The Neem tree (Azadirachta indica)
Neem (Azadirachta indica, syn. Melia azadirachta L., Antelaea azadirachta (L.) Adelb.) is a tree in the mahogany family Meliaceae.
Neem is a fast-growing tree that can reach a height of 15-20 m (about 50-65 feet), rarely to 35-40 m (115-131 feet). It is evergreen but in severe drought it may shed most or nearly all of its leaves. The branches are wide spread. The fairly dense crown is roundish or oval and may reach the diameter of 15-20 m in old, free-standing specimens.
The neem tree is noted for its drought resistance. Normally it thrives in areas with sub-arid to sub-humid conditions, with an annual rainfall between 400 and 1200 mm. Neem can grow in many different types of soil, but it thrives best on well drained deep and sandy soils. It is a typical tropical to subtropical tree and exists at annual mean temperatures between 21-32 °C. It can tolerate high to very high temperatures and does not tolerate temperature below 4 °C.
A single tree can yield up to 50 kg fruit (National Academy of Sciences 1992) and may live two centuries. Duke (1993) estimates annual productivity of 2-21 tonnes/ha.
Seeds of the Neem tree contain approximately 20 to 45% oil with the following fatty acid composition:
- 53% Oleic
- 18% Stearic
- 14% Palmitic
Small amounts of linoleic and arachidic acid can also be found (Duke and duCellier, 1993).
The gum exuding from the bark contains 13-15% water, 3% ash, 12% galactans, 25% pentosans, with some albumins and oxidase.
Fruits contain the toxic alkaloid azaridin. According to USDA reports low doses (0.1 ppm) of a Neem extract called azadirachtin protected plant leaves from Coleopteras, while control leaves were completely destroyed by beetles. Wheat, barley, rice, sugar cane, tomatoes, cotton and chrysanthemums were protected from insect damage for 10 weeks after 1% Neem dust was applied to the soil in which the plants were growing. The systemic protection persisted despite heavy rains.
