DISTRIBUTION
Widespread in Tanzania throughout the woodland in the coastal plain; in savannah woodlands and grasslands in Kilwa, Lindi, Morogoro, and Tabora (RSCU 1992); in Miombo savannah and in Miombo dry forests as scattered trees. It is found in the north to Lake Victoria (Borota 1975). It probably prefers sites with more alkaline soils and an open understorey.
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Minimum Altitude (m): |
0 |
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Maximum Altitude (m): |
1650 |
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Minimum Rainfall (mm): |
700 |
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Maximum Rainfall (mm): |
1500 |
REQUIREMENTS
Soil Requirements: Adaptable to red loams and deep sandy soils, but not coastal sands or black clays. Prefers soils whose physical characteristics permit water to rapidly drain down the profile, at least through the top 30 cm (Boaler 1966).
Light Requirements: Demanding.
Influential Factors: P. angolensis is able to survive annual fires after the tree has reached pole size. It is sensitive to frost. Young seedlings may be susceptible to termites and crickets (Borota 1975).
PROPAGATION
Means of Propagation: Seedlings and stumps.
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Seeds per kg: |
4200 |
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Germination Rate: |
50 |
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Seed Sources: |
4000 TSH per kg - Tanzania National Seed Centre 1991. |
Seed Treatments: Pods are winged, disc-shaped with a diameter of 8 to 10 cm, and contain 1 or 2 seeds. The pods do not split open, and must be opened manually. Boaler notes that it is difficult to open the pods without damaging the seeds (1966). Seed which has been filed or scarified germinates more readily than untreated seed, but even this may have limited results. Chipping the fruit at one edge hastens germination (Nwoboshi, 1982). Repeated wetting and drying induces fruit opening, after which the seed will germinate inside the open fruit (Boaler 1966). Burning may also assist fruit opening and germination. About 50% of Pterocarpus fruits contain seed and the remainder are barren.
Seedling Management: It is reported that cuttings grow well but that they must be planted when the sap is rising (October in southern Africa) (Palmer and Pitman 1972). Boaler (1966) reports 0 to 30% success by vegetative propagation. Best success occurred when using young, vigorous shoots cut and put into the ground, just before the prerain flush in September in Tanzania. Such cuttings need regular watering after planting.
Nursery stock can be left to develop to striplings or to bare-rooted stock with a long shoot of 1 to 2 m. The root system is only slightly pruned off. Seedlings are stripped of leaves before transporting to the planting site in order to reduce transpiration losses (Nwoboshi 1982).
SILVICULTURE
Planting Types: Grown in woodlots, plantations, and around homes as live fences.
Growth Factors: Slow growth is reported in Dodoma.
Growth Cycle: The tree has a rotation length of 40 to 75 years. Life expectancy is 60 to 90 years. P. angolensis begins to produce fruit at about 20 years of age, but fruiting is light until 35 years. Trees will continue to produce fruit until they die (Boaler 1966). Fruits are collected from the ground from August through October.
Management Systems: Site preparation requires clear cutting, control of fire and of competition for the first 10 years of the plantation (Boaler 1966). Spacing in a pure stand should not be closer than 5×5 m.
In the seedling stage, the above ground parts of the plant die back each year until the root system has grown sufficiently to support a shoot capable of surviving the dry season. Shoots rarely grow more than 15 cm. This makes using the species difficult in plantation forestry (Boaler 1966). Boaler lists 4 external conditions necessary for the most rapid growth from seedling to sapling: full light, absence of fire, no root competition, and adequate supply of mineral nutrients. Annual burning is said to slow the development of seedlings but promotes sapling growth.
IMPORTANT USES
Use #1: TIMBER
One of the best known, most generally used and most valuable of all woods in southern tropical Africa. Very durable, strong, medium hard and dense, it is easy to work, (Borota 1975) and is heavily exploited. It is used as a general purpose timber, for furniture, boat construction, for poles, and occasionally for firewood.
Use #2: MEDICINE
It is used to treat numerous diseases throughout Africa. The root is believed to cure malaria, black water fever, and gonorrhoea (Palgrave 1988). The bark is used as a general purpose treatment for headaches, stomach aches, mouth sores, and rashes.
Use #3: LAND IMPROVEMENT
P. angolensis is nitrogen fixing and is used for soil conservation, dune fixation, and as an ornamental. Leaves and shoots are also used as fodder and it is regarded as a good bee plant.
