Commercial Timbers


H. G. Richter and M. J. Dallwitz

Azadirachta spp. (Neem)

Nomenclature etc. MELIACEAE. Species included in the description: Azadarichta excelsa (Jack) Jacobs (2), Azadarichta indica A.H.L.Juss. (2). Not protected under CITES regulations.

Description based on 4 specimens. Tree. Geographic distribution: India, Pakistan, Sri Lanka, Burma, and Indomalesia.

General. Growth ring boundaries distinct. Growth ring boundaries in A.indica demarcated by marginal parenchyma bands. Heartwood basically brown and red, without streaks. Sapwood colour distinct from heartwood colour. Odour distinct. Density 0.55–0.85 g/cm³. A. indica: heartwood reddish brown; A. excelsa: heartwood brown.

Vessels. Vessels present. Wood diffuse-porous. Vessels arranged in no specific pattern, in multiples, commonly short (2–3 vessels) radial rows and in clusters. Vessel outline rounded. Two distinct vessel diameter classes absent. Average tangential vessel diameter 120–190–320 µm; diameter of vessel lumina: large and very large. Average number of vessels/mm² 3–5; vessels per square millimetre very few. Average vessel element length 120–450 µm. Average vessel element length short and medium. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 3–5 µm, small, not vestured. Vessel-ray pits with distinct borders, similar to intervessel pits, of uniform size or type, of the same type in adjacent elements, located throughout the ray. Helical thickenings absent. Tyloses in vessels absent. Other deposits in heartwood vessels present, brown deposits.

Tracheids and fibres. Vascular or vasicentric tracheids sporadic to absent. Fibres very thin-walled and of medium wall thickness. Average fibre length (250–)900(–1620) µm. Average fibre length medium. Fibre pits mainly restricted to radial walls, simple to minutely bordered. Helical thickenings absent. Fibres non-septate.

Axial parenchyma. Axial parenchyma present, banded. Axial parenchyma bands marginal (or seemingly marginal), bands much wider than rays, coarse, more than three cells wide, 2–3 per radial mm. Axial parenchyma apotracheal and paratracheal. Apotracheal axial parenchyma diffuse. Paratracheal axial parenchyma scanty and vasicentric. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 3–6. Unlignified parenchyma absent.

Rays. Rays present, 4–10 per tangential mm, multiseriate (also if only few), (1–)2–3(–4) cells wide, narrow (2–3 seriate). Rays with multiseriate portions as wide as uniseriate portions present and absent. Aggregate rays absent. Rays of one size. Height of large rays up to 500 µm. Rays composed of a single cell type (homocellular) and two or more cell types (heterocellular); homocellular ray cells procumbent. Heterocellular rays with square and upright cells restricted to marginal rows, mostly 1 marginal row of upright or square cells. Sheath cells absent. Tile cells absent. Perforated ray cells absent. Disjunctive ray parenchyma end walls indistinct or absent. Homocellular rays observed only in A. excelsa.

Storied structures. Storied structure absent.

Secretory structures. Oil and mucilage cells absent. Intercellular canals absent. Laticifers or tanniniferous tubes absent.

Cambial variants. Included phloem absent. Other cambial variants absent.

Mineral inclusions. Crystals present, prismatic, located in axial parenchyma cells. Crystal-containing axial parenchyma cells chambered. Number of crystals per cell or chamber one. Crystal containing cells of normal size. Cystoliths absent. Silica not observed.

Physical and chemical tests. Heartwood not fluorescent. Water extract fluorescent; basically colourless to brown or shade of brown and yellow or shade of yellow. Heartwood extractives not leachable by water. Ethanol extract fluorescent and not fluorescent. Colour of ethanol extract colourless to brown or shade of brown and yellow or shade of yellow. A.excelsa: water extract colourless to light brown, with yellow fluorescence; ethanol extract colourless to brown, not fluorescent. A.indica: water extract yellow, with greenish fluorescence; ethanol extract yellow, with greenish fluorescence. Chrome azurol-S test negative. Froth test positive and negative (A. excelsa negative; A. indica positive). Splinter burns to partial ash. Ash bright white.

Illustrations. • Transverse section. Azadirachta excelsa. • Tangential section. Azadirachta excelsa. • Radial section. Azadirachta excelsa.

The interactive key allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, summaries of attributes within groups of taxa, and geographical distribution.

Cite this publication as: ‘Richter, H.G., and Dallwitz, M.J. 2000 onwards. Commercial timbers: descriptions, illustrations, identification, and information retrieval. In English, French, German, Portuguese, and Spanish. Version: 25th June 2009.’.