Conospermum leianthum is a species of flowering plant in the family Proteaceae and is endemic to the south-west of Western Australia. It is a shrub with thread-like leaves, and panicles of white and more or less purple, tube-shaped flowers.
Conospermum leianthum is a shrub that typically grows to a height of up to, its leaves erect, s-shaped or curved, long and long. The flowers are arranged in panicles in leaf axils, on a peduncle long, each branch of the panicle ending in a dense head, sometimes longer than the leaves. There are hairy, kidney-shaped bracteoles long and wide. The perianth is tube-shaped, long, white with a more or less purple base, the upper lip usually long and wide, the lower lip joined for about, long and . Flowering time depends on subspecies, and fruit is a nut covered with woolly, gold-coloured hairs, and long and wide.[1]
This species was first formally described in 1870 by George Bentham who gave it the name Conospermum polycephalum var. leianthum in his Flora Australiensis,[2] from specimens collected by George Maxwell. In 1904, Ludwig Diels raised the subspecies to Conospermum leianthum in Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie,[3] and in 1995, Eleanor Marion Bennett described C. leianthum subsp. orientale in the Flora of Australia, and that name, and the autonym are accepted by the Australian Plant Census:
The specific epithet (leianthum) means 'smooth flowered'.[8]
Conospermum leianthum is common in coastal areas between Ravensthorpe and Cape Arid National Park where it grows in sandy soils. Subspecies leianthum is found between Forrestania and east of Esperance in the Coolgardie, Esperance Plains and Mallee bioregions of south-western Western Australia. Subspecies orientale occurs from east of Esperance to Israelite Bay in the Esperance Plains and Mallee bioregions.
Both subspecies of C. leianthum are listed as "not threatened" by the government of Western Australia.