There are no active references in this article.
Tree 16–20(–30) m. Branchlets pubescent, green when young. Stipules large and conspicuous, especially on vigorous new shoots, 2–3 × 1–2 cm, elliptic to obovate. Leaves alternate, 10–17 × 9–13 cm, broadly ovate, sometimes weakly three-lobed, apex acuminate, base broadly cuneate, margins entire, slightly glossy dark green, tomentose when young, more or less glabrous when mature; petiole 3–6 cm, longer on young shoots. Inflorescences capitate on short peduncles or occasionally racemose, two to five in leaf axils, each with 8–13 flowers. Flowers hermaphrodite or female. Hermaphrodite flowers have no sepals but five linear petals, 2–3 mm long, and 10–15 stamens, 5 mm long: these form an inflorescence looking like a mass of stamens, although styles are also present. Female flowers have no sepals and no petals, so are composed only of three yellow-brown styles and gynoecia surrounded by a ring of lobules. Capsules ellipsoid, 7–9 × 5–6 mm, smooth, dehiscing above middle. Seeds narrowly winged. Flowering May to July, fruiting August to October (China). Kaul & Kapil 1974, Zhang et al. 2003b. Distribution BHUTAN; CHINA: Guangxi, Guizhou, Xizang, Yunnan; INDIA; INDONESIA; MALAYSIA; MYANMAR; NEPAL; SIKKIM; THAILAND; VIETNAM. Habitat Slopes in evergreen forests, c.1200(–2500) m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated (IUCN). The white, soft but durable timber is used in India, and the tree is also planted for afforestation in Sumatra. Illustration NT366, NT367.
Described as ‘a large poplar on steroids’ when mature (Hudson 2004), Exbucklandia populnea is a most distinctive and interesting tree, although in cultivation no specimens have yet reached the stature of even a small poplar. The first introductions to the West, by George Forrest, did not become established (Hudson 2004), the current stock having been introduced in more recent years. An early collection is represented by a specimen at the University of California Botanical Garden at Berkeley, derived from a gathering by B. Bartholomew in Bhutan in 1974. This is approximately 7.5 m tall with a spread of 4.5 m (Hogan 2008). Since then the species has achieved a reasonable distribution in milder gardens in the United States, where it is commercially available – although in the absence of fresh seed it is very difficult to propagate, as cuttings are extremely slow to root (Hogan 2008). The largest seen in research for the current work is a specimen of 5 m planted against the gable end of Tony Avent’s house at Plant Delights Nursery, Raleigh, North Carolina, now reaching above the roof line. This was grown from seed obtained from the Kunming Botanical Garden in 1996 and was planted out in 1999, since when it has withstood –10 ºC with only leaf-tip damage (T. Avent, pers. comm. 2006). Clearly thriving in the North Carolina heat, it seems also to do quite well in sheltered sites such as the woodland garden at Heronswood Nursery. Heronswood has sold Dan Hinkley’s collection (DJHC 549) from 1600 m in Yunnan in 1996. In Europe E. populnea is very rare, but it is growing – very fast – at Tregrehan, reaching 3 m in three years after accession. It clearly enjoys a mild, moist situation.
The attractive leaves are dark green (bronzed when young or after a cold spell), and are said to tremble on the tree like those of an aspen in a light breeze, but it is the large leathery stipules pointing straight up that give the shoot its distinctive appearance. The growth pattern is curious as the terminal bud is suppressed and new growth continues from below the apex of the previous shoot, giving the stem a somewhat zigzag look.