This species, as interpreted in Flora of New Zealand, has the following distinguishing characters: Branchlets finely downy. Leaves of rather spongy texture, narrow-lanceolate, about 11⁄2 in. long, 1⁄4 in. wide; leaf-bud sinus present, though sometimes very small. Racemes longer than leaves, sometimes very much longer; pedicels long, bracts small and narrow. Corolla white or pale coloured; tube not much longer than calyx. Capsules glabrous, about twice as long as calyx.
Native of the South Island of New Zealand, mainly west of the divide, found in damp places and attaining about 6 ft in height. A plant at Kew on the Temperate House Terrace is of compact habit and bears in July a profusion of racemes up to 6 in. long – a remarkable length considering that the leaves are only 1 1⁄4 in. or slightly more long.
Although H. gracillima is recognised as a species in Flora of New Zealand, similar plants might arise from the crossing (in the wild or in cultivation) of H. salicifolia with certain species with shortish leaves. It has even been suggested that it might be a hybrid between H. salicifolia and H. ligustrifolia, though the latter species is confined to the northern part of North Island.
H. × divergens (Cheesem.) Ckn. – A shrub 2 to 5 ft high; young branchlets finely downy. Leaves 3⁄4 to 11⁄4 in. long, up to 1⁄2 in. wide, narrow-oblong or elliptic-oblong, flat, glabrous, midrib raised beneath. Racemes densely flowered, up to 3 in. long (sometimes longer); bracts about equal to the pedicels. Flowers white; corolla-tube rather broad, about as long as the calyx and shorter than the corolla-lobes. A hybrid described from Nelson province, South Island. It is suggested in Flora of New Zealand that the parentage might be H. gracillima × H. elliptica.