Shrub or tree 3–8(–20) m. Bark rough, greyish brown. Branchlets brown, sparsely covered with white pubescence when young. Leaves bipinnate; pinnae three to six pairs, each 10–20 cm long with secondary stipules at the base; pinnules 7–15 pairs, opposite, oblong to obovate, 1.5–4 × 0.5–1.5 cm, pubescent on both surfaces; petiole 4–8 cm long; stipules inconspicuous. Heads two to seven, arranged in axillary or terminal panicles; peduncles 4–7 cm long. Flowers 25–30 per head, white, turning yellow, dimorphic; terminal flower sessile, 2–2.5 cm long; lateral flowers pedicellate. Legume linear to narrowly oblong, 7–16 × 1.5–3.5 cm, dark brown, obtuse to acute at both ends; dehiscent, with 4–12 seeds. Flowering after leaves have emerged and fully opened; June (USA). Nielsen 1981. Distribution CHINA: Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Shanxi, Sichuan, Zhejiang; INDIA; JAPAN: southern Kyushu; MYANMAR; NORTH KOREA; SOUTH KOREA; TAIWAN; VIETNAM. Habitat Thickets and sparse forest between 500 and 2000 m asl. USDA Hardiness Zone 7a/8b. Conservation status Not evaluated. Cross-reference K129. Illustration NT129. Taxonomic note Chakrabarty & Gangopadhyay (1996) place A. kalkora in synonymy with A. garrettii I.C. Nielsen, but list Mimosa kalkora as a synonym of
A. julibrissin. This approach does not appear to have been widely accepted (see, for example, Ohashi & Endo 2001, Wu & Nielsen 2006). The Korean Albizia coreana is considered synonymous with A. kalkora by Lee (2002) and IPNI (2005). Albizia kalkora is in limited cultivation in the United States at the present time, often labelled A. coreana. It can form big trees, with spreading umbrageous crowns, covering themselves with white powder-puff inflorescences. The foliage of A. kalkora is much coarser and less attractive than that of the familiar A. julibrissin. Its introduction to the United States is attributed to Frank N. Meyer of the US Department of Agriculture’s Foreign Seed and Plant Division. Meyer collected seed near Boshan, Shantung, China in September 1907 (PI 21969), and from Pangshan, Chihli (PI 22618) in November 1907 – where, he states, the ‘species is quite distinct from Albizia julibrissin, which is much more floriferous and of which the leaves, though much finer pinnated, are much smaller’ (USDA 1909). There is still a notable specimen at the old USDA Plant Introduction Station in Savannah, Georgia, presumably from these collections, and it would seem that it is from this source that the species has achieved a limited commercial distribution in the southern United States (R. Olsen, pers. comm. 2007). As an example, a seedling of A. kalkora purchased from Woodlanders Nursery, South Carolina in 1989 had developed into a fine tree of 12 m at the JC Raulston Arboretum, before it was removed not long ago (V. Tyson, pers. comm. 2007). More recent introductions have come from NACPEC expeditions, including seedlings still under glass at the Morris Arboretum from a collection made in Shanxi Province, China in 2002. It is anticipated that these will be hardy in the Philadelphia area (A. Aiello, pers. comm. 2007). Concerns have recently been raised over the potential for self-sowing of A. kalkora, one naturalised population being known from the campus of Duke University in Durham, North Carolina. In this area hybrids with A. julibrissin have also been found (Cook 2006), confirming suspicions long held by J.C. Raulston, R. Olsen and others.
Trees labelled Albizia coreana are growing at the US National Arboretum Woody Landscape Plant Crop Germplasm Repository at Glenn Dale, Maryland, from collections made at Chollipo Arboretum and at Mount Yudal, South Korea, in 1984 and 1985, respectively. It is probable that all material of ‘A. coreana’ in the United States is derived from these two collections (R. Olsen, pers. comm. 2006). At the JC Raulston Arboretum one such specimen received from the National Arboretum in 1988 (NA 55290) had reached nearly 12 m in 2006, and is an attractive tree. The species is in cultivation in New Zealand (for example, at Eastwoodhill, as A. coreana) but no specimens have been traced in Europe, or in western North America. It would seem to need hot and humid summers to thrive.