A large deciduous shrub, 7–9 m, with arching branches that are weakly quadrangular when young. Bark reddish-brown when young, becoming pale and somewhat shaggy with age, peeling in long strips; shoots slightly pubescent when young. Leaves opposite, entire, lacking stipules; petiole short, 10–15 mm, reddish, with red warts and some hairs; lamina ovate to oblong-ovate, 8–15 × 5–9 cm, leathery, opening pale green and sparsely hairy, becoming dark green and more or less glabrous above, with a few hairs on the main veins, with three conspicuous veins from the base, veins prominent and sparsely pubescent below, base obtuse to subcordate, apex acuminate to long acuminate. Inflorescence a terminal panicle composed of numerous small clusters (capitula) of fragrant flowers. Each capitulum is formed of a sessile whorl of two opposite 3-flowered cymes and a terminal bud, with 2 pairs of decussate involucral bracts and 12 bracts. Involucral bracts ovate and persistent in fruit, glabrous to sericeous, becoming longer and covering bracts and ovaries. Sepals 5, 2–2.5 mm, equal to ovary in length at flowering (when pale green), slightly protruding from involucre, but expanding to 7–10 mm after flowering, when often strongly tinged red. Corolla 10–15 mm long, c.16 mm across, tubular-funnelform; white, with a faint greenish flush externally, tube strongly curved at base and slightly swollen with a nectary inside, lobes 5–7 mm, regular, slightly downcurved, densely adpressed-hairy. Stamens 5, inserted between the corolla lobes, exserted; filaments inserted at middle of corolla tube, hairy, free only in uppermost portion; anthers cream, becoming brown. Ovary 3-locular, 2 locules with numerous sterile ovules, remaining locule with 1 fertile ovule. Style 7 mm, hairy except at base, stigma pale green, discoid. Fruit a leathery achene, 10–11 mm, cylindrical, silky-hairy crowned with a persistent and enlarged calyx, red on sunny side, containing one seed 5–6 mm long (Coombes 1990; Yang et al. 2011).
Distribution China Anhui, Hubei, Zhejiang
Habitat Scrub, woodlands and at the edge of broadleaved evergreen forests, often on cliffs, 600–1000 m.
USDA Hardiness Zone 5(-4)
RHS Hardiness Rating H6
Conservation status Vulnerable (VU)
Heptacodium was discovered by Ernest Wilson in western Hubei in 1907, growing on cliffs at ‘Hsing-shan Hsien’, presumably today’s Xingshan, but did not collect seed. The honour of its introduction to the West fell to members of the 1980 Sino-American Botanical Expedition (SABE), although the seed was gathered from a specimen transplanted from a wild population in the Zhejiang Province Preserve growing at Hangzhou Botanical Garden. The species was not included among the numbered SABE collections, but regarded as ‘supplemental’, with the two collectors using their own numbering sequence, to result in the batch SAS 10 (S. Spongberg) going to the Arnold Arboretum, and TRD 10A (T. Dudley) going to the United States National Arboretum (USNA) (Dosmann & Del Tredici 2003). Further seed was distributed by Hangzhou Botanical Garden in 1980–81, from where it was received at the Hillier Gardens (Clarke 1988), and from Shanghai Botanical Garden in 1992. It is rare in the wild and it seems certain that the genetic variability in cultivation is also low.
Seedlings from the early importations did very well, and remain as large, multistemmed shrubs at both USNA and the Arnold Arboretum. Most specimens in cultivation seem to be derived from the latter – it was soon recognised that the species had great ornamental potential and distribution of material started early. Seedlings from both the 1980 and 1981 seed first flowered in 1985, in Vancouver as well as on the East Coast, and large quantities of seed were collected at the Arnold Arboretum (at least) making it possible to experiment with germination techniques as well as hastening the plant’s distribution in cultivation (Koller 1986). In Britain, it first flowered at the Hillier Gardens in 1987, having been planted out earlier that year (Coombes 1990). It can now be said to be a commonly grown plant across North America and Europe, and freely available in the nursery trade on both continents.
In full growth the plant is very distinctive, with pendulous dark green leaves, often somewhat in-rolled to show paler undersides. With their conspicuous venation they are rather handsome, but they do not turn any significant colour in autumn, and in many cases they fall late without colouring. The flowers appear in late summer, usually being at their best in August and September, but they can persist well into autumn, to be finished off by the first frosts. Flowers will appear earlier in warm areas than in colder sides, as growth is slower is cooler climates.
The white flowers are individually small, but it is free-flowering (on new growth) and within the inflorescence individual capitula, with their 3+3+1 arrangement (from which both the generic and common names are derived), are worth close inspection. They’re also pleasantly fragrant, being reminiscent of its relative Lonicera, and attractive to butterflies. After flowering, especially in a warm, dry autumn, the enlarged calyx becomes tinged with red to varying extent. These can be a colourful feature in their own right; ‘The effect of all the tiers of these exotic fruits with seven splendid purple crowns is spectacular’ (Tripp & Raulston 1995). In consequence, it is a very useful late-flowering shrub, becoming large when fully grown but kept much smaller by judicious pruning. It is probably best as a background planting for smaller shrubs, but consideration should be given to ensuring that the pale stems can be seen and appreciated in winter. It is tolerant of most soils, though should not become too dry in summer, and it is very hardy.
Heptacodium is reasonably easily propagated from seed; no chilling period is needed, with good germination occurring in consistently mild conditions (Koller 1986). Propagation is usually effected by cuttings, with softwood or semi-ripe material rooting easily in late spring or early summer, under mist or high humidity, with hormone treatment, but late summer firm cuttings are not very successful (Dirr 2009). Fortunately, Heptacodium has shown no signs of being invasive in any part of the US (P. Del Tredici, pers. comm. 2013).