Commercial Timbers


H. G. Richter and M. J. Dallwitz

Paulownia tomentosa (Thunb. ex Murr) Steud. (Kiri)

Nomenclature etc. SCROPHULAIDACEAE. Syn.: Paulownia imperialis Sieb. & Zucc. Trade and local names: kiri, shima-giri (JP); Paulownia (trade). Not protected under CITES regulations.

Tree. Geographic distribution: temperate Asia (cultivated worldwide in temperate and subtropical climate regions).

General. Growth ring boundaries distinct. Heartwood basically white or grey, without streaks. Sapwood colour similar to heartwood colour. Odour indistinct or absent. Density 0.25–0.3 g/cm³.

Vessels. Vessels present. Wood ring-porous or semi-ring-porous. Vessels arranged in no specific pattern, in multiples, commonly short (2–3 vessels) radial rows. Vessel outline angular. Average tangential vessel diameter 200–300 µm (earlywood); diameter of vessel lumina: large to very large. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 6–8 µm, small to medium. Vessel-ray pits with distinct borders or with reduced borders or apparently simple, similar to intervessel pits, rounded or angular. Helical thickenings present, only in narrow vessel elements, throughout the body of vessel elements. Tyloses in vessels present, thinwalled.

Tracheids and fibres. Fibres very thin-walled. Fibre pits mainly restricted to radial walls, simple to minutely bordered. Fibres non-septate.

Axial parenchyma. Axial parenchyma banded or not banded. Axial parenchyma bands marginal (or seemingly marginal), bands much wider than rays, coarse, more than three cells wide (intial parenchyma as wide as the earlywood pore ring). Axial parenchyma paratracheal. Paratracheal axial parenchyma vasicentric, or aliform, or confluent (latewood vessles only). Aliform parenchyma lozenge and winged. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 2–5.

Rays. Rays 3–6 per tangential mm, multiseriate (also if only few), 2–5 cells wide, narrow (2–3 seriate) to of medium width (3–5 seriate). Height of large rays up to 500 µm. Rays composed of a single cell type (homocellular), or 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.

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 not observed. Silica not observed.

Physical and chemical tests. Heartwood not fluorescent.

Illustrations. • Transverse section. Paulownia tomentosa. • Tangential section. Paulownia tomentosa. • Radial section. Paulownia tomentosa.

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.’.