Sm.
Description
Leucosceptrum canum is a soft-wooded shrub or small tree of the Himalaya and southwestern China, distributed through China, Nepal, India, Bhutan and Myanmar and east to Indochina (CN, NP, IN, BT, MM, VN, TH, BD, LA, with further records), one of the more frequently collected species here with about 515 occurrences. It grows in moist temperate forest, on shaded slopes, ravine sides, forest margins and clearings, typically in the warm- to cool-temperate belt. The gatherings cited are from the Mo-Chu valley in Bhutan at 1900 m and from Trisuli in Nepal at 2700 m, both flowering in October, reflecting its autumn-to-early-winter blooming in the mid-montane forest zone.
The plant is a coarse shrub or small tree with stout, four-angled young branches densely clothed, like the leaf undersides and inflorescence, in a greyish (canous) tomentum from which the epithet derives. The leaves are large, opposite, elliptic to oblong-lanceolate, with a serrate margin, an acuminate apex and prominent venation. The flowers are crowded into a dense, terminal, cylindrical spike-like thyrse with conspicuous bracts; the calyx is tubular and five-toothed, and the white to pale yellow, two-lipped corolla has a short tube and exserted, declinate stamens. The fruit comprises four small nutlets (an eremocarp) enclosed in the persistent calyx.
Leucosceptrum is a small genus placed in the subfamily Lamioideae (or basal lineages) of the Lamiaceae and is of phylogenetic interest as part of an early-diverging Asian woody assemblage allied to Comanthosphace. The conspicuous, nectar-rich autumn inflorescences attract bees, butterflies and birds, and the species is notable for the production of defensive sesquiterpenes secreted by glandular trichomes. Widespread and common across the Himalaya into China, L. canum is of no conservation concern and is locally valued for fuel and as a bee plant.
Author: Sm. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Labiatae of the Himalaya (Lamiaceae revision)