Rhizanthella

Rhizanthella, commonly known as underground orchids, is a small epiparasitic, achlorophyllous, subterranean genus of orchid endemic native to Australia. It is abbreviated in trade journals as Rhi.

These orchids are rare and their status is considered vulnerable to critical, mostly due to loss of habitat. They live underground in symbiosis with mycorrhizal fungi. These subterranean rhizomes or tubers are short and thickened, without roots, serving as storage for the orchid. The leaves are absent.

When the orchid prepares to flower, the solitary inflorescences break through the surface, beneath the leaf litter. The terminal inflorescence is racemose. It gives rise to a cluster of small, tubular, hermaphroditic flowers. The fragrant flowerheads are about 5 cm wide and contain numerous, inward-facing, small flowers.

Pollination is carried out by small flies or insects, even underground by termites or gnats. The fruit is a fleshy, indehiscent drupe with about 250 minute seeds.

Their discovery in 1928 caused such an excitement among orchid lovers, that a wax model had to be toured around Britain.

Reference works

• George, A. S. (1981). Rhizanthella-The Underground Orchid of Western Australia. Proceedings of the Orchid Symposium, 13th International Botanical Congress 77-78.
• Dixon, K. W., et al. (1990). The Western Australian fully subterranean orchid Rhizanthella gardneri. Orchid Biology, Reviews and Perspectives. V. J. Arditti. Portland, Oregon, Timber Press. 5: 37-62.
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