This Tree may reach 2m high. The Leaves are pinnately compound and up to 90cm long. The dioecious Cones area creamy grey. Seeds have a yellowish fleshy testa and are up to 3 x 2cm.
RSA Tree No. 5.2.
Common names: Olifants River Cycad.
Family Zamiaceae. This is a family of perennial cycads with 8 genera and about 150 species. They are only superficially palm or fern like. The cycad tap Root is soon replaced by lateral roots, which become woody. Cycads have coralloid roots that contain symbiotic cyanobacteria (blue-green algae) that fix atmospheric nitrogen in association with root tissue and produce important amino acids for the plant. Stems are cylindrical and southern African species do not have persistent leaf bases. All are evergreen with pinnately compound Leaves. The leaflets have parallel veins. Unlike other members of the family Zamiaceae, species in the genus Encephalartos have leaflets that lack a central Vein. Stomata are present on the lower surface and may occur above as well. All are dioecious with male and female Cones on separate plants. Female cones disintegrate at maturity releasing the Seeds. All produce poisonous glycosides (cycasins).
Name derivation: Encephalartos – within-head-bread: referring to the starchy bread that can be made from the pith of the inner trunk. lanatus – Latin for woolly – between leaf bases the stem is woolly. The African plants in the genus Encephalartos include about 66 species and there are about 30 species of Encephalartos in southern Africa. The genus Encephalartos includes some of the most primitive living Gymnosperms.
Conservation Status: Near Threatened. 2009. J.S. Donaldson.
Description. This Tree can grow to a height of 2m and has a diameter of up to 30cm. This is relatively narrow. The Stem is woolly between leaf bases – hence the specific name. The many persistent, woody leaf bases provide much of the structural support for the trunk. These surround the stem. More than one stem and Suckers may be present.
Cycads are unique Gymnosperms with pinnately compound Leaves (here the leaflets are arranged along either side of the leaf rachis, the central stalk, like a feather). These leaves are green to bluish green, almost silvery, up to 90cm long and tend to curve backwards. They are strongly keeled and pinnately compound (leaflets are arranged along either side of the leaf rachis – a central stalk). Young leaves are silvery and hairy. Leaflets are not lobed, but do overlap and have clearly visible veins on the lower, slightly lighter, surface. The central leaflets are the largest – up to 140 x 8mm. Leaflets have a powdery bloom and are initially bluish green, becoming green with time. Leaflet size decreases towards the spineless Petiole (leaf stalk) – which is up to 10cm long. The Rachis (main axis bearing flowers or leaflets) is greenish.
The initially creamy yellow Cones change to grey and are usually produced on an annual basis. They are covered with a persistent hairy layer giving the colour. The tree is dioecious (having male and female cones on different plants). The Male cone are reddish, woolly, cylindrical but much narrower and slightly shorter than the female cones. Each cone is up to 30 x 6cm. The barrel shaped Female cones are densely woolly and up to 4 are produced. Each is up to 35 x 15cm. They are situated on a stalk that is up to 2cm long. Seeds are up to 3 x 2cm and have a yellow fleshy testa (this type of seed coat is called a sarcotesta).
Gymnosperms have unenclosed or naked seeds. They have no flowers or fruit and the seeds are often contained in cones. In the Angiosperms (flowering plants), the seeds are enclosed in an ovary. In the Gymnosperms, there are 2 modes of fertilization. In all the Cycads (including Encephalartos) and the single extanct (not extinct) species of Ginkgo (Ginkgo biloba), the male cones produce motile sperms. Whereas, the remaining members of the Gymnosperms all have non-motile sperm with no flagella and are moved along with a pollen tube to the egg.
Distribution & Ecology
This cycad is slow growing and is Endemic (Endemism is the ecological state of a species being unique to a defined geographic location) in South Africa. Plants can be found on sandstone slopes and in sheltered valleys. They occur mainly in the catchment area of the Olifants and Wilge Rivers. The former starts near Bethal – (about 150km east of Johannesburg in Mpumalanga) and Breyten which is the highest point on the watershed between the westward flowing Vaal River system draining into the Atlantic Ocean and the eastward flowing Olifants and Komati River systems which drains into the Indian Ocean after flowing through Mozambique. This Cycad is fire and frost resistant and the dark stem colour may also reflect the passage of fire. Trees are found in deep sandy soil, often in grassland where annual rainfall is in the region of 660-770mm. They occur naturally in Gauteng and Mpumalanga to the East of eMalahleni (Witbank). Altitude range is up to 1 800m. There are only 2 known insects that feed exclusively on the cycad gametophyte. One of these is the long-snouted weevil, Antliarhinus zamiae, which lays its eggs inside the cycad seeds and the hatched larvae devour the seeds. The effect can be devastating – for the trees.
This slow growing plant is drought resistant and frost hardy. It does best with summer rainfall and in moderately sunny positions. The distinction between this plant and that of E. humillis, E. friderici-guilielmi and E. lavifolius is small. It is distinguished from the lattermost by having keeled leaves which end in recurved tips. E. lanatus also has and densely woolly crown. The best means of propagation is by Seeds. Note these seeds may be poisonous. Toxic compounds in plants generally serve in a defence mechanism and may have had an important role in Cycad survival over their long evolutionary history. Take appropriate care when handling seeds and do not eat them. Toxins involved may affect the liver and increase cancer risk.
Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.
Lawrence, G. H. M, 1951. Taxonomy of Vascular Plants, The Macmillan Company, New York. Tenth Printing 1965.
Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.
Schmidt, S. Lotter, M. & McCleland, W. 2002. Trees and Shrubs of Mpumalanga and the Kruger National Park.