Acrocarpus grandis (Miq.) Miq.

Acrocarpus fraxinifolius is a stately deciduous tree, attaining heights of 30-60 m; stem cylindrical, free of branches for up to 75% of its total height. Even above its massive plank buttresses, it can achieve a diameter of over 200 cm. The branches remain relatively thin and are horizontally deployed. Bark is thin and light grey in colour. Although a legume, it apparently does not have nitrogen-fixing nodules. A. fraxinifolius is deep rooting, sometimes upto 4.5 m into the soil. Leaves bipinnate, about 30 cm with 3-4 compound leaflets and consisting of 5-6 elliptical, lanceolate leaflets 7-10 cm long and arranged in pairs; bright red when young, giving the tree its characteristic appearance. Flowers appear on tree when leafless, up to 20 dense heads hanging down from branch ends, each 12 cm long, dripping nectar from the reddish-green to orange flowers. Fruit an elongated and flattened pod, long-stipitate, narrowly winged; (min. 3) 10-18 seeded. Seed slightly lens shaped, brown.

The bisexual flowers are produced after shedding its leaves. In India, flowering and fruiting occur almost every year.

Grows best in deep, well-drained, clayey loam soils with a pH of 4-7. It l also thrives in shallow and compacted soils.

A. fraxinifolius grows best in submontane areas in the humid and subhumid tropics with a short, dry spell. It is very sensitive to frost. In Thailand, it occurs in evergreen gallery forest and is more frequent in India and Myanmar. Regenerates primarily in small, burnt areas, on open patches where fresh soil has been exposed and along newly constructed roads. A. fraxinifolius is a pioneer and demands light, but it can tolerate slight shade when young. It is most suitable for moderate altitudes with red soil and a moist climate.

A. fraxinifolius is planted in many areas within and outside its natural area of distribution. It was introduced into Tanzania as a plantation tree, originally in Lushoto and Tabora and later throughout Tanzania. In Uganda, it was originally introduced in arboreta and later planted throughout the country.

A. fraxinifolius is propagated by seed; the use of wildings has been reported in India. Patch budding has been used and 80% success recorded during establishment seed orchards. Seed should be pretreated with sulphuric acid for 10 min, or with hot water and left to soak for 24 hours before being sown in a shaded bed. A germination of 80-95% within only 2-7 days is achieved after this pretreatment. Under natural conditions, some seeds may germinate within a week, while others may lie dormant for a year before germinating. Seedlings are ready for planting out when 3 months old and 30-45 cm tall. The seedlings are pricked out into beds or containers and placed in full sunlight. From the beds they can be planted bare-rooted or as stumps or striplings.

In India, to ensure sufficient natural regeneration of this light-demanding species, the forest floor is cleared of weeds and raked, after which the canopy is gradually removed as young trees become established. Frequent tending is required until the crowns of the young trees close. Periodic weeding is required until they are well into their sapling stage; the 1st thinning should be performed 3-4 years after planting. As the tree requires a large crown for optimal growth, regular thinning is necessary until the stand is fully developed. On favourable sites, a mean annual increment of 10 cubic m/ha may be expected. In Malawi, 2-year-old trees yielded 33 t/ha of total aboveground biomass. A. fraxinifolius coppices vigorously. Rotation period for fuel is 8-10 years and for timber 30-40 years. The tree should not be planted near houses as dry branches drop off. Competes with crops if grown in fields.

So far, a few incidences of pests or diseases have been observed in A. fraxinifolius. Young trees are susceptible to termite attack, and in India Atractomorpha crenulata, a grasshopper, and the caterpillar of Eurema blanda defoliate seedlings in nurseries and young plantations. The tree is also a host for the wood borer Xylosandrus compactus, a small Ambrosia beetle. Ganoderma lucidum causes trunk and root rot wherever A. fraxinifolius is cultivated.

Seeds exhibit orthodox storage behaviour; seeds should be stored at low temperatures. A few seeds survived 7 years of storage at room temperature (Hong TD et al.,1996). There are about 13 000-47 000 seeds/kg.

Erosion control: A. fraxinifolius has been recommended for reinforcing riverbanks and stabilizing terraces. Shade or shelter: Ideal as a shade tree on tea and coffee plantations, for example, as planted in Kenya and Uganda. Known to have been planted as a windbreak in Tanzania. Reclamation: Very good for reforestation of open areas. Soil improver: Leaves are suitable for mulching.

Fodder: The foliage can be used as fodder. Apiculture: A. fraxinifolius is a good source of nectar and a good bee forage. Fuel: The wood is sometimes used for firewood in many places. Timber: The sapwood is whitish; the heartwood is bright red to brownish-red with darker veins, making it very decorative. The wood is not very durable and is prone to attack by fungi and insects, but it impregnates well. It is heavy, moderately hard, and compact; specific gravity varies between 0.55 and 0.7 g/cubic cm. It is easy to work with tools and is well suited for turnery, carving and polishing. The wood is used for interior trim, panelling, furniture and cabinet work. Within its native range it is also used for shingles, general construction, floors, stairways, doors, tea crates, beehive frames, and after being impregnated, for railway ties. Gum or resin: The wood exudes a gumlike resin when the trees are felled.