The Cycad Collection of Vumba Botanical Garden, Zimbabwe
Volume 2 Number 8 - July 1997
Historically cycads were once one of the major components of the world's vegetation. They were grazed by dinosaurs, but little appears to have changed in their morphology and physiology, let alone their reproductive systems.
As of now there are 185 known species in 10 genera. The genera are, with countries of origin in brackets: Encephalartos (South Africa), Stangeria (South Africa), Bowenia (Australia), Zamia (New World), Cycas (more widespread - Asia, tropical Australia, East Africa, Madagascar and a host of western Pacific islands), Ceratozamia (Mexico), Dioon (Mexico and Honduras), Microcycas (Cuba), Macrozamia (Australia) and Lepidozamia (eastern Australia).
Cycads are toxic to both humans and livestock and have to be treated before consumption. The toxicity is due to glycosides such as cycasin, macrozamin and methylazoxmethanol which cause neurological disorders. To reduce the effects of these harmful substances, cycad seeds, leaves or stem tissues require slicing, sun-drying, fermenting or repeated steeping in bowls of water before consumption. Cycads are popular horticultural subjects, with specific links with religion (Palm Sundays). Other cycad uses include acting as windbreaks and providing fuelwood. The nitrogen-rich leaves are said to be employed as a fertilizer in rice and potato fields. Ornaments such as flasks, vases and small boxes can also be made from the caudex of this plant.
The objectives of this collection are to:
- acquire a nucleus of parent plants for breeding purposes, especially species from Zimbabwe and Central Africa and those which grow well in Vumba
- make available cycad materials for study, research and aesthetic use
- enhance the status of the Vumba Botanical Garden
- promote all aspects of cycad conservation
The threat to cycads is mainly from man:
- over-collection for use in private gardens and profit making
- ever-dwindling natural habitats
- death of pollination agents through lack of suitable ecological requirements or poisoning by herbicides and other combative chemicals
- genetic contamination through uncontrolled hybridization
- mismanagement of stock specimens, e.g. separation of microsporangiate plants from their opposite sex
The cycad collection at Vumba is still in its infancy. Most cycad specimens were collected in early 1995 and were planted out by December of the same year. This covers 7 of the 11 genera, 2 of the 3 families and 59 of the 185 known species with 5 different unnamed cycad species which need verification. The following have now sprouted new leaves in their new stations: Encephalartos manikensis, E. ferox, E. lehmanii, E. pterogonous, E. cycadifolius, E. eugene-maraisii, Dioon edule, D. mejiae, Zamia furfuracea, Macrozamia fawcettii, M. lucida and Cycas thouarsii. In cone are the following: Encephalartos manikensis (F); E. aplanatus (F), E. alteinsteinii (F), Macrozamia fawcettii (F), Zamia furfuracea (M), Cycas revoluta and Dioon edule var angustifolium (whose sex is yet to be determined). We also have seeds of Ceratozamia robusta, Zamia integrifolia, Encephalartos concinnus, E. manikensis and E. ferox being propagated. Seedlings that have germinated under our direct care are of Encephalartos manikensis, E. transvenosus and Zamia furfuracea. Thus our experience in cycad propagation and cultivation is developing.
Zimbabwe boasts three cycad species, these being Encephalartos manikensis, E. concinnus and E.chimanimaniensis. The E. chimanimaniensis colony used to lie on the border between Zimbabwe and Mozambique. The populations on the Zimbabwean side have been decimated. E. concinnus still exists in the wild on a private farm in the south western part of the country. We have personally visited one of the E. manikensis colonies where I estimated the standing plants to be above six hundred. Signs of vandalism were however, evident.
In so far as consumption of cycad materials by man is concerned, I have had no personal experience except what I have gleaned from the elders residing in the vicinity of the E. manikensis colony, as well as from the literature. During severe drought, the caudex of Encephalartos manikensis is trimmed of roots and leaves, pounded into pulp which is packed in hessian bags. The package is left in water for up to seven days for fermentation to occur. Thereafter the pulp is sun-dried and later ground to produce a powder that is utilised in making dough. The dough is then baked into some kind of bread that sustains the community until they can harvest other crops.
In addition, slides and photographs, ethnobotanical notes and herbarium specimens form an integral part of the project.
The Department of National Parks and Wild Life Management is responsible for the implementation of CITES and monitoring local trade. Current permits are to be more detailed to include a more intensive monitoring mechanism to protect the indigenous flora which is classified into two categories. The first group covers any indigenous vegetation whereas the second deals with, Specially Protected Indigenous Plants which includes cycads, ferns, orchids the raphia palm as well as aloes. Many people have been prosecuted for picking, possession, sale, purchase, transfer or cultivation of the latter group without the relevant permits.