Encephalartos ferox G.Bertol. (Zamiaceae)


Encephalartos ferox is part of an ancient lineage of plants, growing at the time the dinosaurs roamed the earth. This cycad hides numerous secrets.

The genus name is the key to the first of these hidden stories. From the Greek en (within), cephale (head) and artos (bread), encephalartos could be translated literally as 'within the head there is bread'. Indeed, the plant's stem has been used as a source of sago, a traditional starchy foodstuff. More conventionally, sago comes from palms and other cycads, but local people on the southeastern coast of Africa, whence Encephalartos originates, have used it for its starch content. However, along with other cycads, Encephalartos ferox contains another, more sinister presence; a neurotoxin. This neurotoxin is an amino acid, beta-methylamino-L-alanine, which must first be carefully removed from the sago by repeated washings before the starchy product can safely be consumed. Its presence in cycads has been linked to neurodegenerative diseases in populations who consume cycads directly or indirectly in their traditional diet.

Another secret, hidden from the naked eye, is that photosynthetic, nitrogen-fixing cyanobacteria ('blue-green algae') live in specially adapted 'coralloid' roots near the surface of the soil. The bacteria form symbiotic (mutually beneficial) relationships with the plant; cyanobacteria and cycads sharing nutrients.

Encephalartos ferox produces separate male and female plants, and is threatened by over-collecting for traditional medicine and horticulture, being relatively easy to cultivate and architecturally striking. Thieves have been known to remove mature plants using chainsaws, then to 'pot' these rootless plants up for sale at exorbitant prices. Consequently, Encephalartos ferox appears on the IUCN 'red-list' of Threatened Species as Near-Threatened.

When the Botanic Garden staff noticed that our Encephalartos ferox had produced a female cone (reproductive structure) some years ago, they saw an opportunity to play a small part in the conservation of this endangered species. There was no male plant growing at the Garden at the time, so the Glasshouse Curator sent out a lonely-hearts advert to other glasshouse collections around the UK. Pollen was sent from the Royal Botanic Gardens, Kew and the glasshouse staff did their best weevil (snout beetle) impression and pollinated the female cone. They were rewarded for their efforts with a tremendous production of seed, which when mature was sown and germinated to produce about 100 young plants. These plants have now been distributed to other botanical collections, with one growing happily in the Palm House.

Further reading

Jones DL 2002. Cycads of the world: ancient plants in today's landscape. Reed New Holland.

Norstog KJ, Nicholls TJ 1998. Biology of cycads. Cornell University Press.

Alison Foster

BBC Radio Oxford clip about this week's plant