Hydrangea robusta - Robust Hydrangea

Robust Hydrangea is a shrub or small tree, 2-3 m tall. Flowers are borne in corymb-like cymes, lax, long, up to 30 cm wide in fruit; flower-cluster-stalk thick, 4-angled. Sterile flowers have sepals 4-5, purplish to white, broadly ovate, round, or broadly round, 1.2-3.8 x 1.3-3.5 cm, margin entire, toothed, or sawtoothed. Fertile flowers have sepal-tube cup-shaped, 1-1.5 mm; teeth ovate-triangular, 0.5-1 mm. Petals are purple, ovate-lanceshaped, 2-3 mm. Stamens are 10-14, unequal, longer ones 6-6.5 mm. Styles are 2, spreading to recurved, 1-2 mm in fruit. Branchlets are brown, usually 4-angled, becoming hairless. Leaf-stalks are thick, 3-15 cm; leaf blade elliptic, broadly so, or oblong-ovate to broadly ovate, 9-35 x 5-22 cm, papery, below densely gray-white velvet-hairy to sparsely brownish bristly, above bristly, secondary veins 8-13 on both sides of midvein, base blunt, flat, rounded, or somewhat heart-shaped, margin irregularly doubly sawtoothed, tip pointed to tapering. Capsule is cup-shaped to bell-shaped, 3-4.5 x 3.5-5 mm, tip flat; persistent styles spreading to recurved. Robust Hydrangea is found in dense to sparse forests or thickets in valleys, along stream banks, or on mountain slopes or tops, at altitudes of 700-2800 m, from Nepal to East Himalaya, Bangladesh, China. Flowering: July-August.