Dog's ears (Cotyledon orbiculata)
Facts
| Also known as: | pig's ear |
|---|
| Kingdom | Plantae |
|---|---|
| Phylum | Magnoliophyta |
| Class | Magnoliopsida |
| Order | Rosales |
| Family | Crassulaceae |
| Genus | Cotyledon (1) |
| Size |
Height: up to 1 m (2) |
Status
Variety Cotyledon orbiculata oblonga is classified as Lower Risk / Least Concern (LR/lc) in Swaziland on the Southern African Plant Red Data Lists (3). Variety Cotyledon orbiculata flanaganii is classified as Near Threatened (NT) on the Interim Red Data List of South African Plant Taxa (4).
Description
The dog's ears plant, well known to many gardeners, has handsome greyish-green leaves, with a red or pale margin (2) (5). The leaves are thick and succulent, and vary in shape from flat and rounded to almost finger-like (5). The flowers of this shrub, which hang down from the stem, are tubular structures with petals that curve out at the tip (2) (5). These bell-like flowers vary in colour, and may be deep red, pale orange or pink (6). The tall stems that bear the flowers were once used as flutes by early hunters, to mimic the call of a young klipspringer to lure adults within range of their arrows (5).
Range
This species has an extensive distribution, from south-western Angola and Namibia to South Africa. In South Africa it occurs from the Cape Peninsula across the southern Karoo and Free State into the eastern provinces (6).
Biology
The vividly coloured flowers of the dog's ears, which appear in September until December (2), advertise the plant to birds and bees, which flit from flower to flower as they feed on the rich nectar (7). Pollination is believed to be carried out by sunbirds (8), a group of birds with narrow, pointed, downward curving bills (9), suited to probing flowers for nectar.
While light is essential for plants, excess light can be damaging. Under the bright southern African sun, the dog's ears plant has evolved a mechanism to protect itself against damaging excess light. The leaves produce wax that reduces absorption by up to 50 percent, by increasing the reflective properties of the leaves (10). The wax produced by the leaf also helps prevent uncontrollable water loss (11), an important measure for plants growing in warm, dry conditions.
Dog's ears plants also have properties which make them valued by humans. The succulent leaves of the dog's ears are used medicinally, for the treatment of warts and abscesses (8), and when heated, the leaves form a substance used to treat boils and inflammations, particularly earache (7). Surprisingly however, animals that graze on this seemingly innocent plant may suffer from cramps, resulting occasionally in death (5).
Threats
While one variety of dog's ears (Cotyledon orbiculata var. flanaganii) is classified as Near Threatened on the Interim Red Data List of South African Plant Taxa (4), there is, at present, no information indicating what threats this species it may face. It is apparently, in some areas, a widespread and common species (3).
Conservation
At present, there are no specific conservation measures in place for this species. However, even if threatened in the wild, dog's ears are a frequently cultivated species (8), and these populations will act as an insurance against this species extinction.
| Shell South Africa is working with FFI and the Flower Valley Conservation Trust (FVCT) to help conserve part of the Cape Floral Kingdom, the world's most botanically rich habitat. |  |
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Further Information
Authentication
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Pollination: The transfer of pollen grains from the anther (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.
Variety: In taxonomy, (the science of classifying organisms), variety is the rank below subspecies. Members of a variety differ from others of the same species in relatively minor ways.
References
- Heywood, V.H. (1978) Flowering Plants of the World. Oxford University Press, Oxford.
- Goldblatt, P. and Manning, J. (2000) Cape Plants: A Conspectus of the Cape Flora of South Africa. National Botanical Institute of South Africa, Pretoria .
- Golding, J.S. (2002) Southern African Plant Red Data Lists. Southern African Botanical Diversity Network Report No. 14. SABONET, Pretoria.
- Threatened Species Programme. (2007) Interim Red Data List of South African Plant Taxa. South African National Biodiversity Institute, Pretoria, South Africa. Available at:
http://www.sanbi.org/biodiversity/reddata.htm - Paterson-Jones, C. and Manning, J. (2007) Ecoguide Fynbos. Briza Publications, Pretoria, South Africa.
- Court, D. (2000) Succulent Flora of Southern Africa. A.A. Balkema, Rotterdam, Netherlands.
- PlantZAfrica (February, 2008)
http://www.plantzafrica.com/plantcd/cotyledorbic.htm - Eggli, U. (2003) Illustrated Handbook of Succulent Plants: Crassulaceae. Springer-Verlag, Berlin, Germany.
- Allaby, M. (1998) Dictionary of Plant Science. Oxford University Press, Oxford.
- Robinson, S.A. (2001) Plant Light Stress. In: Encyclopedia of Life Sciences. John Wiley and Sons, New York.
- Hamilton, R.J. (2004) Plant Waxes. In: Encyclopedia of Life Sciences. John Wiley and Sons, New York.
