Bitter aloe  (Aloe ferox)

Classified as Least Concern (LC) on the Interim Red Data List of South African Plant Taxa (3), and listed on Appendix II of CITES (1).

The bitter aloe is most famous for its medicinal qualities (4), provided by the golden-brown sap of the leaves (5). The long, tapering leaves are green, sometimes with a slightly blue or reddish tinge (4), and bear sharp, brown teeth on the margins, and sometimes also on the surface of the leaf. Indeed, the scientific name of this species alludes to the prickly leaves, as ferox means ‘fierce’ in Latin (5). The leaves are arranged in a rosette, and as the leaves age and die, they remain attached to the plant, forming a ‘petticoat’ of dried leaves around the base of the stem (4). The flowers of the bitter aloe vary in colour from red to orange and yellow, and occasionally white (6), and are borne on spike-like heads (4).

Occurs in South Africa, ranging from the southern Western Cape, east to southern KwaZulu-Natal, and north into Lesotho and the Free State (6).

The bitter aloe inhabits rocky, stony slopes and flats (2) (5).

The striking flowers of the bitter aloe are seen from May to June in coastal areas and from July until November in inland regions (6). Both birds and honey-bees play a role in the pollination of the bitter aloe. The orange-reddish flowers attract birds that alight on the flowers or a nearby branch, and probe individual flowers for nectar. In doing so, they cover their head, throat and breast with pollen, before moving to another cluster of flowers or a new plant. While nectar is the chief reward for birds, bees are rewarded by pollen, which they remove from the anthers. By visiting the plant, many birds and bees carry out an essential service for the bitter aloe, but not all visitors are beneficial; the streakyheaded canary (Seriunus gularis) is a destructive forager that stands on top of the flower cluster while it removes flowers in search of nectar (7).

While the bitter aloe is not globally threatened with extinction, this species has become extinct in several localities in Lesotho, where harvesting and urban expansion continue to pose a threat to remaining populations (8). The bitter aloe is an important medicinal plant that has been harvested for over 200 years (4) (5), with the bitter yellow sap from the leaves used to produce ointments to heal burns and sunburn (6), and to make a purgative drug known as Cape Aloe (5). The leaves used for this purpose are usually harvested in small, sustainable quantities (8).

The bitter aloe is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), so that any international trade in this species should be carefully monitored to ensure it is compatible with the species’ survival (1). The bitter aloe also occurs in a number of protected areas, including those within the Cape Floral Kingdom, an area of incredible plant diversity in south-western South Africa (9).

For further information on conservation in the Cape Floral Kingdom see:

• Wild Cape Nature Trust:
  www.wildcape.org