Azadirachta indica

Neem (Azadirachta indica, syn. Melia azadirachta L., Antelaea azadirachta (L.) Adelb.) is a tree in the mahogany family Meliaceae. It is one of two species in the genus Azadirachta, and is native to Burma,India and Pakistan, growing in tropical and semi-tropical regions. Other vernacular names include Azad Dirakht (Persian), Margosa, Neeb (Arabic), Nimtree, Nimba (Sanskrit), Vepu, Vempu, Vepa (Telugu), Bevu in Kannada, Veppam in (Tamil) and Indian-lilac.

Neem is a fast growing tree that can reach a height of 15-20 m, rarely to 35-40 m. It is evergreen but under 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.

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The trunk is relatively short, straight and may reach a diameter of 1.2 m. The bark is hard, fissured or scaly, and whitish-grey to reddish-brown. The sapwood is greyish-white and the heartwood reddish when first exposed to the air becoming reddish-brown after exposure. The root system consists of a strong taproot and well developed lateral roots.

The alternate, pinnate leaves are 20-40 cm long, with 20-31 medium to dark green leaflets about 3-8 cm long. The terminal leaflet is often missing. The petioles are short. Very young leaves are reddish to purplish in colour. The shape of mature leaflets is more or less asymmetric and their margins are dentate with the exception of the base of their basiscopal half, which is normally very strongly reduced and cuneate.

The flowers (white and fragrant) are arranged axillary, normally more-or-less drooping panicles which are up to 25 cm long. The inflorescences, which branch up to the third degree, bear 150-250 flowers. An individual flower is 5-6 mm long and 8-11 mm wide. Protandrous, bisexual flowers and male flowers exist on the same individual (polygamous).

A Neem Blossom at Guntur, India

The fruit is a glabrous olive-like drupe which varies in shape from elongate oval to nearly roundish, and when ripe are 1.4-2.8 x 1.0-1.5 cm. The fruit skin (exocarp) is thin and the bitter-sweet pulp (mesocarp) is yellowish-white and very fibrous. The mesocarp is 0.3-0.5 cm thick. The white, hard inner shell (endocarp) of the fruit encloses one, rarely two or three, elongated seeds (kernels) having a brown seed coat.

Commercial plantations of the trees are not considered profitable. Around 50,000 neem trees have been planted near Mecca to provide shelter for the pilgrims.

Warning: The neem tree is very much lookalike to the Chinaberry, whose fruits (and everything else) are extremely poisonous.

• Close up photograph of neem seeds

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Neem flowers in closeup

Ecology

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. It can grow in regions with an annual rainfall below 400 mm, but in such cases it depends largely on the ground water levels. Neem can grow in many different types of soil, but it thrives best on well drained deep and sandy soils (pH 6.2-7.0). It is a typical tropical/subtropical tree and exists at annual mean temperatures between 21-32 °C. It can tolerate high to very high temperatures. It does not tolerate temperature below 4 °C (leaf shedding and death may ensue).

Chemical compounds

The active principles of the plant were brought to the attention of natural products scientists in 1942 when Salimuzzaman Siddiqui, while working at the Scientific and Industrial Research Laboratory at Delhi University, for the first time extracted three bitter compounds from neem oil, which he provisionally named as nimbin, nimbinin, and nimbidin respectively.

Usage

In India, the tree is variously known as 'Divine Tree',"Heal All","Nature's Drugstore", "Village Pharmacy" and "Panacea for all diseases". Products made from neem have proven medicinal properties as: antihelmintic, antifungal, antidiabetic, antibacterial, antiviral,and antifertility etc. It is particularly prescribed for skin disease (Puri,1999).

• Neem twigs are used for brushing teeth in India and Pakistan. This practice is perhaps one of the earliest and most effective forms of dental care.
• All parts of the tree (seeds, leaves, flowers and bark) are used for preparing many different medical preparation.
• Neem oil is used for preparing cosmetics (soap, shampoo, balms and creams).
• Besides its use in traditional Indian medicine the neem tree is of great importance for its anti-desertification properties and possibly as a good carbon dioxide sink.
• Neem oil is useful for skin care such as acne, and keeping skin elasticity.
• Practictioners of traditional Indian medicine recommend that patients suffering from Chicken Pox sleep on neem leaves.

Horticultural usages

Neem is a source of environment-friendly biopesticides. Among the isolated neem constituents, liminoids (such as Azadirachtin) are effective in insect growth-regulating activity. The unique feature of neem products is that they do not directly kill the pests, but alter the life-processing behavior in such a manner that the insect can no longer feed, breed or undergo metamorphosis. However, this does not mean that the plant extracts are harmful to all insects. Since, to be effective, the product has to be ingested, only the insects that feed on plant tissues succumb. Those that feed on nectar or other insects (such as spiders, butterflies, bees, and ladybugs) hardly accumulate significant concentrations of neem products.

Uses in pest and disease control

Neem is deemed very effective in the treatment of scabies although only preliminary scientific proof exists which still has to be corroborated, and is recommended for those who are sensitive to permethrin, a known insecticide which might be an irritant. Also, the scabies mite has yet to become resistant to neem, so in persistent cases neem has been shown to be very effective. There is also anecdotal evidence of its effectiveness in treating infestations of head lice in humans. It is also very good for treating worms (soak the branches and leaves in lukewarm water and then drink it).

Culinary use

The tender shoots and flowers of the neem tree are eaten as a vegetable in India. Neem flowers are very popular for their use in Ugadi Pachadi(soup like pickle)^recipe which is made on Ugadi day in South India.

Neem is also used in parts of mainland Southeast Asia, particularly in Cambodia (where it is known as sadao or sdao), Laos (where it is called kadao) and Vietnam (where it is called sầu đâu).^recipe Even lightly cooked, the flavour is quite bitter and thus the food is not enjoyed by all inhabitants of these nations, though it is believed to be good for one's health.