Euphorbia clivicola
R.A.Dyer

Family : Euphorbiaceae

This is a critically endangered low succulent perennial endemic to the Limpopo Province. It has short, spiny, 4-angled branches arising from an underground system of rhizomes and roots. It can be propagated by means of shoots or seed.

Description
Euphorbia clivicola is a short, spiny perennial succulent with a subterranean root system and a root tuber which is about 150 mm long and 20–30 mm thick and tapers towards the base. Four-angled branches, armed with paired spines are yellowish green, about 20–60 mm long and aggregate into a dense mass above the ground. The flowers are very small and unisexual and are arranged in cup-like structures with yellow, nectar-bearing glands around the rim. These structures are called cyathia (singular: cyathium). They are arranged in groups of three at flowering eyes towards the end of the branches. In each group of three cyathia the central one contains only male flowers and the outer two contain both male and female flowers. Seeds are produced from mid-May to mid-July in a three-chambered fruit capsule with 1 ovule in each locule. Plants produce toxic, milky latex (Smart 1999).

Euphorbia clivicola showing root tuber
Euphorbia clivicola showing root tuber

The family Euphorbiaceae is the sixth largest plant family consisting of over 300 genera and over 8,910 species (Kondamudi et al. 2009). The genus Euphorbia is the largest of the genera and has more than 2,000 species that are found throughout temperate, tropical, and subtropical regions worldwide (Court 2010). South Africa has a large number of endemic euphorbia species.

Euphorbia clivicola showing four-angled branches and paired spines Euphorbia clivicola showing
four-angled branches and paired spines

In African, there are three main types of euphorbias: the tuberculate-stemmed, the pencil- stemmed and the paired-spine species. Tuberculate-stemmed species are almost entirely confined to the Cape Province (Oldfield 1997), while paired-spine euphorbias are found throughout the country with the greatest number of species in Limpopo Province.

Derivation of name
The genus Euphorbia is named after the first-century AD Greek physician Euphorbus who first used the seeds of the plant containing milky latex for medicinal purposes. The specific name clivicola is derived from the Latin word ‘clivus', meaning the slope of a hill, and 'cola' meaning dwelling place.

Distribution and habitat
Euphorbia clivicola occurs in two populations which are about 38 km apart. The one population is situated in the Percy Fyfe Nature Reserve southwest of Polokwane while the other population occurs in an urban area on the outskirts of Polokwane (Pfab & Witkowski 1998). Euphorbia clivicola grows on gentle slopes with northern and north-eastern aspects. The veld type around the plants is classified as sour bushveld derived from white quartzite stones (Dyer 1951).

Conservation status
Euphorbia clivicola is listed on the South African Red List of Threatened Plants as “Critically Endangered” (Pfab et al. 2008).

Population size
The numbers of E. clivicola plants have decreased drastically in the past two decades. In 1986 there were 1,500 individuals in the Percy Fyfe Nature Reserve and 3,000 individuals in the urban area (Fourie 1986). In 1996, the numbers decreased to 165 and 382 in the respective areas (Hilton-Taylor 1996). In 2005, there were 58 plants left in the nature reserve while the plants in the urban area had increased to 651 (D. Engelbrecht, pers. comm.). Last year a survey was done and only ten plants were found in the nature reserve (E.T. Moeng, pers. comm.).

Threats
The plants in the Percy Fyfe Nature Reserve are decreasing due to continuous trampling by antelopes, herbivory by insects such as Protostrophus beetle and poor fire management (Pfab & Witkowski 1998).

The plants in Polokwane occur on the fringes of a growing human settlement. The dumping of building rubble on the plants has lead to a number of losses. Recreational activities such as quad biking also led to the disruption of the growth habit and death of some plants. Illegal waste dumping in the area has resulted in the introduction of rodents that feed on the branches and fruits of the plant (D. Engelbrecht, pers. comm.).

Uses and cultural aspects
The genus Euphorbia is characterized by the toxic, milky latex that the plants exude upon wounding. Animals usually avoid feeding on spurges (plants of the genus Euphorbia). Euphorbia clivicola appears to be palatable, as rodents and rabbits feed on the fruits.The latex of many spurges is traditionally used to stun fish, and to make rubber and wax. In horticulture the latex is also used to root stem cuttings of woody species.

Euphorbia clivicola

Growing Euphorbia clivicola

Euphorbia species can be propagated by seeds but this poses a challenge, as the fruit capsule bursts open when ripe and seeds are scattered over long distances. To prevent loss of seeds, horticulturalists either place nylon stockings around the ripe fruit capsule or they apply a thin layer of glue to the capsule. The collected seeds are sown in pots or trays that contain a combination of fine to medium grain sand and loam soil. It is recommended that the soil should be sterilised in an oven or autoclave for 20 minutes or pre-treated with fungicides to prevent infections. The seeds are sown by pressing them lightly into the soil and covering them with a thin layer of sand, keeping the soil damp but not wet at a temperature of 27–30°C (Hodgkins 2007; Buddenskiek 2009 ).

Plants can also be propagated by cutting shoots and placing them in water jars to form roots and then transferring them into soil. Water should be changed daily. Shoots can also be dipped into rooting powder and planted in soil afterwards. Care should be taken when handling the plants as they have a toxic latex which may cause inflammation of skin and mucous membranes; contact with eye tissue may lead to blindness.

References and further reading

  • Buddenskiek, V.2009. International Euphorbia Society. (Online) Available http://www.euphorbia-internation.org. cultivation/seedhtm (Accessed 22 January 2012).
  • Court, D.2010. Succulent flora of Southern Africa. Struik Nature Publishers. IBSN 9781770075870.
  • Dyer, R.A.1951. Euphorbia clivicola. Bothalia 6: 221.
  • Engelbrecht, D. 2010. Personal communication. University of Limpopo, Department of Biodiversity.
  • Fourie, S.P., 1986. The Transvaal, South African threatened plant program. Biological Conservation 37: 23–42.
  • Hilton-Taylor, C. 1996. Red Data List of southern African plants. Strelitzia 4. South African National Biodiversity Institute, Pretoria.
  • Hodgkins, R.J. 2007. The succulent page. (Online) Available http://www.succulent- plants.com/seed.htm (Accessed 22 January 2012).
  • Kondamudi, R., Murthy, K., Pullaiah, T., 2009. Euphorbiaceae- A critical review on plant tissue culture. Tropical and Subtropical Agro-ecosystems 10: 313–335.
  • Moeng, E.T. 2011. Personal communication. Limpopo Department of Economic Development, Environment and Tourism.
  • Oldfield, S., 1997. Cactus and succulent plants: status and conservation action plan. IUCN/SSC Cactus and Succulent Specialist Group, Switzerland and Cambridge, UK. ISBN 2-8317-0390-5.
  • Pfab, M.F.& Witkowski, E.T.F., 1998. Conservation biology of the critically endangered dwarf succulent plant species, Euphorbia clivicola, endemic to the Northern Province. Report submitted to the Department of Environmental Affairs, Northern Province. 1–11.
  • Pfab, M.F., Matlamela, P.F., Leroy, M. & Von Staden, L. 2008. Euphorbia clivicola R.A.Dyer. National Assessment: Red List of South African Plants version 2011.1. Accessed on 2012/01/25.
  • Smart, R.M. (1999). Conservation biology of Euphorbia clivicola R.A. Dyer, a critically endangered plant. A research report submitted to the Faculty of Science, University of the Witwatersrand. 1–43.

 

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