Commercial Timbers


H. G. Richter and M. J. Dallwitz

Betula spp. (Birke, birch)

Nomenclature etc. BETULACEAE. B. verrucosa = B. pendula. Trade and local names: commercially three types of birch timbers are distinguished: "heavy" includes B. alleghaniensis - yellow birch (US, CA); B. lenta - sweet birch, black birch (US, CA); B. schmidtii - Japanese hard birch (onoore); "moderately heavy": B. maximowicziana - Eastasian birch (saibada) and European species such as B. pubescens, B. verrucosa - European birch, common birch (GB), berken (NL), bouleau (FR), abedul (ES); "light": B. papyrifera - paper birch (US, CA); B. populifera - gray birch, wire birch (US, CA); B. alnoides - Indian birch (layang). Not protected under CITES regulations.

Tree. Geographic distribution: Europe, excl. Mediterranean, North America, temperate Asia, and India, Pakistan, Sri Lanka.

General. Growth ring boundaries distinct. Heartwood basically yellow to white or grey to red brown (heavier timbers yellowish brown to red brown). Sapwood colour similar to heartwood colour. Density 0.46–0.61–0.8 g/cm³ (average density "heavy": 0.70, "moderately heavy": 0.60, "light": 0.55).

Vessels. Vessels present. Wood diffuse-porous. Vessels in multiples, commonly short (2–3 vessels) radial rows (occasionally also in radial chains of 4–6). Average tangential vessel diameter 30–90–130 µm. Average number of vessels/mm² 40–60. Perforation plates scalariform, with (6–)10–20(–25) bars. Intervessel pits alternate, average diameter (vertical) 3–4 µm. Vessel-ray pits with distinct borders, similar to intervessel pits. Helical thickenings absent.

Tracheids and fibres. Fibres of medium wall thickness. Average fibre length 300–1000–1700 µm. Fibre pits mainly restricted to radial walls, distinctly bordered. Fibres non-septate.

Axial parenchyma. Axial parenchyma banded. Axial parenchyma bands marginal (or seemingly marginal), fine, up to three cells wide. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 6–8–10.

Rays. Rays 10–17–20 per tangential mm, multiseriate (also if only few), 1–4 cells wide. Rays composed of a single cell type (homocellular); homocellular ray cells procumbent.

Mineral inclusions. Crystals not observed. Silica not observed.

Illustrations. • Macro images. Transverse. Transverse. Betula sp. • Transverse section. Betula pendula. • Tangential section. Betula pendula. • Radial section. Betula pendula. • Miscellaneous. Betula pendula. Note: scalariform perforation plates and minute intervessel as well as vessel-ray pitting.

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.’.