Azadirachta indica, commonly known as margosa, neem, nimtree or Indian lilac, is a tree in the mahogany family Meliaceae. It is one of two species in the genus Azadirachta. It is native to the Indian subcontinent and to parts of Southeast Asia, but is naturalized and grown around the world in tropical and subtropical areas. Its fruits and seeds are the source of neem oil. Nīm () is a Hindustani noun derived from Sanskrit nimba ().
Description
Margosa is a fast-growing tree that can reach a height of , and rarely . It is evergreen, shedding many of its leaves during the dry winter months. The branches are wide and spreading. The fairly dense crown is roundish and may reach a diameter of . The opposite, pinnate leaves are long, with 20 to 30 medium to dark green leaflets about long. The terminal leaflet often is missing. The petioles are short.
White and fragrant flowers are arranged in more-or-less drooping axillary panicles which are up to long. The inflorescences, which branch up to the third degree, bear from 250 to 300 flowers. An individual flower is long and wide. Protandrous, bisexual flowers and male flowers exist on the same individual tree.
The fruit is a smooth (glabrous), olive-like drupe which varies in shape from elongate oval to nearly roundish, and when ripe is by . The fruit skin (exocarp) is thin and the bitter-sweet pulp (mesocarp) is yellowish-white and very fibrous. The mesocarp is 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 margosa tree is similar in appearance to its relative, the chinaberry or bakain, Melia azedarach, with which it may be confused. Melia azedarach also has toothed leaflets and similar looking fruit. One difference is that margosa leaves are pinnate but chinaberry leaves are twice- and thrice-pinnate.
Taxonomy
The name Azadirachta indica was first published by Adrien-Henri de Jussieu in 1830. In 1753, Carl Linnaeus had described two species, Melia azedarach and Melia azadirachta. De Jussieu considered Melia azadirachta to be sufficiently different from Melia azedarach to be placed in a new genus. For both his species, Linnaeus referred to the name 'azedarach', which is derived from the French 'azédarac', which in turn is from the Persian 'āzād dirakht' (ازادرخت), meaning 'free or noble tree'. The Persian name of the tree, azad darakhat-e-hind, meaning 'the free tree of India, implies that it is free from disease and insect problems.
DistributionAzadirachta indica is considered to be native to the Indian region and Bangladesh in the Indian subcontinent and to Cambodia, Laos, Myanmar, Thailand and Vietnam in Indochina. It has been widely introduced elsewhere in tropical and subtropical regions, from South America to Indonesia.
Ecology
The margosa tree is noted for its drought resistance. Normally it thrives in areas with sub-arid to sub-humid conditions, with an annual rainfall of . It can grow in regions with an annual rainfall below 400 mm, but in such cases it depends largely on ground water levels. Margosa 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 of . It can tolerate high to very high temperatures and does not tolerate temperature below . Margosa is one of a very few shade-giving trees that thrive in drought-prone areas e.g. the dry coastal, southern districts of India and Pakistan. The trees are not at all delicate about water quality and thrive on the merest trickle of water, whatever the quality. In India and tropical countries where the Indian diaspora has reached, it is very common to see margosa trees used for shade lining streets, around temples, schools and other such public buildings or in most people's back yards. In very dry areas the trees are planted on large tracts of land.
Weed status
Margosa is considered as a weed in many areas, including some parts of the Middle East, most of Sub-Saharan Africa including West Africa and Indian Ocean states, and some parts of Australia. Ecologically, it survives well in similar environments to its own, but its weed potential has not been fully assessed.
In April 2015, A. indica was declared a class B and C weed in the Northern Territory, Australia, meaning its growth and spread must be controlled and plants or propagules are not allowed to be brought into the NT. It is illegal to buy, sell, or transport the plants or seeds. Its declaration as a weed came in response to its invasion of waterways in the "Top End" of the territory.