The porkbush or spekboom is an attractive, evergreen succulent shrub or small tree that can reach 2 - 5 m in height, although usually around 1.5 - 2m in a garden situation. It has has small, round, succulent leaves and red stems. Small, star-shaped, pink flowers are borne en masse from late winter to spring.

It is found in warm situations on rocky slopes and dry river valleys. It occurs on the eastern areas of the country from the Eastern Cape northwards into KwaZulu-Natal, Swaziland, Mpumalanga and the Northern Province in rocky areas of dry succulent karoo scrub, thicket and bushveld.

The name Portulacaria is composed of Portulaca + aria suggesting a similarity to that genus. The word afra refers to the fact that the plant occurs in Africa.

Interesting ecology has been observed with this plant in the Eastern Cape where it forms part of the diet of the Addo elephants in the Addo National Park. Elephants eat the plant from the top downwards allowing the plant to spread itself vegetatively by spreading horizontal branches at ground level. Outside the park the same plants are eaten by goats who eat the plant from ground level upwards preventing the plant from spreading vegetatively. Consequently these plants must rely solely on seed to proliferate the species which often proves difficult in such a dry climate. As a result is was observed that inside the park where the plant is subjected to browsing by elephants, Portulacaria afra survives and spreads successfully, whereas outside the park the plant is becoming sparse as a result of overgrazing and poor regeneration.

The leaves of the porkbush can be eaten and have a sour or tart flavour. This plant is heavily browsed by game and domestic stock and highly favoured by tortoises. Portulacaria afra has also been indicated as a soil binder for preventing soil erosion.

A very interesting mistletoe, Viscum crassulae, parasitizes this plant. The foliage of this mistletoe is hard and rough in contrast to the soft and smooth leaves of the porkbush.

Growing Portulacaria afra

Spekboom or porkbush is usually propagated from cuttings as the seed is not often available. Cuttings or truncheons strike root easily and can even be planted directly into the ground where they are to be grown. Alternatively cuttings can be taken in the normal fashion and allowed to dry out for a day or two in a cool dry place and then planted in washed river sand and kept in a shady position until they are rooted and ready to be planted out. Cuttings root quickly and can usually be planted out after four to six weeks.

Portulacaria afra can be used as a screen or even a clipped hedge. It also makes a handsome and hardy bonsai. Various different forms are found in cultivation most of which originate from the Karoo Desert National Botanical Garden in South Africa. These forms include a prostrate low growing ground cover, a shrubby form with small round foliage which turns an attractive yellow in full sun, as well as a slow growing variegated form which is well suited to pot culture. The mass of pink flowers are a rich scource of nectar for many insects, which in turn attract insectivorous birds.

This versatile plant can be used in full sun or semi-shade in dry areas or even in well-watered flowerbeds. It tolerates a moderate degree of frost, especially when mature. It is also used as a rootstock for grafting the closely related but more difficult to grow Namaqua porkbush, Portulacaria armiana (previously Ceraria namaquensis) , which cannot tolerate water around its roots as it comes from very dry areas.

Portulacaria afra belongs to a large and widespread family which includes the popular portulaca which is often sold in garden centres and grown in domestic gardens as an annual for summer colour, although it is not a South African species.

References:

• Arnold, T.H. & De Wet, B.C. (Eds) 1993. Plants of southern Africa: names and distribution. Memoirs of the botanical Survey of South Africa No 62. National Botanical Institute: Pretoria.
• Jackson. W.P. U. 1990. Origins and meanings of names of South African plant genera.UCT Ecolab: Capetown.
• Joffe, P. 1993 The Gardeners Guide to South African Plants. Tafelberg Publishers Limited: Capetown.
• Joffe, P. 2001.Creative Gardening with Indigenous Plants, a South African guide.
  Briza Publications: Pretoria.
• Pooley. E 1993. The complete field guide to Trees of Natal, Zululand & Transkei. Natal FloraPublications Trust: Durban.
• Stern, W.T. 1983. Botanical Latin - New edition. David & Charles inc : USA.
• Stern, W.T. 1996. Stern's Dictionary of Plant Names for Gardeners. Cassel : London.
• Van Wyk, B., Van Outdshoorn, B., Gerike, N. 1997. Medicinal Plants of South Africa. Briza Publications : Pretoria.
• Van Wyk, B. & ., Gerike, N. 2000. Peoples Plants. Briza Publications : Pretoria.

Andrew Hankey
Witwatersarnd NBG
January 2002