Commercial Timbers


H. G. Richter and M. J. Dallwitz

Acer spp. (Ahorn, maple)

Nomenclature etc. ACERACEAE. + Acer pseudoplatanus L., A. saccharum L., Acer platanoides L., A. campestre L. Trade and local names: Ahorn (DE); sycamore (GB); maple (US); érable (FR); acero (IT); falso plátano (ES). Not protected under CITES regulations.

Tree. Geographic distribution: Europe, excl. Mediterranean, Mediterranean incl. N. Africa and Middle East, temperate Asia, and North America.

General. Growth ring boundaries distinct. Heartwood basically white or grey brown to white or grey brown to yellow white or grey to red (generally white to yellowish). Sapwood colour similar to heartwood colour (occasionally dark coloured heartwood present). Density 0.5–0.6–0.7 g/cm³ (US: up to 0.56 = "soft maple", up to 0.80 = "hard maple"; A. pseudoplatanus around 0.60). Wood surface darkens considerably under exposure; special growth patterns: "fiddle back" figure in all species, "bird's eye" figure only in A. saccharum.

Vessels. Wood diffuse-porous. Vessels in multiples, commonly short (2–3 vessels) radial rows. Occasionally small clusters and radial groups of 4. Average tangential vessel diameter 44–65–80 µm. Average number of vessels/mm² 34–38–44. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 8–10 µm. Vessel-ray pits with reduced borders or apparently simple, rounded or angular, of uniform size or type, of the same type in adjacent elements. Helical thickenings present, in narrow and wide vessel elements, throughout the body of vessel elements. Tyloses in vessels absent. Other deposits in heartwood vessels not observed.

Tracheids and fibres. Fibres of medium wall thickness. Average fibre length 670–880–1080 µm. Fibre pits mainly restricted to radial walls, simple to minutely bordered. Fibres adjacent to vessels with thicker walls.

Axial parenchyma. Axial parenchyma banded. Axial parenchyma bands marginal (or seemingly marginal), fine, up to three cells wide. Axial parenchyma apotracheal and paratracheal. Apotracheal axial parenchyma diffuse. Paratracheal axial parenchyma scanty. Axial parenchyma fusiform and as strands. Average number of cells per axial parenchyma strand 2(–4).

Rays. Rays 6–9–14 per tangential mm, multiseriate (also if only few), 1–6(–8) cells wide. Rays of two distinct sizes (1–2-seriate and 5–7-seriate), or of one size (in some species). Rays composed of a single cell type (homocellular); homocellular ray cells procumbent. There is no safe way of differentiating the various species based on microscopic features; within the European species only A. campestre may be separated from other species on account of the fairly narrow rays.

Storied structures. Storied structure absent.

Mineral inclusions. Crystals mostly present, prismatic, located in axial parenchyma cells. Crystal-containing axial parenchyma cells chambered. Number of crystals per cell or chamber one. Crystals observed in many species, i.e., A. campestre and A. rubrum; in some species not, i.e., A. pseudoplatanus. Silica not observed.

Illustrations. • Macro images. Transverse. Radial. Acer pseudoplatanus. • Transverse section. Acer platanoides. Acer campestre. • Transverse section. Acer saccharum. • Transverse section. Acer pennsylvanicum (higher magnification). • Tangential section. Acer platanoides. Inset: Helical thickenings in vessels. • Radial section. Acer platanoides. Inset: Homocellular rays, cross-field pits similar to intervascular pits in size and form but with reduced borders ("simple" pits).

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.’.