Rhizanthella

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Rhizanthella gardneri
Plant Info
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Scientific classification
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Type Species
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Species
Rhizanthella gardneri Rhizanthella omissa Rhizanthella slateri
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Rhizantella R.S.Rogers 1928 is a small epiparasitic, subterranean genus, belonging to the orchid family (Orchidaceae), endemic to Australia. It is abbreviated in trade journals as Rhi.

It consists of only three species

• Rhizanthella gardneri R.S. Rogers 1928 (type species) : Gardner's Underground Orchid
• Rhizanthella omissa D.L.Jones & M.A.Clem. 2006 : Lamington Underground Orchid
• Rhizanthella slateri (Rupp) M.A. Clem. & P.J. Cribb 1984 : Eastern Underground Orchid

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

The solitary inflorescences, when as flowering is approaching, 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 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.
• Dixon, K. (2003) Underground Orchids on the Edge. Plant Talk, 31: 34-35.
• Jones, D.L. & Clements, M.A. (2006). Rhizanthella omissa, a new species of underground orchid from south eastern Australia. The Orchadian, vol. 15, no. 3, pp. 131-133.

Further reading

• Hoffman, N., Brown, A. (1998). Orchids of South-west Australia. University of Western Australia Press, Nedlands.Rev. 2nd ed. with suppl. ISBN 1876268182
• Jones, David L. (2006). A complete guide to native orchids of Australia: including the island territories. Frenchs Forest. ISBN 1-8770-6912-4.