A small deciduous tree to about 20 ft high. Leaves obovate, up to 27⁄8 in. long, 13⁄8 in. or slightly more wide, acuminate at the apex, cuneate to rounded at the base, finely toothed, glabrous on both sides except for some stellate down on the midrib beneath; petiole to about 1⁄4 in. long. Flowers white, about 1 in. wide, arranged in cymes of three to five at the ends of lateral shoots which are leafy at the base; pedicels 1⁄4 in. long, slender. Stamens twelve to fourteen, with yellow anthers. Fruits woody, indehiscent, obovoid but with a conical apex, about 5⁄8 in. long, 1⁄2 in. wide.
S. xylocarpa, the type of the genus Sinojackia, was discovered in 1925, and described by Dr Hu four years later. The type-specimens were taken from a single tree growing at a resort in the suburbs of Nanking known as the Sen-Tai-Tung cave. Shortly afterwards this tree, the only one found, was cut down during roadmaking, and the seeds that had been distributed to botanical institutions in Europe and America were immature, and failed to germinate. Thus, for a brief space, it seemed as if this new genus was extinct. Then, in 1933, S. xylocarpa was found to be quite common in the hills of Pukow, on the other side of the Yangtse from Nanking, and was successfully introduced to cultivation later in the decade (H. H. Hu, in Journ. R.H.S., Vol. 63 (1938), p. 383, and New Fl. & Sylv., Vol. 13 (1940), p. 150).
Dr Hu considered S. xylocarpa to be a much finer species than S. rehderiana, described below, but it seems to be less common in gardens. It is available in commerce.
S. rehderiana H. H. Hy – A deciduous shrub or small tree, allied to S. xylocarpa, but with elliptic to elliptic-obovate leaves, laxer inflorescences, rather smaller flowers, and much narrower fruits, about 1 in. long and 1⁄4 in. wide, beaked at the apex and tapered at the base. Bot. Mag., n.s., t. 466.
This species was discovered by Dr Hu in 1930 in the hills above Nachang, the capital of Kiangsi province, and was introduced by him to Britain and other countries in the same year. It is perfectly hardy and flowers well, but is horticulturally too similar to the halesias to have become popular and is rarely seen outside collections.