Encephalartos arenarius – Dyer (1956)

Alexandria cycad, Dune cycad (Eng), Duine broodboom (Afr)

Category: Endangered

Description


Encephalartos arenarius stems may be up to 1m tall, but in its habitat the lower part of the stem is usually covered by sand and leaf mold. Smaller plants often appear to have subterranean stems for this reason. The diameter of the stem is 20cm to 30cm but it may be wider at the base. The crown of the stem is covered with light-brown hair, especially before new leaves are formed. Single stems occur, but plants are more usually branched from the base to form clumps with stems of varying height. Taller stems usually lean over to one side.

The attractive leaves of E.arenarius may be 1m to 1.5m long, including a leaf stalk of 15cm to 20cm long. The rachis is recurved at the tip and the leaves are light green when they are young with a slight bloom. Older leaves become darker green in colour and the bloom disappears. In a few, probably dryer, localities a bluish-green form occurs.

The pinnae at the middle of the leaf are 12cm to 16cm long and 2,5cm to 4cm broad. The leaflets have three or four lobes on the lower margin. The upper margin is usually smooth, but may occasionally have one tooth. The lobes are in the same plane as the leaflet or slightly twisted. The lower leaflets have only one or two lobes and are reduced in size to an occasional single prickle. Seedling leaves have three lobes at the tip, with or without a tooth on the upper margin and one or two teeth or lobes or the lower margin. The leaflets overlap in the top part where they are attached to the rachis in the form of a “V”. Lower down they are more widely spaced and more spreading.

Single cones are formed. Mature cones are light green in colour and are borne on a short thick peduncle, 4cm to 8cm long. The male cone is 30cm to 50cm long and 8cm to 15cm in diameter. The scales at the middle of the cone are approximately 3.5cm long and 2.5cm wide. The beak of the scale protrudes approximately 1cm.

The female cone is barrel-shaped, 35cm to 60cm long and 20cm to 30cm in diameter. The scales at the middle of the cone are approximately 7cm long, 5cm broad and 4cm high. The face of the scale is usually four-sided with a slightly wrinkled surface and a beak which protrudes approximately 2cm. The female cone is often pushed down to an almost horizontal position by the formation of new leaves. The sarcotesta is red and shiny and seeds are approximately 5cm long and 2,5cm wide, with a fleshy beak.

Female cone

Male cone

Leaf detail

Distribution & Habitat


E. arenarius occurs in a relatively limited area in the Alexandria district. It typically grows in shade on sand dunes in the coastal forests and scrub bush. The rainfall ranges from 725mm to 875mm per year and occurs throughout the year. No frost occurs and the summers may be hot and fairly dry.

 

Cultivation & Propagation


E.arenarius grows well in cultivation if planted in the right conditions. They should be grown in sandy soil with sufficient leaf mold or compost and should be kept moist. Although they grow in shade in their natural habitat, they tolerate direct sunlight. Growing them in half-shade will prevent the leaves from burning on hot, dry days. Plants must be protected against frost.

Established plants form leaves each year and two sets of leaves per year are common and three sets not unusual. Seedlings are commercially available and grow well. Plants in cultivation cone regularly and artificial pollination is possible. Propagation by seed is easy and suckers can be removed from the parent plant.

 

Notes


In 1953 Dr E.E.A. Gledhill reported the discovery of a colony of unidentified Encephalartos on inland sand dunes near Alexandria. In 1954 Dr R.A. Dyer accompanied Dr Gledhill on an inspection visit to the locality, where he came to the conclusion that a new species had been discovered. Dr Dyer published the new species in the Journal of South African Botany on 31 December 1955. Dr Dyer appropriately named the new species arenarius, meaning “growing in sandy places”.

The only species with which E.arenarius may be confused, and to which it is obviously most closely related, is E.latifrons. The following guidelines may be used to distinguish between them:

  • E.arenarius only occurs in the coastal areas of the Alexandria district and it’s distribution area does not overlap with that of E.latifrons which occurs in the inland Albany and Bathurst districts.
  • The stems of E.arenarius are only up to 1m tall, while E.latifrons may have stems up to 3m tall.
  • The leaves of E.arenarius are lighter green than the shiny dark green leaves of E.latifrons, and may sometimes be bluish-green.
  • The leaflets of E.arenarius are more widely spaced than the interlocking, densely-spaced leaflets of E.latifrons.
  • E.arenarius bears single cones while E.latifrons may have as many as four cones.
  • E.arenarius cones are light green in colour while those of E.latifrons are olive-green or bluish-green.
  • The surfaces of the female cone scales of E.arenarius are relatively smooth compared to the deeply furrowed, wrinkled and pimply surfaces of E. latifrons.
  • There have been reports of plants which appear to be hybrids between E.arenarius and E.altensteinii. E.arenarius and E.latifrons will produce artificial hybrids.

E.arenarius was once fairly numerous in its habitat area. It was threatened even before it was described as a species, however. When Dr Dyer visited the area in 1954, he was told by local farmers that “a large number had been removed for cultivation within recent times”. (Dyer, R.A. : “A new cycad from the Cape Province”.) Numerous plants were also removed to make way for farming activities, especially the establishment of pastures for dairy herds.

The accessibility of the habitat and the relative ease with which plants can be removed from the sandy soil, have made E.arenarius an easy target for destructive collectors. Truckloads of plants were illegally removed with the result that E.arenarius has now become fairly rare in nature.