A semi-evergreen shrub 4 or 5 ft high, with arching branches; young stems reddish, flattened and four-angled beneath the flower clusters. Leaves very short-stalked, 3⁄4 to 21⁄4 in. long, 1⁄4 to 3⁄4 in. wide, elliptic, oblong-elliptic, or oblanceolate, blunt or rounded at the apex, sometimes shortly apiculate, wedge- shaped at the base, dark green above, pale and slightly glaucous beneath, with the veins, except the marginal loops, scarcely visible. Flowers 11⁄2 to 17⁄8 in. across, borne singly or in cymose clusters of two or three (occasionally up to six); buds ovoid, pointed at the apex. Sepals triangular-ovate to lanceolate or linear-lanceolate, tapered at the apex to a slender point, spreading in the bud-stage and after flowering. Petals golden yellow, spreading. Stamens about three-quarters as long as the petals, in five bundles. Styles free to the base, slightly shorter than the ovary.
Native of Yunnan, China; introduced by George Forrest, who also collected the type material under his number F.19448. This specimen was originally referred to H. patulum var. henryi and the cultivated plants have been grown under this name or as H. kouytchense or H. oblongifolium. The late Dr Stapf recognised that it was a distinct species but it was first described as such by Dr N. K. B. Robson in 1970 (Journ. R.H.S., Vol. 95, p. 494).
This is a very distinct and pretty hypericum, with unusually narrow leaves that colour red in the autumn. As will be seen from the coloured plates accompanying Dr Robson’s article (op. cit., fig. 238 and 240) the flowers resemble those of H. kouytchense in their shape and long stamens, but they are of a deeper yellow and the petal apiculus is not so sharp as in H. kouytchense and its immediate allies. It also grows taller than that species.
The following two species, both at present uncommon in gardens, are placed by Dr Robson in the same group as H. acmosepalum.
H. beanii N. Robson H. patulum var. henryi Bean – This species was described in 1905 (as H. patulum var. henryi) from a plant growing at Kew, raised from seeds sent from southern Yunnan, China, by Augustine Henry seven years earlier. It was distributed by Messrs R. Veitch of Exeter and no doubt by other nurserymen, but was soon superseded by other species that have wrongly been called H. patulum var. henryi in gardens (see H. pseudohenryi below, and H. forrestii). The characters that, in combination, serve to distinguish it from its allies (and from other species with which it might be confused) are: stems slightly flattened and four-lined near the ends and under the flowers; leaves obtuse at the apex, not mucronate; sepals ovate or narrowly so, acute or acuminate at the apex; stamens from one half to almost three-quarters as long as the petals; styles about two-thirds as long as the ovary.
The cultivar ‘Gold Cup’ is near to H. beanii but its leaves are lanceolate, the flower-buds are almost twice as long as wide (not barely longer than wide as in H. beanii and its allies) and the stamens and styles are rather shorter than is usually the case in H. beanii. It is a beautiful variety growing 3 to 5 ft high, with bright yellow cup-shaped flowers shading to paler yellow at the edges of the petals. The leaves turn pale red in the autumn.
H. pseudohenryi N. Robson H. patulum var. henryi sensu Rehd., in part, not Bean – This species, a native of W. China, was introduced by Wilson from the neighbourhood of Tatsien-lu (Kangting) in 1908 (W.1355). It was identified by Rehder as H. patulum var. henryi and at one time was common in gardens under that name but seems to have become rather rare (most of the plants grown under that name arc H. forrestii, q.v.). Its distinguishing characters, in combination, are: branchlets much flattened and four-lined at first, then two-lined, finally terete; sepals ovate or oblong, appressed to the buds and fruits; stamens about three-quarters as long as the petals or slightly longer; styles slightly longer than the ovary. In its long stamens it recalls H. kouytchense, but the petal apiculus is not hooked as in that spccies (q.v.).