Neem | Archives | Aggie Horticulture

1. Q. What is neem? Where does it come from?

A. Neem is the "Chinaberry's Miraculous Cousin".

Most local folks are familiar with the abundant Chinaberry tree, Melia azedarach. Also known as umbrella tree, this naturalized western Asian tree is a colonizer of disturbed sites throughout the South. It has its faults including surface roots, brittle wood, and messy, toxic berries. However, its ability to grow in hostile sites and produce dense shade has endeared it to man and beast alike.

In the seasonally dry hills of central India, the Chinaberry's cousin, Azadirachta indica, leads a communal existence with the people and animals in villages and along roadsides. As much of this land was long ago deforested as a result of population pressures, the presence of these trees reflects the Indians' obvious appreciation of the cooling shade they provide. The common name of this tree in India is "neem", and shade is not the only reason to grow it.

The neem is known to Indians as a virtual living pharmacy. Daily, millions of people brush their teeth with neem twigs. Dentists confirm that this practice guards against periodontal disease. A crude antiseptic soap is made from the pulp of the olive-like fruit. A paste made from the leaves has been found to successfully treat skin lesions. Small portions of leavers mixed with regular feed seem to affect intestinal parasites in livestock.

It was not until the 1920's that formal research was begun on neem trees. It was noted that during periodic locust plagues, while acres of foliage were stripped bare, neem were left unscathed. Simply derived "tea" solutions made from the neem seed were effective in protecting foliage crops. Additionally, several compounds were isolated from the seeds of neem. One of these, azadirachtin, was found to both repel and disrupt the growth and reproduction of many destructive insect species. Unlike many synthetic insecticides, low dozes of azadirachtin were found to have little or no mammalian toxicity, and insects showed little resistance to the compound even through several generations. The range of insects affected by neem extracts is impressive and includes beetles, flies, mosquitoes, caterpillars, true bugs, locusts and grasshoppers, aphids, weevils, moths, and roaches. The zoo is currently experimenting with a commercial insecticide containing azadarachtin.

The major by-product from processing neem is called "cake." Fields top-dressed with cake were found to be less affected by nematodes, snails, and certain fungi. Later tests showed neem oil to be very effective on plant diseases like rust and powdery mildew. Neem cake was also found to be excellent fertilizer, outperforming farm manure and sewage sludge.

Neem trees are easily grown in warm, frost-free areas and are relatively fast-growing. In many areas of Third World countries, wood of any kind is at a premium. Neem timber has been shown to be rot and insect-resistant.

Neem oil is clean-burning, and the tree produces excellent firewood. Resin produces excellent firewood. Resin tapped from the bark provides a gum commonly used as a glue.

Perhaps the most important trait of neem is its ability to persist and grow in drought-prone soils. Many areas of Africa have suffered from overgrazing and subsequent desertification. The Sahara Desert has advanced relentlessly, aided by the ever- increasing population demands along its borders, especially in the Sahel, an area south of the desert which covers six countries from Senegal to Chad. Re-forestation efforts have been greatly aided by the introduction of neem trees to these areas. Other countries successfully growing neem include Cambodia, Indonesia, Iran, Nepal, Pakistan, Thailand, Vietnam, Saudi Arabia, China, Haiti, Dominican Republic, Nicaragua, Mexico, Guatemala, and Honduras. A few trees currently exist in southern Florida, Hawaii, Texas and Puerto Rico.

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