Neem

An evergreen tree up to 15–20 m tall with a dense rounded crown; the grey-brown bark is fissured and reddish inside. The twice-pinnate leaves have 20–31 lanceolate, finely serrate leaflets arranged alternately. The small, cream-white, fragrant flowers are rich in nectar, borne in axillary panicles in spring–summer. The fruit is an ellipsoid drupe 1.4–2.8 cm long, pale green turning yellow when ripe, bitter, holding a single seed within a thin coat. Neem tolerates drought very well, grows fast on poor soils and has a deep root system.

Neem is native to the Indian subcontinent and has been cultivated for over 2,000 years; today it has been widely introduced across the tropics: Southeast Asia, Africa (the Sahel), tropical America and Oceania. Every part of the tree contains limonoids such as azadirachtin and nimbin: leaves, bark and roots are used in traditional medicine (fever, adjunct therapy for diabetes, skin ailments, oral hygiene — twigs are chewed as toothbrushes); the seeds are pressed for neem oil used in cosmetics, soap and insect repellents; the seed cake rich in azadirachtin is used for biopesticides and organic fertiliser. In Vietnam, neem is planted as a shade tree and coastal shelterbelt against drifting sand in arid provinces such as Ninh Thuận and Bình Thuận, and for soil improvement.