An evergreen or semi-evergreen shrub 2 to 5 ft high in the wild; stems four, lined or four-angled under the inflorescence. Leaves shortly stalked, lanceolate to narrow-ovate, 11⁄4 to 21⁄2 in. long, 1⁄2 to 1 in. wide (rarely to 3 in. long, 13⁄4 in. wide), tapered at the apex to a blunt point, but sometimes acuminately pointed or obtuse. Inflorescences with mostly one to seven flowers (occasionally up to eleven). Flowers varying in colour from deep golden yellow to pale yellow-cup-shaped, 11⁄2 to 2 in. wide. Sepals broadly spathulate-obovate to almost circular or oblate, always rounded at the apex. Stamens in five bundles, one-quarter to one-third as long as the petals. Styles one-fifth to one-half as long as the ovary.
H. hookeranum was described from a specimen collected in the Nilghiri Hills of southern India, but is also found in the Himalaya from Nepal eastwards, and in Burma and Thailand. The date of first introduction is not certain, but it has probably been in cultivation off and on since early in the 19th century, and had certainly been introduced from Sikkim by 1911. In recent years seeds have been sent from the Himalaya and bordering regions, two of the most recent introductions being by the late Frank Kingdon Ward from the Triangle, Burma, and by Cox and Hutchison from the Assam Himalaya. The hypericum described in previous editions under the name H. hookeranum is H. lobbii, and the date of introduction, given as ‘shortly before 1857’ in some works of reference, is of that species.
Judging from herbarium specimens, H. hookeranum is variable in habit, in size and shape of leaf, in the number of flowers in each inflorescence, and in their size. The finest Himalayan forms have still to be introduced, but might not prove hardy.
Despite its variability, H. hookeranum is a well-marked species, at once recognisable by the short styles and stamens in combination with the sepals smoothly rounded at the apex.
cv. ‘Rogersii’. – This superior form of H. hookeranum, with deep-yellow flowers, was raised in the garden of Sir John Ross of Bladensburg at Rostrevor House, Co. Down, from seeds collected in the mountains of Burma shortly before 1921 by an officer of the Indian Forestry Service. It reached commerce in the 1930s but has been displaced by its hybrid ‘Rowallane’. The true plant is now rare. Plants seen in two gardens in 1970 under the name ‘Rogersii’ proved to be ‘Rowallane’.
H. (hookeranum‘Rogersii’ × leschenaultii) ‘Rowallane’. – This beautiful hybrid arose as a self-sown seedling in the garden of H. Armytage-Moore at Rowallane, Co. Down. The flowers are bowl-shaped and deep yellow as in the first-named parent, but the influence of H. leschenaultii shows in their large size – up to 3 in. wide. From both parents it differs in the shape of the sepals, which are rounded at the apex, not acute or subacute as in H. leschenaultii; and whereas the sepals of H. hookeranum are smoothly rounded at the apex and obovate-cuneate or almost circular, those of ‘Rowallane’ are more or less apiculate, and the roundish upper part is usually rather abruptly narrowed to a claw.
‘Rowallane’ is not quite hardy south of London, but if severely cut by frost will usually break again from the base and flower late in the same season, while slight frost-damage is of no account, some pruning in spring being always desirable. In the milder parts it will attain a height of 6 ft.