Tree to 10 m. Bark smooth, grey to grey-brown. Branchlets green in first season, becoming grey-brown with yellow pubescence. Buds with two glabrous, ribbed scales. Leaves deciduous, 6–16 × 2.5–7 cm, obovate to oblong, upper surface glabrous, lower surface glandular, glabrous, but for dense pubescence in the axils of the lateral veins, 6–13 lateral veins on each side of the midvein, margins with minute serrations, apex acute, acuminate or caudate; petiole largely glabrous, 0.5–3 cm long. Staminate inflorescences catkin-like, 3–4 cm long; pistillate inflorescences in racemes of two to four, pedunculate, oblong, 1–2.5 × 1–1.5 cm. Cone woody, 1.8–2 × 0.7–1 cm, bracts 0.5–0.7 cm wide. Flowering May to June, fruiting July to August (China). Li & Skvortsov 1999. Distribution CHINA: Anhui, Fujian, northern Guangdong, Guizhou, southern Henan, Hubei, eastern Hunan, Jiangsu, Jiangxi, Zhejiang; JAPAN: Honshu. Habitat Riverbanks in montane forest, between 200 and 1000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT145.
Alnus trabeculosa is rare in cultivation although widely distributed as a wild plant. There are scattered trees in collections across Europe: for example, there is one at the National Botanical Garden of Belgium, Meise, originating from the Hangzhou Botanical Garden, accessioned in 1991, and it also grows at the Botanischer Garten Berlin-Dahlem, and Freiburg-Günterstal Arboretum in Germany. In the United Kingdom it seems to be known only from an introduction in early 1997 of seeds given to Ray Townsend and Mark Bridger at the Forest Tree Breeding Centre at Juo Town in Ibaraki Prefecture, Honshu. Our illustration (Figure 15) was drawn from one of the resulting trees at Kew, now 1.6 m tall, though with a broken leader. At Howick it has also been slow, one specimen there being less than 2 m tall when seen in 2005. The leaves are an attractive mid-green, and when young the midrib and principal veins are red.