Azadirachta indica Juss.

Meliaceae

Common name(s):

Neem tree, Indian lilac, Margosa tree

Description:

A small, easily identifiable tree with a straight stem, which may exceptionally reach a height of 20 m. The bark is dark-grey, fairly thick, with many longitudinal and oblique crevices which are lighter in colour. The inner surface of the bark is reddish-brown. The sap-wood is greyish-white while the heart-wood is red, but becomes brownish when exposed. It is a hard, fragrant lasting wood which sometimes is somewhat shiny, especially when radially cut. It is fairly unevenly textured and moderately heavy. It resembles the mahogany Swietenia mahogani. Density is 0.68, but weight may vary from 35-53 lb./cu.ft. The wood is durable even in exposed conditions, and is not affected by termites or canker worms. The wood can withstand hand or mechanical working, is good for carving, but does not attain a fine polish. Branches are widely spread and make an oval-shaped crown. Leaves, pale-green on poor soil or when young, but dark glossy green when adult, are glabrous, unequally pinnate, alternate and stipulate.  They may reach 35 cm in length. Petioles are supple; leaflets are alternate or opposite and may reach 8 cm in length. They are ovate, lanceolate, attenuated at the tip and unequal at the base, with the upper part longer than the lower. The leaflet is more or less sickle-shaped and slightly denticulate. Flowers are white, pleasantly fragrant, small and hermaphrodite.  Peduncles are short and panicules axillary. Bracteae are small and deciduous.  The calyx is round and imbricate with smooth sepals. The corolla, with five imbricate oblong petals, reaches 0.4 cm in length. Ten stamens fixed at the base of a disc form a long cylindrical pipe. The gynaecium is syncarpic with 3-5 carpels; there are two ovules in each locule. The stigma is 5-lobed, chromosomic number 14. There are haploid individuals. The fruit is a small drupe, ellipsoid in shape, about 2 cm long, yellow-green when ripe with one stone and one or sometimes two seeds. There are about 4 000 clean seeds to the kg. Germination rate is around 75%.

Distribution:

The original habitat of Neem is the dry open bush forest of Burma (Myanmar).  It can also be found wild in India on the Siwalik hills and perhaps also in the forests of the Carnate region and some parts of the Deccan to the south of the Gadavari River.  The species, however, is cultivated everywhere in India and Burma, especially in dry regions. It obviously became acclimatized in many regions where one may find numerous individual trees which have become sub-spontaneous although of cultivated origin. The Neem is the most commonly planted species in the Sudanese ecological zone of Nigeria, and is much used in the Sudan, especially in the villages of the Sahelian ecological zone.

Propagation:

Broadcast seeding on ploughed land does not yield good results. Plantation in 8 x 8 m pits is recommended. Usually deep parallel furrows 8 m apart are used. Three de-pulped fruits are planted every 8 m in these furrows.  The seed would readily germinate on top of the soil, but should be slightly buried to reduce damage from insects and rodents. Thinning is carried out later, in order to leave one seedling every 8 m. The whole operation must be done rapidly, since seed viability lasts only 1-2 weeks. One may use seedlings grown in a nursery, either for replacement or for the whole plantation, but difficulty may be experienced with the root system in some individuals or in some clones. Roots must be frequently trimmed around and under each seedling while in the nursery. In West Africa, however, it seems that the root system is not so rapidly developed, since bare-rooted nursery seedlings, aged 35-40 weeks, are being used. 

Management:

A system of planting often adopted by tenant farmers in India is as follows:  The land is cropped in the first year by the tenant farmer; but in the second year, he must plant rows of Neem, spaced about 130 cm apart; in the third year, alternate rows are thinned out and planted in another field. Tree rows are now spaced 2.60 m. In the fourth year, three rows out of four are eliminated, which leaves a plantation with a spacing of 10.4 m in-between rows. 

Products and uses:

The wood is used to make carts, farm tools or even furniture. The heart-wood is very rich in tannin and in inorganic salts of calcium, potassium and iron. Nimatone, a turpentine-like liquid, and also a glossy resin, may be extracted from it. Many Neem extracts are effective against a large range of crop pests. Various insect-repellent products are extracted from the oil. The active principal in those products is Azidarachtine. The bark, leaves and fruit have been, from time immemorial, part of the Hindu pharmacopoeia; used for treating all sorts of ailments, from syphilis to leprosy to rheumatism. Neem leaves are sometimes consumed by livestock, but it seems that important differences exist in this respect between Indian and East African Neems on the one hand and West African Neems on the other. The former are more or less acceptable as browse, while the latter are not, even for camels. It has been suggested that livestock browse Neem from time to time as a cure for some diseases.

Main References:

Baumer, M. 1983. Notes on Trees and Shrubs in Arid and Semi-arid Regions. FAO/UNEP programme “Ecological Management of Arid and Semi-Arid Rangelands in Africa, Near and Middle East” (EMASAR Phase II). 270p.