Encephalartos arenarius: the dune cycad and its blue form

Introduction

Encephalartos arenarius is a medium-sized, multi-stemmed, subterranean  plant about 1-2 m high. It grows well in semi-shade but can tolerate full sun as well. There are two distinct forms of E. arenarius, the green form and the rare blue form.

Description

Encephalartos arenarius is a multi-stemmed cycad with a lead stem of 1-2 m long and is 200-300 mm in diameter. The lead stem often lies on the ground covered in sand and leaf mould.

There are often a number of basal suckers competing for the lead. The leaves are 1.0-1.5 m long, dull green, and the leaf stalk recurves sharply at the tip. A blue-leaved form occurs in certain localities.

Female cones are normally solitary, barrel-shaped, 500-600 x 250-300 mm, and light green when mature. The cone scale opens for 5 to10 days in April to May.

The male cones, 1 to 3 in number, 300-500 x 80-150 mm, are light green when mature.

The seed is shiny red when mature.

Conservation status

Much of the coastal Dune Forest in and around Alexandria has been cleared and lost to pastures. This has resulted in Encephalartos arenarius losing its habitat. As it occurs in dune sand, it is easily removed by poachers. It is classified as Endangered (Donaldson 2003).

All South African cycads are classified under Appendix I of the CITES Convention. To own a cycad you require a permit.

Distribution and habitat

Encephalartos arenarius is endemic to the Coastal Dune Forest in the Eastern Cape, South Africa, in the Alexandria area. Some of its common companions in the coastal dune forest include: Apodytes dimidiata , Atalaya capensis, Carissa bispinosa , Dipcadi brevifolium, Euclea natalensis, Gasteria acinacifolia , Gymnosporia capitata, Mimusops caffra , Mystroxylon aethiopicum , Olea europaea subsp. africana , Searsia ( = Rhus ) natalensis, Schotia afra , Sterculia alexandri and Zanthoxylum capense.

Derivation of name and history

Encephalartos is a Greek word meaning 'bread in head' and refers to the floury, starch-like material in the trunks of some species which is used as famine food by local native tribes. The specific name arenarius means growing in sandy places, referring to the habitat. It is often confused with the taller E. latifrons with shiny green leaves, and sometimes also with the broad-leaved E. ferox.

Ecology

Most cycad seeds are commonly attacked by the Curculionid weevil ( Antliarhinus zamiae ).

Growing this species

As noted in other cycad species, Encephalartos arenarius is easily grown from seed. Since cycad seeds are toxic to humans, one should use gloves when handling or cleaning them.

Hand-pollination is necessary for a successful seed harvest in cultivation. Collect pollen as soon as it starts shedding. If a slight tapping of the male cone sheds pollen, then the cone is ready to be harvested; store pollen at -15ºC for best results. The female cone scales have to be monitored to check if they are open. The window of the scale opening varies with individual plants, from three days to two weeks. The wet method, using distilled water in a syringe, has given us a good pollination rate at Kirstenbosh.

After female cones have been collected, the seeds are left to mature for a year before sowing at the beginning of summer. For best results, sow seeds in river sand on a heated bench at 24-28ºC. Germination should start three weeks after sowing though some will take longer. It is easily transplanted and can also be propagated from suckers.

Leaves and cones are prone to scale and mealy bug. The gall-midge also attacks young leaves. At Kirstenbosch in spring, we apply a mixture of 3:1:5 bone meal to each plant. During the year we regularly feed the plant with a generous layer of compost.