Won Lee of the University of Arizona released Baccharis hybrid 'Centennial', it filled a great void in our plant palette. Their research has been carried on, and now the improved Thompson™ clone is available. Since Baccharis 'Centennial' is a female plant, it has two undesirable characteristics. First, it produces pappus, or white "fluff," which litters the landscape and reduces the esthetic appearance of the plants for a short period of time. Also, since 'Centennial' is a female plant, it can be pollinated by nearby male Baccharis sarothroides Gray (Desert broom), and seedlings often result. This is why you sometimes see stands of 'Centennial' with taller Baccharis plants growing up through them. The Thompson^TM clone is a male plant, eliminating these two negative characteristics. Also, Thompson^TM was selected from the next generation after 'Centennial', and has 25% more Baccharis sarothroides for heat and disease resistance. The growth habits and uses of these two clones are essentially the same: both grow to about 0.9 m (3 feet) tall by 1.2–1.5 m (4-5) feet wide, are evergreen with bright green foliage and inconspicuous flowers, and provide a low-maintenance, long-lived alternative for difficult locations.

Cercidium species 'Desert Museum'

This hybrid palo verde is a three-way cross between Parkinsonia aculeata L., Cercidium microphyllum (Torr.) Rose & I.M. Johnst., and Cercidium floridum Benth. ex Gray, and seems to combine the best qualities of all three plants. 'Desert Museum' grows very rapidly to 6.1 m (20 feet) tall and wide in 3 to 5 years, after which it needs little or no irrigation. It is completely thornless, and produces very little litter, with few seed pods. It has a sturdy, upright growth habit which requires very little pruning or staking. It blooms over a long period of time, with the heaviest bloom from about mid-March to May 1. It also tends to bloom again in June and August. The yellow flowers are larger than any of its three "parents." It does not reseed like the messy Parkinsonia aculeata!

Chilopsis linearis (Cav.) Sweet, Lucretia Hamilton^TM

Desert willow trees occur along washes throughout the southwestern US and northern Mexico. This small deciduous tree has narrow, light green leaves that give it a weeping appearance. In the summer, the tree is covered with fragrant, trumpet-shaped flowers. In the wild, the flower colors range from white to purple, although a pale pink to lavender flower color is the most common. The Lucretia Hamilton^TM clone was selected for its intense, deep pink to purple flower color, as well as its small stature. While many desert willow trees can grow to 7.6 m (25 feet) tall and wide, this clone seems to stay below 5.4–6.1 m (18-20 feet) tall and wide. After flowering, long narrow seed pods are produced. Plant Chilopsis linearis in full sun and well-drained soil, and in regions where temperatures do not drop below –17.8°C (0°F).

Chrysactinia mexicana Gray (Damianita)

This small, compact shrub grows to 0.6 m (2 feet) tall and wide, and bears a very strong resemblance to turpentine bush, with needle-like green leaves and yellow daisy-like flowers. However, damianita blooms from March to September, while turpentine bush blooms from September to November. Combining the two plants would be a great way to prolong the color display! Damianita has wonderful-smelling foliage, and would be a great selection for sensory gardens. Damianita is a very tough, durable plant, tolerating extreme heat and cold, down to –17.8°C (0°F). Plant in full sun, and almost any soil. If this plant starts to look woody, prune it back severely in the early spring. Damianita ranges from New Mexico to west Texas and northeastern Mexico, at elevations of 609–2134 m (2000–7000 feet).

Dalea capitata Sierra Gold^TM

This well-behaved ground cover grows to about 20 cm (8 inches) tall by 0.9 m (3 feet) wide. Because of its compact size, Sierra Gold^TM is a good selection for tight planting areas, such as small planters or medians. Its fine-textured, light green foliage has a fresh, lemony scent. Rabbits seem to avoid it! Yellow flowers carpet Sierra Gold^TM in the spring and the fall. This plant is hardy to at least –15°C (5°F), but it will be deciduous at –3.9°C (25°F). The one drawback to this plant is that the whiteflies seem to like it, so some insecticide applications will be necessary in heavily infested areas around Phoenix. Plant in full sun for best results. No soil amendments should be necessary. In hot desert regions this plant requires some supplemental irrigation from spring to fall. Although most dales native to Arizona and Mexico tend to rot out if overwatered, we have observed this plant thriving right next to turfgrass, where it receives heavy irrigation. More testing is needed to determine if it will tolerate coastal areas, or regions with high rainfall.

Dasylirion longissimum

This user-friendly accent plant is a great selection for high-traffic areas such as walkways and near entries. This grasslike plant does well in containers, and its symmetrical form provides a striking focal point. Its thin, stiff green leaves are completely unarmed, and have smooth edges. Eventually, its single trunk can grow to 1.8 m (6 feet), topped by a 1.5 m- (5-foot-) wide rounded head of leaves. The older, bottom leaves can be trimmed off to expose the trunk. Dasylirion longissimum is native to Mexico, and is hardy to about –8.3°C (17°F).

Euphorbia biglandulosa Desf. (Gopher Plant)

This evergreen perennial or subshrub has a very unusual form and appearance. Its arching stems angle out and up, and can reach a length of 0.6 m (2 feet). The plant grows to 0.9 m (3 feet) tall by 1.2 m (4 feet) across; with narrow, fleshy grey-green leaves. Broad clusters of chartreuse flowers occur at the tips of the arching stems, usually in the late winter and early spring. Flowers are followed by small brown seed pods that explode upon ripening. The stems usually die back after fruiting, leaving a small clump of grey-green foliage near the ground. Plant Euphorbia biglandulosa in full sun or light shade, in a well-draining soil. It is cold hardy to –15°C (5°F).

Hesperaloe parviflora (Torr.) J. Coult., 'Yellow' (Yellow yucca)

A clumping perennial with long, gray-green leaves, Hesperaloe parviflora grows slowly to form a grasslike clump 1.0–1.2 m (3–4 feet) tall and wide. From spring through fall, it produces 1.5 m- (5-foot-) tall flower spikes. Red-flowering plants have been a staple in southwestern landscapes for many years. This is simply a yellow-flowering selection. Use this tough accent plant in full sun. Since it also tolerates reflected heat, yellow yucca is a reliable plant to use along sidewalks, in parking lots, etc. Tolerant of temperature extremes, yellow yucca is cold-hardy to at least –17.8°C (0°F). Once established, it requires little or no irrigation. All in all, yellow yucca is one of the toughest and most maintenance-free plants.

Hymenoxys acaulis (Pursh) K. Parker (Angelita Daisy)

This perennial is native to the southwestern US, where it occurs most often at elevations from 1219–2134 m (4000–7000 feet), on dry rocky slopes and mesas. Angelita daisy bears a strong resemblance to Baileya multiradiata Harv. & A. Gray ex Torr. (desert marigold). However, the foliage is green rather than gray, and the flower is a deeper gold color. Forming rounded clumps to fifteen inches tall and wide, Hymenoxys acaulis is a wonderful plant to use as a border in front of larger shrubs. I f water is available, it will naturalize in the landscape. In Phoenix, this plant blooms all year, with especially heavy bloom in the spring and fall months. This prolonged bloom period results in many dried flower stalks, which can make the plants look scruffy. We recommend cutting off the old flower spikes occasionally to rejuvenate the plant and initiate new flower production. Angelita daisy seems to prefer well-drained soils and full sun. It is very cold hardy, heat tolerant, and drought tolerant.

Leucophyllum candidum I.M. Johnst. Thunder Cloud^TM

As with all of the other Leucophyllum species, this clone blooms when the humidity is high. The silver, pubescent foliage is a perfect foil for the masses of indigo flowers that appear in the summer and fall months. Thunder Cloud^TM was selected and trademarked by Benny Simpson of Texas A&M University. His clone is highly valued because of its small, dense growth habit. Unlike most of the larger Leucophyllum species, Thunder Cloud^TM remains reliably small, to three feet tall and wide. This plant is cold hardy to at least –12.2°C (10°F). Plant all of the Leucophyllum species in full sun and well-drained soil. Avoid overwatering.

Leucophyllum langmaniae Rio Bravo^TM

Trademarked by Mountain States Nursery, this clone has a nice, compact growth habit very similar to L. frutescens 'Compacta'. Rio Bravo^TM has become very popular because of its bright green foliage and rounded, dense form. It has lavender flowers and will eventually grow to 1.5 m (5 feet) tall and wide. Like the L. candidum species, it requires well-drained soils and full sun. It is hardy to –12.2°C (10°F).

Muhlenbergia capillaris (Lam.) Trin. Regal Mist^TM

We feel that this ornamental grass shows great promise for many different regions of the country. Native to humid southeastern Texas, this grass has adapted extremely well to the hot, dry conditions of deserts in Arizona and Nevada. In fact, it has performed incredibly well in Las Vegas, which is cursed with poor soils, high winds, high summer temperatures, and cold winters. Regal Mist^TM is also happy in heavy soils, with ample irrigation. In short, it has worked everywhere it has been tried, so far! It is hardy to at least –17.8°C (0°F). Regal Mist^TM has narrow, dark green, glossy leaves. It grows quickly to form a rounded clump to 0.9 m (3 feet) tall and wide. The flower spikes on this grass have attracted a lot of attention... they form misty masses of pink to purple flowers in October and November. We recommend cutting this plant back in early spring to cut off the dead flower spikes and any dormant foliage.

Penstemon species

There are so many wonderful Penstemon species to try in the garden, that is difficult to select just a few. Most of the penstemons are perennials with a basal rosette of foliage, which send up spikes of tubular flowers in the spring and early summer. They add incredible color to the landscape, and attract hummingbirds as well! Penstemons come in a wide range of colors, including blue, purple, pink, and red. After they finish blooming, allow the flower spikes to dry on the plant. Then cut off the spikes and sprinkle the seed in the garden to increase next year's mass of color. There are two new species to try: Penstemon triflorus Heller, which has short, 46 cm (18 inch) spikes of dark pink-purple flowers which occur along the stem in clusters of three; and Penstemon clevelandii Gray, native to southern and Baja California, with spikes of clear, bright pink flowers to 0.6–0.8 m (2–2.5 feet) tall.

New Arid Land Ornamentals

Over the past decade, water conservation has become an increasingly important issue across the southwestern United States. This concern has led local horticulturists and landscape architects to explore the use of water-thrifty ornamentals from dry climates throughout the world. The Chihuahuan and Sonoran deserts in particular have yielded a vast array of successful landscape plants. Universities, growers, and plant enthusiasts have all participated in the collection, propagation, evaluation, and promotion of new plant introductions. A group of recent proven introductions, including trees, shrubs, ground covers, and perennials are included below with information on their origins, growth habits, cultural requirements, and potential uses in the landscape.

Acacia redolens Maslin, Desert Carpet^TM

Native to inland areas of Western Australia, Acacia redolens Maslin has been used extensively in southern California and Arizona to cover large areas inexpensively. Seedlings of Acacia redolens vary widely in their growth habits, often reaching heights in excess of 1.8 m (6 feet). The Desert Carpet™ clone was selected from the first Phoenix freeway plantings for its prostrate growth habit, and was released by Mountain States Wholesale Nursery in 1984. Since that time, this groundcover has performed consistently on many projects, and years after installation has maintained a height of only 0.6 m (24 inches). One plant can spread to a width of 3.6 m (12 feet), although we have observed that the cutting-grown Desert Carpet™ plants are slower to establish and reach their mature size than seedlings. The slower growth rate and prostrate nature of this clone should reduce maintenance costs, since pruning is not necessary to control vertical growth. Instead of true leaves, Acacia redolens has thick, leathery, gray-green phyllodes. This plant blooms in the spring with small yellow flowers. Freeway acacia will tolerate low temperatures of –11.1° to –9.4°C (12°–15°F), alkaline and slightly saline soils, and does not seem to be choosy about soil types. In coastal areas it requires little or no supplemental irrigation, but does require regular irrigation in hot desert regions. Desert Carpet^TM seems to be disease and pest free.

Baccharis hybrid 'Starn' (P.P.A.F.) Thompson^TM

When Dr. Tommy Thompson and Dr. Chi Won Lee of the University of Arizona released Baccharis hybrid 'Centennial', it filled a great void in our plant palette. Their research has been carried on, and now the improved Thompson™ clone is available. Since Baccharis 'Centennial' is a female plant, it has two undesirable characteristics. First, it produces pappus, or white "fluff," which litters the landscape and reduces the esthetic appearance of the plants for a short period of time. Also, since 'Centennial' is a female plant, it can be pollinated by nearby male Baccharis sarothroides Gray (Desert broom), and seedlings often result. This is why you sometimes see stands of 'Centennial' with taller Baccharis plants growing up through them. The Thompson^TM clone is a male plant, eliminating these two negative characteristics. Also, Thompson^TM was selected from the next generation after 'Centennial', and has 25% more Baccharis sarothroides for heat and disease resistance. The growth habits and uses of these two clones are essentially the same: both grow to about 0.9 m (3 feet) tall by 1.2–1.5 m (4-5) feet wide, are evergreen with bright green foliage and inconspicuous flowers, and provide a low-maintenance, long-lived alternative for difficult locations.

Cercidium species 'Desert Museum'

This hybrid palo verde is a three-way cross between Parkinsonia aculeata L., Cercidium microphyllum (Torr.) Rose & I.M. Johnst., and Cercidium floridum Benth. ex Gray, and seems to combine the best qualities of all three plants. 'Desert Museum' grows very rapidly to 6.1 m (20 feet) tall and wide in 3 to 5 years, after which it needs little or no irrigation. It is completely thornless, and produces very little litter, with few seed pods. It has a sturdy, upright growth habit which requires very little pruning or staking. It blooms over a long period of time, with the heaviest bloom from about mid-March to May 1. It also tends to bloom again in June and August. The yellow flowers are larger than any of its three "parents." It does not reseed like the messy Parkinsonia aculeata!

Chilopsis linearis (Cav.) Sweet, Lucretia Hamilton^TM

Desert willow trees occur along washes throughout the southwestern US and northern Mexico. This small deciduous tree has narrow, light green leaves that give it a weeping appearance. In the summer, the tree is covered with fragrant, trumpet-shaped flowers. In the wild, the flower colors range from white to purple, although a pale pink to lavender flower color is the most common. The Lucretia Hamilton^TM clone was selected for its intense, deep pink to purple flower color, as well as its small stature. While many desert willow trees can grow to 7.6 m (25 feet) tall and wide, this clone seems to stay below 5.4–6.1 m (18-20 feet) tall and wide. After flowering, long narrow seed pods are produced. Plant Chilopsis linearis in full sun and well-drained soil, and in regions where temperatures do not drop below –17.8°C (0°F).

Chrysactinia mexicana Gray (Damianita)

This small, compact shrub grows to 0.6 m (2 feet) tall and wide, and bears a very strong resemblance to turpentine bush, with needle-like green leaves and yellow daisy-like flowers. However, damianita blooms from March to September, while turpentine bush blooms from September to November. Combining the two plants would be a great way to prolong the color display! Damianita has wonderful-smelling foliage, and would be a great selection for sensory gardens. Damianita is a very tough, durable plant, tolerating extreme heat and cold, down to –17.8°C (0°F). Plant in full sun, and almost any soil. If this plant starts to look woody, prune it back severely in the early spring. Damianita ranges from New Mexico to west Texas and northeastern Mexico, at elevations of 609–2134 m (2000–7000 feet).

Dalea capitata Sierra Gold^TM

This well-behaved ground cover grows to about 20 cm (8 inches) tall by 0.9 m (3 feet) wide. Because of its compact size, Sierra Gold^TM is a good selection for tight planting areas, such as small planters or medians. Its fine-textured, light green foliage has a fresh, lemony scent. Rabbits seem to avoid it! Yellow flowers carpet Sierra Gold^TM in the spring and the fall. This plant is hardy to at least –15°C (5°F), but it will be deciduous at –3.9°C (25°F). The one drawback to this plant is that the whiteflies seem to like it, so some insecticide applications will be necessary in heavily infested areas around Phoenix. Plant in full sun for best results. No soil amendments should be necessary. In hot desert regions this plant requires some supplemental irrigation from spring to fall. Although most dales native to Arizona and Mexico tend to rot out if overwatered, we have observed this plant thriving right next to turfgrass, where it receives heavy irrigation. More testing is needed to determine if it will tolerate coastal areas, or regions with high rainfall.

Dasylirion longissimum

This user-friendly accent plant is a great selection for high-traffic areas such as walkways and near entries. This grasslike plant does well in containers, and its symmetrical form provides a striking focal point. Its thin, stiff green leaves are completely unarmed, and have smooth edges. Eventually, its single trunk can grow to 1.8 m (6 feet), topped by a 1.5 m- (5-foot-) wide rounded head of leaves. The older, bottom leaves can be trimmed off to expose the trunk. Dasylirion longissimum is native to Mexico, and is hardy to about –8.3°C (17°F).

Euphorbia biglandulosa Desf. (Gopher Plant)

This evergreen perennial or subshrub has a very unusual form and appearance. Its arching stems angle out and up, and can reach a length of 0.6 m (2 feet). The plant grows to 0.9 m (3 feet) tall by 1.2 m (4 feet) across; with narrow, fleshy grey-green leaves. Broad clusters of chartreuse flowers occur at the tips of the arching stems, usually in the late winter and early spring. Flowers are followed by small brown seed pods that explode upon ripening. The stems usually die back after fruiting, leaving a small clump of grey-green foliage near the ground. Plant Euphorbia biglandulosa in full sun or light shade, in a well-draining soil. It is cold hardy to –15°C (5°F).

Hesperaloe parviflora (Torr.) J. Coult., 'Yellow' (Yellow yucca)

A clumping perennial with long, gray-green leaves, Hesperaloe parviflora grows slowly to form a grasslike clump 1.0–1.2 m (3–4 feet) tall and wide. From spring through fall, it produces 1.5 m- (5-foot-) tall flower spikes. Red-flowering plants have been a staple in southwestern landscapes for many years. This is simply a yellow-flowering selection. Use this tough accent plant in full sun. Since it also tolerates reflected heat, yellow yucca is a reliable plant to use along sidewalks, in parking lots, etc. Tolerant of temperature extremes, yellow yucca is cold-hardy to at least –17.8°C (0°F). Once established, it requires little or no irrigation. All in all, yellow yucca is one of the toughest and most maintenance-free plants.

Hymenoxys acaulis (Pursh) K. Parker (Angelita Daisy)

This perennial is native to the southwestern US, where it occurs most often at elevations from 1219–2134 m (4000–7000 feet), on dry rocky slopes and mesas. Angelita daisy bears a strong resemblance to Baileya multiradiata Harv. & A. Gray ex Torr. (desert marigold). However, the foliage is green rather than gray, and the flower is a deeper gold color. Forming rounded clumps to fifteen inches tall and wide, Hymenoxys acaulis is a wonderful plant to use as a border in front of larger shrubs. I f water is available, it will naturalize in the landscape. In Phoenix, this plant blooms all year, with especially heavy bloom in the spring and fall months. This prolonged bloom period results in many dried flower stalks, which can make the plants look scruffy. We recommend cutting off the old flower spikes occasionally to rejuvenate the plant and initiate new flower production. Angelita daisy seems to prefer well-drained soils and full sun. It is very cold hardy, heat tolerant, and drought tolerant.

Leucophyllum candidum I.M. Johnst. Thunder Cloud^TM

As with all of the other Leucophyllum species, this clone blooms when the humidity is high. The silver, pubescent foliage is a perfect foil for the masses of indigo flowers that appear in the summer and fall months. Thunder Cloud^TM was selected and trademarked by Benny Simpson of Texas A&M University. His clone is highly valued because of its small, dense growth habit. Unlike most of the larger Leucophyllum species, Thunder Cloud^TM remains reliably small, to three feet tall and wide. This plant is cold hardy to at least –12.2°C (10°F). Plant all of the Leucophyllum species in full sun and well-drained soil. Avoid overwatering.

Leucophyllum langmaniae Rio Bravo^TM

Trademarked by Mountain States Nursery, this clone has a nice, compact growth habit very similar to L. frutescens 'Compacta'. Rio Bravo^TM has become very popular because of its bright green foliage and rounded, dense form. It has lavender flowers and will eventually grow to 1.5 m (5 feet) tall and wide. Like the L. candidum species, it requires well-drained soils and full sun. It is hardy to –12.2°C (10°F).

Muhlenbergia capillaris (Lam.) Trin. Regal Mist^TM

We feel that this ornamental grass shows great promise for many different regions of the country. Native to humid southeastern Texas, this grass has adapted extremely well to the hot, dry conditions of deserts in Arizona and Nevada. In fact, it has performed incredibly well in Las Vegas, which is cursed with poor soils, high winds, high summer temperatures, and cold winters. Regal Mist^TM is also happy in heavy soils, with ample irrigation. In short, it has worked everywhere it has been tried, so far! It is hardy to at least –17.8°C (0°F). Regal Mist^TM has narrow, dark green, glossy leaves. It grows quickly to form a rounded clump to 0.9 m (3 feet) tall and wide. The flower spikes on this grass have attracted a lot of attention... they form misty masses of pink to purple flowers in October and November. We recommend cutting this plant back in early spring to cut off the dead flower spikes and any dormant foliage.

Penstemon species

There are so many wonderful Penstemon species to try in the garden, that is difficult to select just a few. Most of the penstemons are perennials with a basal rosette of foliage, which send up spikes of tubular flowers in the spring and early summer. They add incredible color to the landscape, and attract hummingbirds as well! Penstemons come in a wide range of colors, including blue, purple, pink, and red. After they finish blooming, allow the flower spikes to dry on the plant. Then cut off the spikes and sprinkle the seed in the garden to increase next year's mass of color. There are two new species to try: Penstemon triflorus Heller, which has short, 46 cm (18 inch) spikes of dark pink-purple flowers which occur along the stem in clusters of three; and Penstemon clevelandii Gray, native to southern and Baja California, with spikes of clear, bright pink flowers to 0.6–0.8 m (2–2.5 feet) tall.

Acacia nilotica (L.) Del

Uses

Some feel that the thorn bush of Exodus 3 was Acacia nilotica, the fire, the parasite Loranthus acaciae. Inner bark contains 18–23% tannin, used for tanning and dyeing leather black. Young pods produce a very pale tint in leather, notably goat hides (Kano leather). Pods were used by the ancient Egyptians. Young bark used as fiber, twigs esteemed for tooth brushes (chewsticks). Trees tapped for gum arabic. The gum arabic is still used in making candles, inks, matches, and paints (NAS, 1980). Tender pods and shoots used as vegetable, and used as forage for camels, sheep and goats, especially in Sudan, where it is said to improve milk from these animals. Seeds are a valuable cattle food. Roasted seed kernels, sometimes used for flavoring and when crushed provide the dye for black strings worn by Nankani women. Trees used in Sudan for afforestation of inundated areas. Sapwood is yellowish-white, heartwood reddish-brown, hard, heavy, durable, difficult to work, though taking a high polish. Because of its resins, it resists insects and water, and trees are harvested for the timber for boat-making, posts, buildings, water-pipes, well-planking, plows, cabinet-work, wheels, mallets and other implements. Wood yields excellent firewood and charcoal (Duke, 1981a). The aqueous extract of the fruit, rich in tannin (18–23%) has shown algicidal activity against Chroccoccus, Closteruim, Coelastrum, Cosmarium, Cyclotella, Euglena, Microcystis, Oscillatoria, Pediastrum, Rivularia, Spirogyra, and Spirulina (Ayoub, 1983).

Folk Medicine

Zulu take bark for cough, Chipi use root for tuberculosis. Masai are intoxicated by the bark and root decoction, said to impart courage, even aphrodisia, and the root is said to cure impotence. Astringent bark used for diarrhea, dysentery, and leprosy. Bruised leaves poulticed onto ulcers. According to Hartwell, the gum or bark is used for cancers and/or tumors (of ear, eye, or testicles) and indurations of liver and spleen, condylomas, and excess flesh. Said also to be used for cancer, colds, congestion, coughs, diarrhea, dysentery, fever, gallbladder, hemorrhage, hemorrhoids, leucorrhea, ophthalmia, sclerosis, smallpox, and tuberculosis. Bark, gum, leaves, and pods used medicinally in West Africa. Sap or bark, leaves, and young pods are strongly astringent due to tannin, and are chewed In Senegal as antiscorbutic; in Ethiopia as lactogogue. Bark decoction drunk for intestinal pains and diarrhea. Other preparations used for coughs, gargle, toothache, ophthalmia, and syphilitic ulcers. In Tonga, the root is used to treat tuberculosis. In Lebanon, the resin is mixed with orange-flower infusion for typhoid convalescence. Masai use the bark decoction as a nerve stimulant. In Italian Africa, the wood is used to treat smallpox. Egyptian Nubians believe that diabetics may eat unlimited carbohydrates as long as they also consume powdered pods (Duke, 1983a). Extracts are inhibitory to at least four species of pathogenic fungi (Umalkar et al, 1976).

Chemistry

Babul has been reported to contain l-arabinose, catechol, galactan, galactoaraban, galactose, N-acetyldjenkolic acid, N-acetyldjenkolic acid, sulphoxides pentosan, saponin, tannin. Seeds contain crude protein 18.6%, ether extract 4.4%, fiber 10.1%, nitrogen-free extract 61.2%, ash 5.7%, and silica 0.44%. Phosphorus 0.29% and calcium 0.90% of DM. When bullocks were given the seeds and bran (2:1) with dry pasture grass daily DM intakes were 1.82, 0.91, and 5.35 kg respectively. Total DM intake/100 kg bodyweight was 1.40 kg. The animals retained 20.8 g N and 7.4 g Ca daily but the P balance was slightly negative (Pande et al, 1981). Walker (1980) puts the CP content of the browse at 12.9%, the crude fiber at 15.2%

Description

Small tree, 2.5–14 m tall, quite variable in many aspects; bark of twigs not flaking off, gray to brown; branches spreading, with flat or rounded crown; bark thin, rough, fissured, deep red-brown; branchlets purple-brown, shortly or densely gray-pubescent, with lenticels; spines gray-pubescent, slightly recurved, up to 3 cm long; leaves often with 1–2 petiolar glands and other glands between all or only the uppermost pinnae; plnnae 2–11 (-17) pairs; leaflets 7–25 (-30) pairs, 1.5–7 mm long, 0.5–1.5 mm wide, glabrous or pubescent, apex obtuse; peduncles clustered at nodes of leafy and leafless branchlets; flowers bright yellow, in axillary heads 6–15 mm in diam.; involucel from near the base to about half-way up the peduncle, rarely somewhat higher; calyx 1–2 mm long, subglabrous to pubescent; corolla 2.5–3.5 mm long, glabrous or pubescent outside; pods especially variable, linear, indehiscent, 8–17 (-24) cm long, 1.3–2.2 cm broad, straight or curved, glabrous or gray-velvety, turgid, blackish, about 12-seeded; seeds deep blackish-brown, smooth, subcircular, compressed, areole 6–7 mm long, 4.5–5 mm wide. Fl. Oct.–Dec.; fr. Mar.–June (Duke, 1981a).

Germplasm

Acacia nilotica var. kraussiana (Benth.) Brenan is the most common form in east tropical Africa. Young branches more or less densely pubescent; pods not necklace-like, 1–1.8 cm wide, oblong, more or less pubescent all over at first with raised parts over seeds becoming glabrescent, shining and black when dry, margins shallowly crenate. Exhibits wide range of altitudinal and habitat requirements. Found in Botswana, Zambia, Rhodesia, Malawi, Tanzania, Angola, Mozambique, Transvaal, and Natal. A. nilotica var. tomentosa A. F. Hill (A. arabica var. tomentosa Benth.), has pods straight, constricted between seeds and densely tomentose; found in Senegal and northern Nigeria, to Sudan, Arabia and India. A. nilotica var. adansonii (Guill. et Perr.) Kuntze is a tree up to 17 m with dark reddish-brown bark deeply fissured, tomentose, reddish-brown twigs and gray fruits; commonest variety in West Africa, from Senegal to Nigeria and widespread in northern parts of Tropical Africa. Assigned to the African Center of Diversity, babul or cvs thereof is reported to exhibit tolerance to clay, drought, heat, heavy soil, high pH, poor soils, salt, savanna, and waterlogging. (2n=52.)

Distribution

Native from Egypt south to Mozambique and Natal; apparently introduced to Zanzibar, Pemba, and India; Arabia. Considered a serious weed in South Africa.

Ecology

Woodlands of various sorts, wooded grasslands, scrub and thickets. Thrives in dry areas, but endures floods. Grows 10–1,340 m altitude, in a wide range of conditions. Grows on a wide variety of soils, seemingly thriving on alluvial soils, black cotton soils, heavy clay soils, as well as even poorer soils (NAS, 1980). Ranging from Subtropical Desert to Subtropical Dry through Tropical Desert to Tropical Dry Forest Life Zones, babul is reported to tolerate annual precipitation of 3.8–22.8 dm (mean of 12 cases = 12.0 dm), annual mean temperature of 18.7–27.8°C (mean of 12 cases = 24.1°C), and pH of 5.0–8.0 (mean of 10 cases = 6.9) (Duke, 1981a).

Cultivation

Trees propagated in forest by seeds. Direct seeding is the common practice. Stored seed may require scarification. Young seedlings are said to "require full sun and frequent weeding" (NAS, 1980a).

Harvesting

Although there are other sources of gum arabic, trees are still tapped for the gum by removing a bit of bark 5–7.5 cm wide and bruising the surrounding bark with mallet or hammer. The resulting reddish gum, almost completely soluble and tasteless, is formed into balls. Though used in commerce to some extent, it is inferior to other forms of gum arabic, with which it is sometimes mixed.

Yields and Economics

Various products of the tree are used locally in tropical Africa, but none enter international markets. Trees usually add 2–3 cm in diameter each year (NAS, 1980a).

Energy

Extensively used, e.g. in India, for firewood and charcoal, this species has been used in locomotives and steamships as well as industry balers. It is cultivated for industrial fuel in the Sudan. The calorific value of the sapwood is 4,800 kcal/kg of the heartwood 4,950. The species does nodulate and fix nitrogen.

Biotic Factors

Wood borers may afflict the stems and bruchids may afflict the seeds. Following fungi have been reported on this plant: Ctyospora acaciae, Diatryphe acaciae, Diplodia acaciae, Fomes badius, F. endotheius, F. fastuosus, F. rimosus, Fusicoccum indicum, Phyllactinia acaciae, Ravenelia acaciae-arabicae, Septogloeum acaciae, Septoria mortolensis, Sphaerostilbe acaciae. Trees are also parasitized by Dendrophthoe falcata and Loranthus globiferus var. verrucosus (Duke, 1981). In a survey for phytophagous insects on Acacia nilotica, 43 species were recorded in Pakistan, of these, 16 appeared stenophagous. The more promising for biological control of the tree were: Anarsia sp. cf. acaciae, Pseudosterrha paulula, Azanus ubaldus, and Ceutholopha isidis feeding on flowers; Bruchidius sahlbergi and Sulcobruchus sp. damaging seeds; Ascalenia callynella, Gisilia stereodoxa and an unidentified gracillariid boring shoots; and Cydia sp. making stem galls (Mohyuddin, 1981).

Yields and Economics

Various products of the tree are used locally in tropical Africa, blit none enter international markets. Trees usually add 2–3 cm in diameter each year (NAS, 1980).

References

• Ayoub, S.M.H. 1983. Algicidal properties of Acacia nilotica. Fitoterapia 53(5–6):175–8.
  
• Duke, 1981.
  
• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Duke, J.A. 1983a. Medicinal plants of the Bible. Trado-Medic Books, Owerri, NY.
  
• Mohyuddin, A.I. 1981. Phytophages associated with Acacia nilotica in Pakistan and possibilities of their introduction into Australia. p. 161–166. Proceedings of the 5th International Symposium on Biological Control of Weeds. Australia Commonwealth Scientific and Industrial Research Organization.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Pande, M.B., Talpada, P.M., Patel, J.S., and Shukla, P.C. 1981. Note on the nutritive value of babul (Acacia nilotica L.) seeds (extracted). In: Indian J. Anim. Sci. 51(1):107–108.
  
• Umalkar, C.V., Begum, S., Nehemiah, K.M.A. 1976. Inhibitory effect of Acacia nilotica extracts on pectolytic enzyme production by some pathogenic fungi. Indian Phytopath.: publ. 1977, 29(4):469–470.
  
• Walker, B.H. 1980. A review of browse and its role in livestock production in southern Africa. p. 7–24. In: LeHouerou, H.N. (ed.), Browse in Africa. International Livestock Centre for Africa. Addis Ababa, Ethiopia.

Acacia nilotica (L.) Del

Uses

Some feel that the thorn bush of Exodus 3 was Acacia nilotica, the fire, the parasite Loranthus acaciae. Inner bark contains 18–23% tannin, used for tanning and dyeing leather black. Young pods produce a very pale tint in leather, notably goat hides (Kano leather). Pods were used by the ancient Egyptians. Young bark used as fiber, twigs esteemed for tooth brushes (chewsticks). Trees tapped for gum arabic. The gum arabic is still used in making candles, inks, matches, and paints (NAS, 1980). Tender pods and shoots used as vegetable, and used as forage for camels, sheep and goats, especially in Sudan, where it is said to improve milk from these animals. Seeds are a valuable cattle food. Roasted seed kernels, sometimes used for flavoring and when crushed provide the dye for black strings worn by Nankani women. Trees used in Sudan for afforestation of inundated areas. Sapwood is yellowish-white, heartwood reddish-brown, hard, heavy, durable, difficult to work, though taking a high polish. Because of its resins, it resists insects and water, and trees are harvested for the timber for boat-making, posts, buildings, water-pipes, well-planking, plows, cabinet-work, wheels, mallets and other implements. Wood yields excellent firewood and charcoal (Duke, 1981a). The aqueous extract of the fruit, rich in tannin (18–23%) has shown algicidal activity against Chroccoccus, Closteruim, Coelastrum, Cosmarium, Cyclotella, Euglena, Microcystis, Oscillatoria, Pediastrum, Rivularia, Spirogyra, and Spirulina (Ayoub, 1983).

Folk Medicine

Zulu take bark for cough, Chipi use root for tuberculosis. Masai are intoxicated by the bark and root decoction, said to impart courage, even aphrodisia, and the root is said to cure impotence. Astringent bark used for diarrhea, dysentery, and leprosy. Bruised leaves poulticed onto ulcers. According to Hartwell, the gum or bark is used for cancers and/or tumors (of ear, eye, or testicles) and indurations of liver and spleen, condylomas, and excess flesh. Said also to be used for cancer, colds, congestion, coughs, diarrhea, dysentery, fever, gallbladder, hemorrhage, hemorrhoids, leucorrhea, ophthalmia, sclerosis, smallpox, and tuberculosis. Bark, gum, leaves, and pods used medicinally in West Africa. Sap or bark, leaves, and young pods are strongly astringent due to tannin, and are chewed In Senegal as antiscorbutic; in Ethiopia as lactogogue. Bark decoction drunk for intestinal pains and diarrhea. Other preparations used for coughs, gargle, toothache, ophthalmia, and syphilitic ulcers. In Tonga, the root is used to treat tuberculosis. In Lebanon, the resin is mixed with orange-flower infusion for typhoid convalescence. Masai use the bark decoction as a nerve stimulant. In Italian Africa, the wood is used to treat smallpox. Egyptian Nubians believe that diabetics may eat unlimited carbohydrates as long as they also consume powdered pods (Duke, 1983a). Extracts are inhibitory to at least four species of pathogenic fungi (Umalkar et al, 1976).

Chemistry

Babul has been reported to contain l-arabinose, catechol, galactan, galactoaraban, galactose, N-acetyldjenkolic acid, N-acetyldjenkolic acid, sulphoxides pentosan, saponin, tannin. Seeds contain crude protein 18.6%, ether extract 4.4%, fiber 10.1%, nitrogen-free extract 61.2%, ash 5.7%, and silica 0.44%. Phosphorus 0.29% and calcium 0.90% of DM. When bullocks were given the seeds and bran (2:1) with dry pasture grass daily DM intakes were 1.82, 0.91, and 5.35 kg respectively. Total DM intake/100 kg bodyweight was 1.40 kg. The animals retained 20.8 g N and 7.4 g Ca daily but the P balance was slightly negative (Pande et al, 1981). Walker (1980) puts the CP content of the browse at 12.9%, the crude fiber at 15.2%

Description

Small tree, 2.5–14 m tall, quite variable in many aspects; bark of twigs not flaking off, gray to brown; branches spreading, with flat or rounded crown; bark thin, rough, fissured, deep red-brown; branchlets purple-brown, shortly or densely gray-pubescent, with lenticels; spines gray-pubescent, slightly recurved, up to 3 cm long; leaves often with 1–2 petiolar glands and other glands between all or only the uppermost pinnae; plnnae 2–11 (-17) pairs; leaflets 7–25 (-30) pairs, 1.5–7 mm long, 0.5–1.5 mm wide, glabrous or pubescent, apex obtuse; peduncles clustered at nodes of leafy and leafless branchlets; flowers bright yellow, in axillary heads 6–15 mm in diam.; involucel from near the base to about half-way up the peduncle, rarely somewhat higher; calyx 1–2 mm long, subglabrous to pubescent; corolla 2.5–3.5 mm long, glabrous or pubescent outside; pods especially variable, linear, indehiscent, 8–17 (-24) cm long, 1.3–2.2 cm broad, straight or curved, glabrous or gray-velvety, turgid, blackish, about 12-seeded; seeds deep blackish-brown, smooth, subcircular, compressed, areole 6–7 mm long, 4.5–5 mm wide. Fl. Oct.–Dec.; fr. Mar.–June (Duke, 1981a).

Germplasm

Acacia nilotica var. kraussiana (Benth.) Brenan is the most common form in east tropical Africa. Young branches more or less densely pubescent; pods not necklace-like, 1–1.8 cm wide, oblong, more or less pubescent all over at first with raised parts over seeds becoming glabrescent, shining and black when dry, margins shallowly crenate. Exhibits wide range of altitudinal and habitat requirements. Found in Botswana, Zambia, Rhodesia, Malawi, Tanzania, Angola, Mozambique, Transvaal, and Natal. A. nilotica var. tomentosa A. F. Hill (A. arabica var. tomentosa Benth.), has pods straight, constricted between seeds and densely tomentose; found in Senegal and northern Nigeria, to Sudan, Arabia and India. A. nilotica var. adansonii (Guill. et Perr.) Kuntze is a tree up to 17 m with dark reddish-brown bark deeply fissured, tomentose, reddish-brown twigs and gray fruits; commonest variety in West Africa, from Senegal to Nigeria and widespread in northern parts of Tropical Africa. Assigned to the African Center of Diversity, babul or cvs thereof is reported to exhibit tolerance to clay, drought, heat, heavy soil, high pH, poor soils, salt, savanna, and waterlogging. (2n=52.)

Distribution

Native from Egypt south to Mozambique and Natal; apparently introduced to Zanzibar, Pemba, and India; Arabia. Considered a serious weed in South Africa.

Ecology

Woodlands of various sorts, wooded grasslands, scrub and thickets. Thrives in dry areas, but endures floods. Grows 10–1,340 m altitude, in a wide range of conditions. Grows on a wide variety of soils, seemingly thriving on alluvial soils, black cotton soils, heavy clay soils, as well as even poorer soils (NAS, 1980). Ranging from Subtropical Desert to Subtropical Dry through Tropical Desert to Tropical Dry Forest Life Zones, babul is reported to tolerate annual precipitation of 3.8–22.8 dm (mean of 12 cases = 12.0 dm), annual mean temperature of 18.7–27.8°C (mean of 12 cases = 24.1°C), and pH of 5.0–8.0 (mean of 10 cases = 6.9) (Duke, 1981a).

Cultivation

Trees propagated in forest by seeds. Direct seeding is the common practice. Stored seed may require scarification. Young seedlings are said to "require full sun and frequent weeding" (NAS, 1980a).

Harvesting

Although there are other sources of gum arabic, trees are still tapped for the gum by removing a bit of bark 5–7.5 cm wide and bruising the surrounding bark with mallet or hammer. The resulting reddish gum, almost completely soluble and tasteless, is formed into balls. Though used in commerce to some extent, it is inferior to other forms of gum arabic, with which it is sometimes mixed.

Yields and Economics

Various products of the tree are used locally in tropical Africa, but none enter international markets. Trees usually add 2–3 cm in diameter each year (NAS, 1980a).

Energy

Extensively used, e.g. in India, for firewood and charcoal, this species has been used in locomotives and steamships as well as industry balers. It is cultivated for industrial fuel in the Sudan. The calorific value of the sapwood is 4,800 kcal/kg of the heartwood 4,950. The species does nodulate and fix nitrogen.

Biotic Factors

Wood borers may afflict the stems and bruchids may afflict the seeds. Following fungi have been reported on this plant: Ctyospora acaciae, Diatryphe acaciae, Diplodia acaciae, Fomes badius, F. endotheius, F. fastuosus, F. rimosus, Fusicoccum indicum, Phyllactinia acaciae, Ravenelia acaciae-arabicae, Septogloeum acaciae, Septoria mortolensis, Sphaerostilbe acaciae. Trees are also parasitized by Dendrophthoe falcata and Loranthus globiferus var. verrucosus (Duke, 1981). In a survey for phytophagous insects on Acacia nilotica, 43 species were recorded in Pakistan, of these, 16 appeared stenophagous. The more promising for biological control of the tree were: Anarsia sp. cf. acaciae, Pseudosterrha paulula, Azanus ubaldus, and Ceutholopha isidis feeding on flowers; Bruchidius sahlbergi and Sulcobruchus sp. damaging seeds; Ascalenia callynella, Gisilia stereodoxa and an unidentified gracillariid boring shoots; and Cydia sp. making stem galls (Mohyuddin, 1981).

Yields and Economics

Various products of the tree are used locally in tropical Africa, blit none enter international markets. Trees usually add 2–3 cm in diameter each year (NAS, 1980).

References

• Ayoub, S.M.H. 1983. Algicidal properties of Acacia nilotica. Fitoterapia 53(5–6):175–8.
  
• Duke, 1981.
  
• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Duke, J.A. 1983a. Medicinal plants of the Bible. Trado-Medic Books, Owerri, NY.
  
• Mohyuddin, A.I. 1981. Phytophages associated with Acacia nilotica in Pakistan and possibilities of their introduction into Australia. p. 161–166. Proceedings of the 5th International Symposium on Biological Control of Weeds. Australia Commonwealth Scientific and Industrial Research Organization.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Pande, M.B., Talpada, P.M., Patel, J.S., and Shukla, P.C. 1981. Note on the nutritive value of babul (Acacia nilotica L.) seeds (extracted). In: Indian J. Anim. Sci. 51(1):107–108.
  
• Umalkar, C.V., Begum, S., Nehemiah, K.M.A. 1976. Inhibitory effect of Acacia nilotica extracts on pectolytic enzyme production by some pathogenic fungi. Indian Phytopath.: publ. 1977, 29(4):469–470.
  
• Walker, B.H. 1980. A review of browse and its role in livestock production in southern Africa. p. 7–24. In: LeHouerou, H.N. (ed.), Browse in Africa. International Livestock Centre for Africa. Addis Ababa, Ethiopia.

Acacia mearnsii de Wild

Uses

Tree of economic importance in South and East Africa, Rhodesia, India, and Rio Grande do Sul area of South America etc. for tanning of soft-leather. Ranging from 30–54 percent tannin in dried bark. Wood furnishes badly needed fuel and building material in some areas. Trees not only provide tannin and fuel, but also add nitrogen and organic material to improve the soil. Bark is used for wood adhesives and flotation agents (Duke, 1981a). The pulp is suitable for wrapping paper and hardboard. Some regard it as an attractive ornamental. Sometimes used for erosion control on poor sloping soils unsuitable for agriculture. Densely packed plantations are effective in preventing further erosion on 50° slopes. Some farmers claim that tobacco and vegetable yields are doubled in rotating with the black wattle. In places it is regarded as a "green cancer", spreading vigorously as a weed (NAS, 1980; Little, 1983).

Folk Medicine

Products are often used in folk medicine as styptics or astringents (Duke, 1981).

Chemistry

Black wattle bark contains (-)-robinetinidol and (+)-catechin; the biflavonoids (-)-fisetinidol-(+)-catechin (2 diastereoisomers), (-)-robinetinidol-(+)-catechin and (-)-robinetinidol-(+)-gallocatechin; triflavonoids and condensed tannins. The heartwood is rich in (+)-leucofisetinidin (mollisacacidin) together with (-)-fisetinidol, (+)-fustin, butin, fisetin, butein, and biflavonoid condensates (tannins) (Duke, 1981).

Description

Tree 6 to 20 m tall, 10 to 60 cm in diameter; crown conical or rounded; all parts except flowers usually pubescent or puberulous; stems without spines or prickles; leaves bipinnate, on petioles 1.5–2.5 cm long, with a gland above; rachis 4–12 cm long with numerous raised glands all along its upper side; pinnae in 8–30 pairs, pinnules in 16–70 pairs, linear-oblong, 1.5–4 mm long, 0.5–0.75 min wide; flowers in globose heads 5–8 mm in diameter, borne in panicles or racemes, on peduncles 2–6 mm long; pale yellow and fragrant; pods gray-puberulous, or sometimes glabrous, almost moniliform, dehiscing, usually 3–10 cm long, 0.5–0.8 cm wide, with 3–14 joints; seeds black, smooth, elliptic or compressed ovoid, 3–5 mm long, 2–3.5 mm wide; caruncle conspicuous; areole 3.5 mm long, 2 mm wide. Seeds 66,000 to 110,000/kg (Duke, 1981a).

Germplasm

Can be crossed with Acacia decurrens, hybrids show more sterility than parents. Meiosis is regular, with no gross cytological abnormalities, and sterility may be due to gene differentiation between species. There is little geographic overlap in the native Australian ranges of the species, and there are differences in phenology (flowering; seedset). Most of the characters that vary among the species are quantitative. The development of black wattle strains or of hybrids with enhanced vigor, better quality bark, outstanding stem form, or resistance to insect pests and disease would benefit the wattle industry. Assigned to the Australian Center of Diversity, black wattle or cvs thereof is reported to exhibit tolerance to drought, laterite, and poor soil (Duke, 1981). For an Acacia, it is relatively tolerant to frost, and its growth is slowed by high temperatures. (2n = 26.)

Distribution

Native to Southeast Australia (Victoria to New South Wales and southern Queensland) and Tasmania. Introduced and cultivated widely for afforestations. See Sherry (1971) for details.

Ecology

In Kenya grows on or near Equator at altitudes of 2,000–2,800 m, is well adjusted to the climate of East Africa. Grows well at 30°S Lat. in South America on rolling terrain at altitudes of 50–70 m. Thrives on poor, dry soils but favors deeper, moister, more fertile soils. In Australia, black wattle may occur on soils derived from shales, mudstones, sandstones, conglomerates, and alluvial deposits. In Kenya on podsols, krasnozems, sandy hills, lava flows or on mixtures of lava and contemporaneous volcanic tuffs and breccias. In South America, grown on red clay or sandy soils that have suffered from severe erosion and soil depletion (ferruginous clay loams with little or no free silica). In East Africa grows where annual rainfall is 1,041–1,321 mm, (about 75% between April and September). On the equator where black wattle is grown in South America, the rain pattern is nearly opposite, mean annual temperature range is 17–23°C; there is little seasonal variation, but considerable diurnal variation. At higher altitudes in South America, frost is a risk and heavy snows may break tree limbs. Tannin content varies inversely with precipitaton. Ranging from Warm Temperate Dry through Tropical Thorn to Tropical Moist Forest Life Zones, black wattle is reported to tolerate annual precipitation of 6.6–22.8 dm (mean of 6 cases=12.6), annual mean temperature of 14.7–27.8°C (mean of 6 cases=2.6°C), and pH of 5.0–7.2 (mean of 5 cases = 0.5).

Cultivation

Propagation by seed is easy. Seeds retain their viability for several years. For germination seed are covered with boiling water and allowed to stand until cool. This cracks the hard outer coat and facilitates germination. Seeds may be broadcast or sown in rows on any barren site. Usually they are sown about 5 cm apart in seedbeds, and are transplanted after 3–6 months. In South America, fields are usually plowed and harrowed in April or May. Seedlings are set out May–November, but usually in winter, June–August, after a rain. Plants are spaced 2 m each way, at rate of 2,500/ha. Propagation by cuttings is almost impossible without mist. Air layering is more promising. Two types of farmers grow acacia: the tanner or business man plants 200 ha or so entirely to black wattle, usually one section at a time so that he can plant and harvest within the same year and continue year after year; the farmer plants half or less of his land to black wattle and the rest to crops such as corn, beans, maniac, sugarcane, other vegetables, or pasture. He plants 2–6 hectares of acacian each year and thus evenly distributes work and production. Oxen may be useful for plowing, but most work is by hand. Usually only plows and hoes are used in Cultivation. Intercrops may be grown the first year during which trees grow about 4–5 m in height, and about 2.5 cm in diameter (Duke, 1981).

Harvesting

Trees provide bark 5–10 years after seeding (avg 7). Bark is stripped from lower part of tree, then tree is felled, the remaining bark removed, and tree and bark are cut into 1 m lengths. Thoroughly dried bark is arranged in bales of 75 to 80 kg when ready for transportation. Tanning power improves by 10–15% in bark carefully stored for a season. Percent tannin does not differ between barks harvested in dry and wet seasons. However, the amount of bark on trees may be less on poor than on rich soils. Tannin runs about 25–35% per kilo of dried bark, on either poor or rich soil. Acacia bark may be sold as baled bark, or bark powder. Dried bark may go first to commercial bark processors where it is ground or shredded in a hammermill, then sold in 40-kg sacks. Bark powder is sold in 60-kg sacks. Liquid extract is sold in 300-kg wooden barrels. In Rio Grande do Sul an estimated 5,000 MT of liquid extract is produced annually (Duke, 1981a).

Yields and Economics

Except for some mangrove species, black wattle in pure stand produces more tannin per hectare than most tanniniferous plants. In South Africa well-managed have produced the equivalent of 3 MT/ha tannin, about twice the average, when grown in rotations in excess of 12 years. One 7-yr-old tree produces 3–5 kg of dried bark. Twelve trees produce 1 cu m of firewood. The wood of debarked trees is dried and used for mine timbers, pulpwood, and fuel. Moisture loss is rapid in first 4 weeks after felling, then much slower. Wood weighs 708.7 kg/cu m. One tree can produce up to 10 cwt of bark or about 5 cwt stripped. One ton of black wattle bark is sufficient to tan 2,530 hides, best adapted for sole leather and other heavy goods; the leather is fully as durable as that tanned with oak bark. One ton of bark yields 4 cwt of extract tar. Destructive distillation of the wood yields 33.2% charcoal, 9.5% lime acetate, and 0.81 methyl alcohol. As a source of vegetable tannin, black wattle shares with quebracho and chestnut a large portion of the world market for vegetable tannins. According to Sherry (1971), plantation grown wattle in South Africa, Rhodesia, Tanzania, Kenya, and Brazil supplied about 38% of world demand for tannin. South Africa was the largest producer, with annual output of 72,000 MT of ca 120,000 MT on the world market. Eucalyptus grandis produces more wood than wattle, but it is inferior for fuel and charcoal. At one time in South Africa, 56% of the proceeds from wattle was from bark, the balance from timber (Duke, 1981a).

Energy

An efficient N-fixer, it is reported to annually yield 21–28 MT/ha wet leaves containing 245–285 kg N. If we put the information in our cultivation paragraph and our yields paragraph, we find the improbable 2,500 plants per hectare, with 12 producing 1 m³ firewood, suggesting a potential of more than 200 m³/ha for 7 year old trees, suggesting annual yields of ca 30 m³/ha. NAS (1980a) reports annual thickwood production of 10–25 m°3/ha and bark production of 0.8–4.0 MT. The dense wood (sp. grav. = 0.7–0.85) 3,500–4,000 kcal/kg (oven-dry Indonesian specimens 4,650 kcal/kg), its ash content ca 1.5%. The charcoal (sp. grav. = 0.3–0.5) has a calorific value of 6,600 kcal/kg, with an ash content of 0.4%.

Biotic Factors

The most serious disease is disback, caused by Phoma herbarum. Other fungi attacking black wattle include: Chaetomium cochliodes, Daldinia sp., and Trichoderma viride. In Rio Grande do Sul, disease and insects cause about 20% loss of trees. Principal insects attacking Brazilian wattle are Molippa sabina, Achryson surinamum, Placosternus cyclene, Eburodacrys dubitata, Neoclytus pusillus, Oncideres impluviata, Oncideres saga, and Trachyderes thoracica. Ants, termites, and borers are the most damaging. The sauva ant which attacks the leaves is fought constantly with arsenicals and carbon disulfide. Nematodes reported on this species include Meloidogyne arenaria, M. incognita acrita, and M. javanica (Golden, pers. commun. 1984).

References

• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Little, E.L. Jr. 1983. Common fuelwood crops: a handbook for their identification. McClain Printing Co., Parsons, WV.
  
• NAS, 1980.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Sherry, S.P. 1971. The black wattle (Acacia mearnsii de Wild.). University of Natal Press. Pietermatitzburg.

Acacia mearnsii de Wild

Uses

Tree of economic importance in South and East Africa, Rhodesia, India, and Rio Grande do Sul area of South America etc. for tanning of soft-leather. Ranging from 30–54 percent tannin in dried bark. Wood furnishes badly needed fuel and building material in some areas. Trees not only provide tannin and fuel, but also add nitrogen and organic material to improve the soil. Bark is used for wood adhesives and flotation agents (Duke, 1981a). The pulp is suitable for wrapping paper and hardboard. Some regard it as an attractive ornamental. Sometimes used for erosion control on poor sloping soils unsuitable for agriculture. Densely packed plantations are effective in preventing further erosion on 50° slopes. Some farmers claim that tobacco and vegetable yields are doubled in rotating with the black wattle. In places it is regarded as a "green cancer", spreading vigorously as a weed (NAS, 1980; Little, 1983).

Folk Medicine

Products are often used in folk medicine as styptics or astringents (Duke, 1981).

Chemistry

Black wattle bark contains (-)-robinetinidol and (+)-catechin; the biflavonoids (-)-fisetinidol-(+)-catechin (2 diastereoisomers), (-)-robinetinidol-(+)-catechin and (-)-robinetinidol-(+)-gallocatechin; triflavonoids and condensed tannins. The heartwood is rich in (+)-leucofisetinidin (mollisacacidin) together with (-)-fisetinidol, (+)-fustin, butin, fisetin, butein, and biflavonoid condensates (tannins) (Duke, 1981).

Description

Tree 6 to 20 m tall, 10 to 60 cm in diameter; crown conical or rounded; all parts except flowers usually pubescent or puberulous; stems without spines or prickles; leaves bipinnate, on petioles 1.5–2.5 cm long, with a gland above; rachis 4–12 cm long with numerous raised glands all along its upper side; pinnae in 8–30 pairs, pinnules in 16–70 pairs, linear-oblong, 1.5–4 mm long, 0.5–0.75 min wide; flowers in globose heads 5–8 mm in diameter, borne in panicles or racemes, on peduncles 2–6 mm long; pale yellow and fragrant; pods gray-puberulous, or sometimes glabrous, almost moniliform, dehiscing, usually 3–10 cm long, 0.5–0.8 cm wide, with 3–14 joints; seeds black, smooth, elliptic or compressed ovoid, 3–5 mm long, 2–3.5 mm wide; caruncle conspicuous; areole 3.5 mm long, 2 mm wide. Seeds 66,000 to 110,000/kg (Duke, 1981a).

Germplasm

Can be crossed with Acacia decurrens, hybrids show more sterility than parents. Meiosis is regular, with no gross cytological abnormalities, and sterility may be due to gene differentiation between species. There is little geographic overlap in the native Australian ranges of the species, and there are differences in phenology (flowering; seedset). Most of the characters that vary among the species are quantitative. The development of black wattle strains or of hybrids with enhanced vigor, better quality bark, outstanding stem form, or resistance to insect pests and disease would benefit the wattle industry. Assigned to the Australian Center of Diversity, black wattle or cvs thereof is reported to exhibit tolerance to drought, laterite, and poor soil (Duke, 1981). For an Acacia, it is relatively tolerant to frost, and its growth is slowed by high temperatures. (2n = 26.)

Distribution

Native to Southeast Australia (Victoria to New South Wales and southern Queensland) and Tasmania. Introduced and cultivated widely for afforestations. See Sherry (1971) for details.

Ecology

In Kenya grows on or near Equator at altitudes of 2,000–2,800 m, is well adjusted to the climate of East Africa. Grows well at 30°S Lat. in South America on rolling terrain at altitudes of 50–70 m. Thrives on poor, dry soils but favors deeper, moister, more fertile soils. In Australia, black wattle may occur on soils derived from shales, mudstones, sandstones, conglomerates, and alluvial deposits. In Kenya on podsols, krasnozems, sandy hills, lava flows or on mixtures of lava and contemporaneous volcanic tuffs and breccias. In South America, grown on red clay or sandy soils that have suffered from severe erosion and soil depletion (ferruginous clay loams with little or no free silica). In East Africa grows where annual rainfall is 1,041–1,321 mm, (about 75% between April and September). On the equator where black wattle is grown in South America, the rain pattern is nearly opposite, mean annual temperature range is 17–23°C; there is little seasonal variation, but considerable diurnal variation. At higher altitudes in South America, frost is a risk and heavy snows may break tree limbs. Tannin content varies inversely with precipitaton. Ranging from Warm Temperate Dry through Tropical Thorn to Tropical Moist Forest Life Zones, black wattle is reported to tolerate annual precipitation of 6.6–22.8 dm (mean of 6 cases=12.6), annual mean temperature of 14.7–27.8°C (mean of 6 cases=2.6°C), and pH of 5.0–7.2 (mean of 5 cases = 0.5).

Cultivation

Propagation by seed is easy. Seeds retain their viability for several years. For germination seed are covered with boiling water and allowed to stand until cool. This cracks the hard outer coat and facilitates germination. Seeds may be broadcast or sown in rows on any barren site. Usually they are sown about 5 cm apart in seedbeds, and are transplanted after 3–6 months. In South America, fields are usually plowed and harrowed in April or May. Seedlings are set out May–November, but usually in winter, June–August, after a rain. Plants are spaced 2 m each way, at rate of 2,500/ha. Propagation by cuttings is almost impossible without mist. Air layering is more promising. Two types of farmers grow acacia: the tanner or business man plants 200 ha or so entirely to black wattle, usually one section at a time so that he can plant and harvest within the same year and continue year after year; the farmer plants half or less of his land to black wattle and the rest to crops such as corn, beans, maniac, sugarcane, other vegetables, or pasture. He plants 2–6 hectares of acacian each year and thus evenly distributes work and production. Oxen may be useful for plowing, but most work is by hand. Usually only plows and hoes are used in Cultivation. Intercrops may be grown the first year during which trees grow about 4–5 m in height, and about 2.5 cm in diameter (Duke, 1981).

Harvesting

Trees provide bark 5–10 years after seeding (avg 7). Bark is stripped from lower part of tree, then tree is felled, the remaining bark removed, and tree and bark are cut into 1 m lengths. Thoroughly dried bark is arranged in bales of 75 to 80 kg when ready for transportation. Tanning power improves by 10–15% in bark carefully stored for a season. Percent tannin does not differ between barks harvested in dry and wet seasons. However, the amount of bark on trees may be less on poor than on rich soils. Tannin runs about 25–35% per kilo of dried bark, on either poor or rich soil. Acacia bark may be sold as baled bark, or bark powder. Dried bark may go first to commercial bark processors where it is ground or shredded in a hammermill, then sold in 40-kg sacks. Bark powder is sold in 60-kg sacks. Liquid extract is sold in 300-kg wooden barrels. In Rio Grande do Sul an estimated 5,000 MT of liquid extract is produced annually (Duke, 1981a).

Yields and Economics

Except for some mangrove species, black wattle in pure stand produces more tannin per hectare than most tanniniferous plants. In South Africa well-managed have produced the equivalent of 3 MT/ha tannin, about twice the average, when grown in rotations in excess of 12 years. One 7-yr-old tree produces 3–5 kg of dried bark. Twelve trees produce 1 cu m of firewood. The wood of debarked trees is dried and used for mine timbers, pulpwood, and fuel. Moisture loss is rapid in first 4 weeks after felling, then much slower. Wood weighs 708.7 kg/cu m. One tree can produce up to 10 cwt of bark or about 5 cwt stripped. One ton of black wattle bark is sufficient to tan 2,530 hides, best adapted for sole leather and other heavy goods; the leather is fully as durable as that tanned with oak bark. One ton of bark yields 4 cwt of extract tar. Destructive distillation of the wood yields 33.2% charcoal, 9.5% lime acetate, and 0.81 methyl alcohol. As a source of vegetable tannin, black wattle shares with quebracho and chestnut a large portion of the world market for vegetable tannins. According to Sherry (1971), plantation grown wattle in South Africa, Rhodesia, Tanzania, Kenya, and Brazil supplied about 38% of world demand for tannin. South Africa was the largest producer, with annual output of 72,000 MT of ca 120,000 MT on the world market. Eucalyptus grandis produces more wood than wattle, but it is inferior for fuel and charcoal. At one time in South Africa, 56% of the proceeds from wattle was from bark, the balance from timber (Duke, 1981a).

Energy

An efficient N-fixer, it is reported to annually yield 21–28 MT/ha wet leaves containing 245–285 kg N. If we put the information in our cultivation paragraph and our yields paragraph, we find the improbable 2,500 plants per hectare, with 12 producing 1 m³ firewood, suggesting a potential of more than 200 m³/ha for 7 year old trees, suggesting annual yields of ca 30 m³/ha. NAS (1980a) reports annual thickwood production of 10–25 m°3/ha and bark production of 0.8–4.0 MT. The dense wood (sp. grav. = 0.7–0.85) 3,500–4,000 kcal/kg (oven-dry Indonesian specimens 4,650 kcal/kg), its ash content ca 1.5%. The charcoal (sp. grav. = 0.3–0.5) has a calorific value of 6,600 kcal/kg, with an ash content of 0.4%.

Biotic Factors

The most serious disease is disback, caused by Phoma herbarum. Other fungi attacking black wattle include: Chaetomium cochliodes, Daldinia sp., and Trichoderma viride. In Rio Grande do Sul, disease and insects cause about 20% loss of trees. Principal insects attacking Brazilian wattle are Molippa sabina, Achryson surinamum, Placosternus cyclene, Eburodacrys dubitata, Neoclytus pusillus, Oncideres impluviata, Oncideres saga, and Trachyderes thoracica. Ants, termites, and borers are the most damaging. The sauva ant which attacks the leaves is fought constantly with arsenicals and carbon disulfide. Nematodes reported on this species include Meloidogyne arenaria, M. incognita acrita, and M. javanica (Golden, pers. commun. 1984).

References

• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Little, E.L. Jr. 1983. Common fuelwood crops: a handbook for their identification. McClain Printing Co., Parsons, WV.
  
• NAS, 1980.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Sherry, S.P. 1971. The black wattle (Acacia mearnsii de Wild.). University of Natal Press. Pietermatitzburg.

Acacia mearnsii de Wild

Uses

Tree of economic importance in South and East Africa, Rhodesia, India, and Rio Grande do Sul area of South America etc. for tanning of soft-leather. Ranging from 30–54 percent tannin in dried bark. Wood furnishes badly needed fuel and building material in some areas. Trees not only provide tannin and fuel, but also add nitrogen and organic material to improve the soil. Bark is used for wood adhesives and flotation agents (Duke, 1981a). The pulp is suitable for wrapping paper and hardboard. Some regard it as an attractive ornamental. Sometimes used for erosion control on poor sloping soils unsuitable for agriculture. Densely packed plantations are effective in preventing further erosion on 50° slopes. Some farmers claim that tobacco and vegetable yields are doubled in rotating with the black wattle. In places it is regarded as a "green cancer", spreading vigorously as a weed (NAS, 1980; Little, 1983).

Folk Medicine

Products are often used in folk medicine as styptics or astringents (Duke, 1981).

Chemistry

Black wattle bark contains (-)-robinetinidol and (+)-catechin; the biflavonoids (-)-fisetinidol-(+)-catechin (2 diastereoisomers), (-)-robinetinidol-(+)-catechin and (-)-robinetinidol-(+)-gallocatechin; triflavonoids and condensed tannins. The heartwood is rich in (+)-leucofisetinidin (mollisacacidin) together with (-)-fisetinidol, (+)-fustin, butin, fisetin, butein, and biflavonoid condensates (tannins) (Duke, 1981).

Description

Tree 6 to 20 m tall, 10 to 60 cm in diameter; crown conical or rounded; all parts except flowers usually pubescent or puberulous; stems without spines or prickles; leaves bipinnate, on petioles 1.5–2.5 cm long, with a gland above; rachis 4–12 cm long with numerous raised glands all along its upper side; pinnae in 8–30 pairs, pinnules in 16–70 pairs, linear-oblong, 1.5–4 mm long, 0.5–0.75 min wide; flowers in globose heads 5–8 mm in diameter, borne in panicles or racemes, on peduncles 2–6 mm long; pale yellow and fragrant; pods gray-puberulous, or sometimes glabrous, almost moniliform, dehiscing, usually 3–10 cm long, 0.5–0.8 cm wide, with 3–14 joints; seeds black, smooth, elliptic or compressed ovoid, 3–5 mm long, 2–3.5 mm wide; caruncle conspicuous; areole 3.5 mm long, 2 mm wide. Seeds 66,000 to 110,000/kg (Duke, 1981a).

Germplasm

Can be crossed with Acacia decurrens, hybrids show more sterility than parents. Meiosis is regular, with no gross cytological abnormalities, and sterility may be due to gene differentiation between species. There is little geographic overlap in the native Australian ranges of the species, and there are differences in phenology (flowering; seedset). Most of the characters that vary among the species are quantitative. The development of black wattle strains or of hybrids with enhanced vigor, better quality bark, outstanding stem form, or resistance to insect pests and disease would benefit the wattle industry. Assigned to the Australian Center of Diversity, black wattle or cvs thereof is reported to exhibit tolerance to drought, laterite, and poor soil (Duke, 1981). For an Acacia, it is relatively tolerant to frost, and its growth is slowed by high temperatures. (2n = 26.)

Distribution

Native to Southeast Australia (Victoria to New South Wales and southern Queensland) and Tasmania. Introduced and cultivated widely for afforestations. See Sherry (1971) for details.

Ecology

In Kenya grows on or near Equator at altitudes of 2,000–2,800 m, is well adjusted to the climate of East Africa. Grows well at 30°S Lat. in South America on rolling terrain at altitudes of 50–70 m. Thrives on poor, dry soils but favors deeper, moister, more fertile soils. In Australia, black wattle may occur on soils derived from shales, mudstones, sandstones, conglomerates, and alluvial deposits. In Kenya on podsols, krasnozems, sandy hills, lava flows or on mixtures of lava and contemporaneous volcanic tuffs and breccias. In South America, grown on red clay or sandy soils that have suffered from severe erosion and soil depletion (ferruginous clay loams with little or no free silica). In East Africa grows where annual rainfall is 1,041–1,321 mm, (about 75% between April and September). On the equator where black wattle is grown in South America, the rain pattern is nearly opposite, mean annual temperature range is 17–23°C; there is little seasonal variation, but considerable diurnal variation. At higher altitudes in South America, frost is a risk and heavy snows may break tree limbs. Tannin content varies inversely with precipitaton. Ranging from Warm Temperate Dry through Tropical Thorn to Tropical Moist Forest Life Zones, black wattle is reported to tolerate annual precipitation of 6.6–22.8 dm (mean of 6 cases=12.6), annual mean temperature of 14.7–27.8°C (mean of 6 cases=2.6°C), and pH of 5.0–7.2 (mean of 5 cases = 0.5).

Cultivation

Propagation by seed is easy. Seeds retain their viability for several years. For germination seed are covered with boiling water and allowed to stand until cool. This cracks the hard outer coat and facilitates germination. Seeds may be broadcast or sown in rows on any barren site. Usually they are sown about 5 cm apart in seedbeds, and are transplanted after 3–6 months. In South America, fields are usually plowed and harrowed in April or May. Seedlings are set out May–November, but usually in winter, June–August, after a rain. Plants are spaced 2 m each way, at rate of 2,500/ha. Propagation by cuttings is almost impossible without mist. Air layering is more promising. Two types of farmers grow acacia: the tanner or business man plants 200 ha or so entirely to black wattle, usually one section at a time so that he can plant and harvest within the same year and continue year after year; the farmer plants half or less of his land to black wattle and the rest to crops such as corn, beans, maniac, sugarcane, other vegetables, or pasture. He plants 2–6 hectares of acacian each year and thus evenly distributes work and production. Oxen may be useful for plowing, but most work is by hand. Usually only plows and hoes are used in Cultivation. Intercrops may be grown the first year during which trees grow about 4–5 m in height, and about 2.5 cm in diameter (Duke, 1981).

Harvesting

Trees provide bark 5–10 years after seeding (avg 7). Bark is stripped from lower part of tree, then tree is felled, the remaining bark removed, and tree and bark are cut into 1 m lengths. Thoroughly dried bark is arranged in bales of 75 to 80 kg when ready for transportation. Tanning power improves by 10–15% in bark carefully stored for a season. Percent tannin does not differ between barks harvested in dry and wet seasons. However, the amount of bark on trees may be less on poor than on rich soils. Tannin runs about 25–35% per kilo of dried bark, on either poor or rich soil. Acacia bark may be sold as baled bark, or bark powder. Dried bark may go first to commercial bark processors where it is ground or shredded in a hammermill, then sold in 40-kg sacks. Bark powder is sold in 60-kg sacks. Liquid extract is sold in 300-kg wooden barrels. In Rio Grande do Sul an estimated 5,000 MT of liquid extract is produced annually (Duke, 1981a).

Yields and Economics

Except for some mangrove species, black wattle in pure stand produces more tannin per hectare than most tanniniferous plants. In South Africa well-managed have produced the equivalent of 3 MT/ha tannin, about twice the average, when grown in rotations in excess of 12 years. One 7-yr-old tree produces 3–5 kg of dried bark. Twelve trees produce 1 cu m of firewood. The wood of debarked trees is dried and used for mine timbers, pulpwood, and fuel. Moisture loss is rapid in first 4 weeks after felling, then much slower. Wood weighs 708.7 kg/cu m. One tree can produce up to 10 cwt of bark or about 5 cwt stripped. One ton of black wattle bark is sufficient to tan 2,530 hides, best adapted for sole leather and other heavy goods; the leather is fully as durable as that tanned with oak bark. One ton of bark yields 4 cwt of extract tar. Destructive distillation of the wood yields 33.2% charcoal, 9.5% lime acetate, and 0.81 methyl alcohol. As a source of vegetable tannin, black wattle shares with quebracho and chestnut a large portion of the world market for vegetable tannins. According to Sherry (1971), plantation grown wattle in South Africa, Rhodesia, Tanzania, Kenya, and Brazil supplied about 38% of world demand for tannin. South Africa was the largest producer, with annual output of 72,000 MT of ca 120,000 MT on the world market. Eucalyptus grandis produces more wood than wattle, but it is inferior for fuel and charcoal. At one time in South Africa, 56% of the proceeds from wattle was from bark, the balance from timber (Duke, 1981a).

Energy

An efficient N-fixer, it is reported to annually yield 21–28 MT/ha wet leaves containing 245–285 kg N. If we put the information in our cultivation paragraph and our yields paragraph, we find the improbable 2,500 plants per hectare, with 12 producing 1 m³ firewood, suggesting a potential of more than 200 m³/ha for 7 year old trees, suggesting annual yields of ca 30 m³/ha. NAS (1980a) reports annual thickwood production of 10–25 m°3/ha and bark production of 0.8–4.0 MT. The dense wood (sp. grav. = 0.7–0.85) 3,500–4,000 kcal/kg (oven-dry Indonesian specimens 4,650 kcal/kg), its ash content ca 1.5%. The charcoal (sp. grav. = 0.3–0.5) has a calorific value of 6,600 kcal/kg, with an ash content of 0.4%.

Biotic Factors

The most serious disease is disback, caused by Phoma herbarum. Other fungi attacking black wattle include: Chaetomium cochliodes, Daldinia sp., and Trichoderma viride. In Rio Grande do Sul, disease and insects cause about 20% loss of trees. Principal insects attacking Brazilian wattle are Molippa sabina, Achryson surinamum, Placosternus cyclene, Eburodacrys dubitata, Neoclytus pusillus, Oncideres impluviata, Oncideres saga, and Trachyderes thoracica. Ants, termites, and borers are the most damaging. The sauva ant which attacks the leaves is fought constantly with arsenicals and carbon disulfide. Nematodes reported on this species include Meloidogyne arenaria, M. incognita acrita, and M. javanica (Golden, pers. commun. 1984).

References

• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Little, E.L. Jr. 1983. Common fuelwood crops: a handbook for their identification. McClain Printing Co., Parsons, WV.
  
• NAS, 1980.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Sherry, S.P. 1971. The black wattle (Acacia mearnsii de Wild.). University of Natal Press. Pietermatitzburg.