Renanthera coccinea is native to Myanmar, China, Laos, Thailand and Vietnam. In China, they were found in the Kwangtung Province (Guangdong) and on the island of Hainan and Taiwan. On the island of Hainan they grew on the branches of trees or on rocks in rare forests or on their edges, along the ravines, at an altitude of about 1,400 m. In Thailand, they were found in several places in the east and south-east inland and near Ranong on the peninsula Thai. In Vietnam, this species was encountered in the north, along the border with China, near Ha Giang at an altitude of 650-1200 m. It is a giant sized, hot to cool growing monopodial lithophyte in full sun or epiphyte in primary forests, which reaching over 100 cm in size, with a simple to branched, elongate, stout, 100 cm long stem carrying many 2 ranked, thick, fleshy, oblong to shortly lorate, 7-8 cm long and 1.5-3.3 cm wide leaves. The Scarlet Renanthera blooms in the spring on an axillary, lateral, paniculate, 60 to 90 cm long, divaricate, laxly several to many flowered inflorescence. The flowers are deep red in color with yellowish spots on the dorsal leaf, inner whorl petals and lip. Upper sepals straight, oblong, with blunt tip and slightly wavy margins. The lateral sepals at the base are narrow, then expand, forming an almost oval surface with a blunt apex and wavy margins. The oblong petals are arranged horizontally or pointing upward at a slight angle. Their edges are straight, the apex may slightly curl upward. Three-lobed lip with spur is much less than the rest of the flower. The lateral parts of the lip are triangular, the middle part is ovate, its apex is bent back and almost touches the spur.
