Tree Ferns

Tree ferns in the landscape command the attention of both devoted gardeners and casual passersby. Their stately form resembles that of the palm tree and evokes a feeling of the quintessentially exotic. This volume is the source for information on the living tree ferns. It surveys families, genera, and species, including those suitable for the home garden. It offers up-to-date taxonomy and detailed descriptions as well as in-depth coverage of everything from tree fern use to conservation. In recognition of the horticultural importance of tree ferns, the authors provide extensive cultivation information, including propagation, and diseases and pests.

Young uncurling fronds of tree ferns are often eaten in the wild by animals and birds. Humans have also used tree ferns as a food source. The Aboriginal peoples of Australia, the peoples of Hawaii, India, Madagascar, New Guinea, New Caledonia, and the Maori in New Zealand are known to have used the pith from the center of the trunk as a starch source. The young uncurling fronds have also been eaten. This material is often full of silicates and resinous compounds and remains an acquired taste. For a short period in the 1920s, Cibotium starch was extracted in Hawaii commercially for laundry and food use (Nelson and Hornibrook 1962).

Several tree ferns have toxic or therapeutic properties; some have been explored for antiviral and medicinal uses. About 300 B.C., Theophrastus recommended oil extracted from ferns to expel internal parasites. Cyathea manniana (also called C. usambarensis) from East Africa has been used by the Chagga and by German troops in the First World War as an anthelmintic (Mabberley 1997). However, excessive or prolonged use is reported to cause blindness. The sappy gum from the large tree fern C. medullaris (native to the New Zealand region) is likewise a vermifuge. This gum is happily also a treatment for diarrhea.

Cyathea medullaris has many further uses, with extracts used for easing boils (T. Bell 1890). The slimy material from the interior of a young uncurling frond has also been rubbed on wounds or used in various ways to relieve sores, saddle sores on horses, swollen feet, and sore eyes (three applications per day were advised). The young fronds have also been boiled and the liquid drunk to assist the expulsion of afterbirth (O. Adams 1945). The small scales on the fronds of this species are often an irritant and are reported as having been used by inventive children as itching powder. Other members of the genus Cyathea provide a variety of medicinal uses. In Fiji, infusions made from frond material of C. lunulata were used to treat headaches as well as taken by expectant mothers to shorten the period of labor. On Pohnpei, also in the Pacific, fronds of C. nigricans were pounded, squeezed, and the liquid drunk as a contraceptive; there is no record of its success or otherwise. In Malesia, stems and frond extractions of C. moluccana have been used to poultice sores. (For further discussion see Burkill 1935, Cambie and Ash 1994, and Cambie and Brewis 1997.)

The use of tree fern fronds, stipes, scales, and trunks to treat wounds is widespread. Frond material of Cyathea mexicana (also known as Alsophila firma) has been used in Mexico to treat hemorrhaging. The four Hawaiian species of Cibotium are also traditionally used as a wound dressing, as is C. arachnoideum in Malaysia and the Indonesian portion of Borneo. Rhizome hairs from this latter species have also been used to staunch blood loss from open wounds. Similar use as a wound dressing has been made of Cyathea dealbata by the New Zealand Maori. The pith of this plant was used as a poultice for cutaneous eruptions. Ponga powder, probably from C. dealbata, was used by early New Zealand settlers for the reduction of fever, though its effectiveness is not recorded. A surviving package of "Mrs Subritzky's Ponga Powder" can still be found in the Wagner Museum, Northland, New Zealand (Brooker et al. 1981).

Cibotium barometz, from China and Malaysia, is still used medicinally. Hairs of the rhizome and stipe may be charred or used fresh as a wound dressing, and the fronds are used to ease fainting. This short fern, with its distinctive furry trunk, has long been considered to have magical properties. The rhizome (turned upside down with bud and four leaf bases) was passed off as the "vegetable lamb," a strange beast that was thought to be half animal and half plant. Stories of a vegetable lamb, or organism sharing both plant and animal characteristics, date to the time of Christ. One of the early descriptions may be found in Talmud Ierosolimitanum (A.D. 436). In the 14th century, John Mandeville brought to England the story of a fruit that enclosed a "a beast as it were of fleshe and bone and bloud, as it were a lyttle lambe without wolle" (Ashton 1890). There is no direct proof that these early stories specifically concern C. barometz, and they may refer to cotton or some similar plant. However, these descriptions have become mingled with later stories, specifically those concerning the Scythian lamb or lamb of Tartary, from India and Asia; the specific name barometz is a Tartar word, meaning lamb.

By the 16th century, even respectable scholars believed in the existence of this beast. Many early illustrations seem to show a dead dog supported on a stalk. In the early 18th century, several vegetable lambs were exhibited at the Royal Society, London. One of these specimens remains in the 18th-century collection of Hans Sloane, now in the Natural History Museum, London. There is little doubt that this lamb is formed from a rhizome of Cibotium barometz. In the 17th and 18th centuries, these lambs were fashioned by the Chinese to use as toys and charms to ward off evil.