Neem (Azadirachta indica) is a tree in the mahogany family Meliaceae. It is one of two species in the genus Azadirachta, and is native to India, Myanmar, Bangladesh, Sri Lanka, Malaysia and Pakistan, growing in tropical and semi-tropical regions. Other vernacular names include Neem (Hindi, Urdu and Bengali), Nimm (Punjabi), Arya Veppu (Malayalam), Neem in Bengali, Azad Dirakht (Persian), Nimba (Sanskrit and Marathi), DogonYaro (in some Nigerian languages), Margosa, Neeb (Arabic), Nimtree, Vepu, Vempu, Vepa (Telugu), Bevu (Kannada), Kohomba (Sinhala), Vempu (Tamil), Tamar (Burmese), and Indian Lilac (English). In East Africa it is also known as Muarubaini (Swahili), which means the tree of the 40, as it is said to treat 40 different diseases.
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 trunk is relatively short, straight and may reach a diameter of 1.2 m (about 4 feet).
The opposite, pinnate leaves are 20-40 cm (8 to 16 in.) long, with 20 to 31 medium to dark green leaflets about 3-8 cm (1 to 3 in.) long.
The (white and fragrant) flowers are arranged axillary, normally in more-or-less drooping panicles which are up to 25 cm (10 in.) long. The inflorescences, which branch up to the third degree, bear from 150 to 250 flowers. An individual flower is 5-6 mm long and 8-11 mm wide.
The fruit is a smooth (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.
The neem tree is very similar in appearance to the Chinaberry, all parts of which are extremely poisonous.
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 ground water levels. 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 . Neem is a life-giving tree, especially for the dry coastal, southern districts. It is one of the very few shade-giving trees that thrive in the drought-prone areas. The trees are not at all delicate about the water quality and thrive on the merest trickle of water, whatever the quality. In Tamil Nadu it is very common to see neem trees used for shade lining the streets or in most people's back yards. In very dry areas, like Sivakasi, the trees are planted in large tracts of land, in whose shade fireworks factories function.
Neem is considered an invasive species in many areas where it is non-native.
 Chemical Compounds
The (subsequently) Pakistani scientist Salimuzzaman Siddiqui was the first scientist to bring the plant to the attention of phytopharmacologists. In 1942 (Pakistan was separated from India in 1947) while working at the Scientific and Industrial Research Laboratory at Delhi University, India, he extracted three bitter compounds from neem oil, which he named nimbin, nimbinin, and nimbidin respectively. The seeds contain a complex secondary metabolite azadirachtin.
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, being anthelmintic, antifungal, antidiabetic, antibacterial, antiviral, anti-fertility, and sedative. It is considered a major component in Ayurvedic medicine and is particularly prescribed for skin disease.
Extract of neem leaves is thought to be helpful as malaria prophylaxis despite the fact that no comprehensive clinical studies are yet available. In several cases, private initiatives in Senegal were successful in preventing malaria . However, major NGOs such as USAID are not supposed to use neem tree extracts unless the medical benefit has been proved with clinical studies.
 Uses in pest and disease control
Neem is deemed very effective in the treatment of scabies, although only preliminary scientific proof, which still has to be corroborated, exists, 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. A tea made of boiled neem leaves, sometimes combined with other herbs such as ginger, can be ingested to fight intestinal worms.
The oil is also used in sprays against fleas for cats and dogs.
 Hindu tradition and neem leaves
In Hindu tradition the amman festivals falls in summer season in the southern states of Andhrapradesh and Tamilnadu. There is a good reason for the festival being celebrated in the summer months (during summer season) because certain heat-related diseases such as measles, small pox, chicken pox, prickly heat disorders, and sweat rash are considered to spread faster and be more common then. In order to avoid these infectious and non-infectious diseases, people started celebrating this festival using neem leaves and neem bark. People unaware of the fact that neem leaves have antiseptic, anti-bacterial, and anti-fungal properties, believe that it is a gift from god and so they gracefully worship god using Neem leaves and turmeric powder.
It is also believed that sleeping on a layer of Neem leaves is a effective cure for chicken pox and measles; the leaves are also gently rubbed over the body in an attempt to ensure a quick recovery. This traditional treatment is still used in many rural areas of India, north and east parts of Sri Lanka.
 As a vegetable
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 Pachhadi (soup-like pickle), which is made on Ugadi day in the South Indian States of Andhra Pradesh, Tamilnadu and Karnataka. A souplike dish called Veppampoo Rasam (Tamil) (translated as "neem flower rasam") made of the flower of neem is prepared in Tamil Nadu.
Neem is also used in parts of mainland Southeast Asia, particularly in Cambodia, Laos (where it is called kadao), Thailand (where it is known as sadao or sdao), Myanmar (where it is known as tamar) and Vietnam (where it is known as sầu đâu and is used to cook the salad: gỏi 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. Neem Gum is a rich source of protein. In Myanmar, young neem leaves and flower buds are boiled with tamarind fruit to soften its bitterness and eaten as a vegetable. Pickled neem leaves are also eaten with tomato and fish paste sauce in Myanmar.
 Association with Hindu festivals in India
Neem leaf or bark is considered an effective pitta pacifier due to its bitter taste. Hence, it is traditionally recommended during early summer in Ayurveda (that is, the month of Chaitra as per the Hindu Calendar which usually falls in the month of March - April), and during Gudi Padva, which is the New Year in the state of Maharashtra, the ancient practice of drinking a small quantity of neem juice or paste on that day, before starting festivities, is found. As in many Hindu festivals and their association with some food to avoid negative side-effects of the season or change of seasons, neem juice is associated with Gudi Padva to remind people to use it during that particular month or season to pacify summer pitta. In Tamilnadu during the summer months of April to June, the Mariamman temple festival is a thousand year old tradition. The Neem leaves and flowers are the most important part of the Mariamman festival. The goddess Mariamman statue will be garlanded with Neem leaves and flowers. During most occasions of celebrations and weddings the people of Tamilnadu adorn their surroundings with the Neem leaves and flowers as a form of decoration and also to ward off evil spirits and infections.
 Patent Controversy
In 1995 the European Patent Office (EPO) granted a patent on an anti-fungal product, derived from neem, to the US Department of Agriculture and multinational W. R. Grace and Company. 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 rights keeping the tree free of these patent restrictions.
 See Also