Cibotium

Cibotium is a genus of eleven species of tropical tree fern—subject to much confusion and revision—distributed fairly narrowly in Hawaii (four species, plus a hybrid), Southeast Asia (five species), and the cloud forests of Central America and Mexico (two species). Some of the species currently listed in the literature seem to be synonyms or local-variant sub-species. Cibotium glaucum, from Hawaii, is the most frequently encountered Cibotium species in the horticultural trade, together with its sibling species Cibotium chamissoi and the potentially huge Cibotium menziesii. The remaining Hawaiian Cibotium, C. nealiae, is a one-metre dwarf variety, restricted to the island of Kaua‘i, and never seen in the horticultural trade. Precise identification of the Cibotiums is difficult, although all have shiny and rather waxy fronds when viewed from above, with varying degrees of powdery-pale blush when seen from underneath. The dripping forests and stream gulleys of the cloud forests on Hawaii's volcanic slopes are the natural habitat of Cibotium.

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Pressure on Hawaiian Cibotium habitats comes from development encroaching on the forested areas, especially the more accessible lower lying areas which are commercially attractive for land clearance. A less obvious threat comes from an invasive introduced tree fern species: Cyathea cooperi (the most popular garden tree fern in the United States), which has escaped from the islands' suburban gardens and now out-competes the endemic flora. Wind-blown spores from this rapidly growing Australian import can migrate many miles into pristine Cibotium forests. This is a fairly recent phenomenon, but one which may eventually have grave consequences for the tree fern ecosystem in Hawaii.

The other Cibotiums that often surface in botanical collections are Cibotium schiedei and Cibotium regale (Mexico), plus Cibotium barometz (Asia). The latter species is best known for its role in ancient medicine, and even today its hairs are a staple ingredient in ointments used in natural Chinese remedies. The medieval world was beguiled by stories that claimed Cibotium barometz, the "Scythian lamb", was half-sheep and half vegetable.

There are no publicly accessible Cibotium collections growing outdoors in the United Kingdom - although they are sometimes glimpsed in Californian garden designs - but there are two outstanding glasshouse collections at the Royal Botanical Gardens, Kew, and at RBG Edinburgh in Scotland.

Species

• Cibotium arachnoideum
• Cibotium assamicum
• Cibotium barometz - Scythian Lamb
• Cibotium chamissoi - Hawaiian tree fern, hāpu‘u
• Cibotium cumingii
• Cibotium glaucum - Hawaiian tree fern, hāpu`u pulu
• Cibotium menziesii - Hawaiian tree fern, hāpu`u `i`i
• Cibotium nealiae - Hawaiian tree fern, hāpu‘u
• Cibotium regale - Royal cibotium
• Cibotium schiedei - Mexican tree fern
• Cibotium sumatranum

References

• Smith, A.R., K.M. Pryer, E. Schuettpelz, P. Korall, H. Schneider & P.G. Wolf 2006. A classification for extant ferns.PDF (420 KiB) Taxonomy 55(3): 705-731.