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A dwarf shrub of neat habit, 3 to 10 ft high; young shoots slender, covered with a dense grey down. Leaves oblong or obovate, tapered to a short stalk at the base, either rounded or pointed at the apex; margins entire or occasionally sparsely toothed, recurved, 1⁄4 to 5⁄8 in. long, 1⁄8 to 1⁄4 in. wide, dark bright green above, blue-white beneath and covered with silky hairs. Catkins produced in late summer and autumn from the leaf-axils of the current year’s growth; females 11⁄2 in. long, 1⁄2 in. broad; males shorter. Stamens two, but with their stalks united to the summit (as in S. purpurea); bracts of catkins narrowly lanceolate and pointed. Bot. Mag., t. 9079.
A native of Western Szechwan, China, and abundant in river-beds up to 9,000 ft. It was introduced to the Arnold Arboretum by Wilson by means of cuttings in 1908 and a plant was obtained for Kew in 1910. This was female, and probably most of the plants originally grown in Britain descended from it; the more attractive but rarer male form is also in cultivation (both sexes were collected by Wilson in 1908). It is not unusual for normally spring-flowering species to produce the occasional catkin on summer shoots, but S. bockii is almost unique in regularly flowering late in the season on the growing shoots. It is then very ornamental.
S. bockii is probably not specifically distinct from S. variegata Franch. This species, apparently known in its typical state only from the gorges of the Yangtse Kiang, is prostrate, but in its essential characters scarcely differs from S. bockii and the two were united by K.-S. Hao in 1936 under the name S. variegata, which has priority. The two species were kept apart in Plantae Wilsonianae largely because of a biological difference in the plants seen by Wilson: the Yangtse plants are under water during the summer and flower on the ripened wood in late autumn or early winter; S. bockii in W. Szechwan (as seen and introduced by Wilson) produces its catkins in late summer and autumn on young stems while these are still elongating. But the whole complex (which also includes S. duclouxii Lévl. from Yunnan) seems to vary in the rhythm of its growth and flowering.