A shrub, evergreen in mild climates, lax in growth, ordinarily 4 to 8 ft high; branches slender, reddish brown. Leaves more or less shortly stalked, ovate-oblong, bluntish at the end, rounded at the base, 11⁄2 to 21⁄2 in. long, 3⁄4 to 11⁄2 in. wide, dark, slightly glaucous green above, more definitely glaucous and thickly sprinkled with translucent dots beneath. Flowers rich yellow, 21⁄2 to 3 in. wide, produced singly or in threes (sometimes in sevens) at the end of the shoot. Petals 1 in. wide, rather concave, roundish obovate, slightly overlapping. Sepals 3⁄8 to 5⁄8 in. long, narrowly oblong or narrowly elliptic to oblanceolate, acute at the apex. Stamens less than half as long as the petals, very numerous, arranged in five bundles. Ovary conical, tapering upward to the five recurved styles, which are half as long as the ovary, or even shorter. Bot. Mag., t. 9160.
Native of Java and other parts of Malaysia; discovered on the Javan mountains by Leschenault about 1805. The date of its introduction is not definitely known, but it was flowering in Mr Riall’s garden at Old Conna Hill, Co. Wicklow, Eire, in July 1882. It is, in combined size and richness of colouring, the finest flowered of all hypericum species. It is not quite hardy at Kew, where it has been grown in a practically unheated house, making shoots half to fully a yard long in a season, attaining a height of 12 ft or more and flowering during the summer and autumn months. In the milder parts it is hardy in the open ground, but even there it is better on a wall, owing to its rather lank habit.
It belongs to the same group as H. patulum (section Ascyreia) and is quite closely allied to H. hookeranum, which it resembles in its short stamens and styles, but is distinguished by its ‘very variable but always herbaceous and spreading calyces with their acute or acuminate, often unequal sepals and the rather large, long-tapering, conical capsules’ (Stapf in Bot. Mag., loc. cit.).
At the present time (1971) some plants grown as H. leschenaultii are really H. augustinii (q.v.).