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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 India and Burma, growing in tropical and semi-tropical regions. Other vernacular names include Margosa, Nimtree, Nimba, Vepu, Vempu, Veppam (Tamil language) 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.


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).
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.
But Neem is far more than a tough tree that grows vigorously in difficult sites. Among its many benefits, the one that is most unusual and immediately practical is the control of farm and household pests. Some entomologists now conclude that neem has such remarkable powers for controlling insects that it will usher in a new era in safe, natural pesticides.

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).

Cultivation and uses

Neem has been introduced into cultivation over wide areas of Asia, Africa, the Americas, Australia and the islands of the south Pacific. It is present mainly in the drier (arid) tropical and subtropical zones. Mountainous areas are generally avoided.
The beneficial properties of the neem tree have been part of Indian folklore for thousands of years. Dubbed 'the village pharmacy', it has numerous medicinal properties, aiding conditions ranging from digestive disorders to diabetes and from high cholesterol to cancer. To this day, neem twigs are used for brushing teeth in India (similar to the manner in which miswak sticks are used in the Middle East), perhaps one of the earliest and most effective forms of dental care. In some parts of Sub-Saharan Africa the bark is used as both toothbrush and toothpaste, and for treating malaria. For many of the medicinal properties mentioned, no scientific data exists, but the fame is based on traditional knowledge (Ayurvedic medicine) or anecdotal stories. All parts of the tree (seeds, leaves, flowers and bark) are used for preparing many different medical preparation and neem oil is also 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.

Uses in pest and disease control

Both polar extracts and neem oil are of primary interest to research scientists as an insecticide. The active insecticidal ingredient, azadirachtin, is also effective against mites and other arthropods. Many of the tree's secondary metabolites have biological activity, but azadirachtin is considered to be of the most ecological importance. Studies have shown a wide spectrum of activity and species affected. It acts by breaking the insect's lifecycle. Research has increased in the past few years as the desire for safer pest control methods increases and it becomes apparent that this tree will be able to play a role in integrated pest management systems. Because of its low toxicity [1], neem oil is available for general use in most countries, and is permitted for restricted use under the National Organic Program in the United States.
Other ingredients in neem oil are also effective as fungicides.
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 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 drink it.)

Culinary use

The tender shoots of the neem tree are eaten as a vegetable in India. In the state of Tamil Nadu in South India, a special dish called 'veppam poo rasam' is popular. The name 'veppam poo rasam' literally translates to neem flowers rasam. When the tree flowers, many of these flowers fall under the tree, which are collected and dried further to be used through the year. As the flowering usually coincides with the Tamil new year, the flowers are also used to make another dish called 'pacchadi' for the new year feast.
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). 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.

Patent controversy

In 1995 the European Patent Office (EPO) granted a patent on an anti-fungal product, derived from neem, to the United States Department of Agriculture and multinational WR Grace. The Indian government challenged the patent when it was granted, claiming that the process for which the patent had been granted had actually been in use in India for over 2000 years. In 2000 the EPO ruled in India's favour but the US multinational mounted an appeal claiming that prior art about the product had never been published in a scientific journal. On 8 March 2005, that appeal was lost and the EPO revoked the neem patent. Other aspects of neem use continue to be patented, not least in India itself. The US Patent Office has published over 60 patents since 1975 that refer to neem.

Neem cake

Neem cake organic manure is the by-product obtained in the process of cold pressing of Neem fruits and kernels, and the solvent extraction process for neem oil cake. It is a potential source of organic manure under the Bureau of India Standards, Specification No. 8558. Neem has demonstrated considerable potential as a fertilizer. For this purpose, neem cake and neem leaves are especially promising.

Components

Neem cake organic manure has more nitrogen (2-3%), phosphorus (1%), potassium (1.4%), calcium and magnesium compared to farmyard manure. It is rich in both sulphur compounds and bitter limonoids.
According to research calculations, neem cake seems to make soil more fertile due to an ingredient that blocks soil bacteria from converting nitrogenous compounds into nitrogen gas. It is a nitrification inhibitor and prolongs the availability of nitrogen to both short duration and long duration crops.

Use as a Fertilizer

Neem cake organic manure protects plant roots from nematodes, soil grubs and white ants probably due to its content of the residual limonoids. It also acts as a natural fertilizer with pesticidal properties. Neem cake is widely used in India to fertilize paddy, cotton and sugarcane. Usage of neem cake have shown an increase in the dry matter in Tectona grandis (Teak), Acacia nilotica (Gum Arabic), and other forest trees.

Pest Control

Neem cake is effective in the management of insects and pests. The bitter principles of the soil and cake have been reported to have seven types of activities (a) antifeedant (b) attractant (c)repellent (d) insecticide (e) nematicide (f) growth disruptor and (g) antimicrobial.
The cake contains salannin, nimbin, azadirachtin and azadiradione as the major components. Of these, azadirachtin and meliantriol are used as locust antifeedants while salannin is used as an antifeedant for the housefly.

Neem oil

Neem oil is a vegetable oil pressed from the fruits and seeds of Neem (Azadirachta indica), an evergreen tree which is endemic to the Indian sub-continent and has been introduced to many other areas in the tropics. It is perhaps the most important of the commercially available products of neem. Characteristics

Neem oil is generally light to dark brown, bitter and has a rather strong odour that is said to combine the odours of peanut and garlic. It comprises mainly triglycerides and large amounts of triterpenoid compounds, which are responsible for the bitter taste. It is hydrophobic in nature and in order to emulisify it in water for application purposes, it must be formulated with appropriate surfactants.
Neem oil also contains steroids (campesterol, beta-sitosterol, stigmasterol) and a plethora of triterpenoids of which Azadirachtin is the most well known and studied. The Azadirachtin content of Neem Oil varies from 300ppm to over 2000ppm depending on the quality of the neem seeds crushed.
Average composition of Neem Oil fatty acids
Common Name
Acid Name
Composition range
Omega-6
Linoleic acid
6-16%
Omega-9
Oleic acid
25-54%
Palmitic acid
Hexadecanoic acid
16-33%
Stearic acid
Octadecanoic acid
9-24%
Omega-3
Alpha-linolenic acid
?%
Palmitoleic acid
9-Hexadecenoic acid
?%

Methods of extraction

The method of processing is likely to affect the composition of the oil, since the methods used, such as pressing (expelling) or solvent extraction are unlikely to remove exactly the same mix of components in the same proportions.The Neem oil yield that can be obtained from neem seed kernels varies also widely in literature and varies from 25% to 45%.
The oil can be obtained through pressing (crushing) of the seed kernel both through cold pressing or through a process incorporating temperature controls.
Neem seed oil can also be obtained by solvent extraction of the neem seed, fruit, oilcake or kernel. A large industry in India extracts the oil remaining in the seed cake using hexane. This solvent-extracted oil is of a lower quality as compared to the cold pressed oil and is mostly used for soap manufacturing. Neem cake is a by-product obtained in the solvent extraction process for neem oil.

Uses

Neem oil is not used for cooking purposes but, in India and Bangladesh, it is used for preparing cosmetics (soap, hair products, body hygiene creams, hand creams) and in Ayurvedic, Unani and folklore traditional medicine, in the treatment of a wide range of afflictions. The most frequently reported indications in ancient Ayurvedic writings are skin diseases, inflammations and fevers, and more recently rheumatic disorders, insect repellent and insecticide effects.
Traditional Ayurvedic uses of neem include the treatment of fever, leprosy, malaria, ophthalmia and tuberculosis. Various folk remedies for neem include use as an anthelmintic, antifeedant, antiseptic, diuretic, emmenagogue, contraceptive, febrifuge, parasiticide, pediculocide and insecticide. It has been used in traditional medicine for the treatment of tetanus, urticaria, eczema, scrofula and erysipelas. Traditional routes of administration of neem extracts included oral, vaginal and topical use. Neem oil has an extensive history of human use in India and surrounding regions for a variety of therapeutic purposes.
Formulations made of Neem oil also find wide usage as a bio-pesticide for organic farming, as it repels a wide variety of pests including the mealy bug, beet armyworm, aphids, the cabbage worm, nematodes and the Japanese beetle. Neem Oil is non-toxic to mammals and birds as well as many beneficial insects such as honeybees and lady bugs. Neem oil also controls black spot, powdery mildew, anthracnose and rust (fungus).
For use as a bio-pesticide, pure Neem oil should be diluted at the rate of 1 teaspoon per quart or 4 teaspoons per gallon of water. Adding a surfactant greatly enhances its effectiveness. It can also be used as a cure for Static Lice in Cavies (Guinea Pigs).