African flora

Native to the rainforests of west Kenya and Uganda, the African tulip tree (Spathodea campanulata) will grow up to a height of 24 m/80 ft in any tropical region. It is also known as the fountain tree, the fire tree, or the flame-of-the-forest. These names are references to its brilliant scarlet or orange–red flowers, which resemble tulips in shape.

Giant senecio, Shira Plateau, Tanzania. The Senecio genus comprises shrubs, trees, herbs, and climbers – including groundsel and ragwort – and can be found throughout the world. The plants pictured grow in the Afro-Alpine zone of the East African mountains, at around 3,660 m/12,000 ft.

Lobelia, Shira Plateau, Tanzania. The lobelia family contains over 750 species of flowering plant, native to both hemispheres. They are mostly small annual plants, but the tall tree-lobelias of East Africa grow for about twenty years and flower only once.

Africa has a wide variety of habitats and plants. Some 300 genera are widely distributed throughout the continent and just over 100 of these appear to be confined to Africa. These wide genera are either essentially tropical in character or, like the genus Protea, are predominantly found in southern Africa. Some regions are very rich in species and very highly specialized.

The southern African flora as a whole is one of the most remarkable floristic assemblages in the world, especially that of the Cape, the South African winter-rain region. This tiny area, which on its own comprises an entire floristic realm, is extraordinarily rich in species, with well over 2,500 species of flowering plants. In the Jonkershoek nature reserve no less than 2,000 species have been recorded in an area of 2,000 ha. Many of the plants have been introduced elsewhere and have become well known as garden plants, including many species of Erica (over 600 species are confined to South Africa and most of these to the Cape), Gladiolus species, Pelargonium species, and the parents of the artificial hybrid, Montbretia. The vegetation of the Cape is similar to that of the Mediterranean maquis, being a low scrubland, the fynbos, dominated by members of the family Proteaceae. The only tree, the silver tree Leucadendron argenteum is confined to the humid slopes of Table Mountain.

Other genera characteristic of southern Africa are Mesembryanthemum, Senecio, Helichrysum, and Oxalis. The region is also noted for its succulents, some of which are stem succulents, like the cacti of America, but which here belong to the Euphorbiaceae and the tribe Stapelieae, while others are leaf succulents, usually members of the Crassulaceae. The flora of the Karoo is also highly specialized, displaying remarkable adaptations to moisture stress. Most famous are the ‘stone plants’, like those of the genus Lithops, which resemble pebbles. Haworthia, the plant with a built-in greenhouse and moisture-control, also occurs here.

East Africa Another highly specialized flora is found in the afro-alpine belt (over 3,700 m/12,138 ft above sea level) of the East African mountains. This is the home of the so-called tree-senecios and the giant or tree-lobelias. The tree-senecios look rather like large cabbages on massive trunks, while the tree-lobelias are tall, columnar plants which grow for about 20 years, then flower once and die. These curiosities of the plant kingdom are remarkable on two accounts. Firstly, they show a range of adaptations to the peculiar climatic conditions that prevail in the afro-alpine belt, where every day is like summer and every night like winter. Secondly, they are not only endemic to the East African mountains (although similar Lobelias occur in Latin America), but some of the species are endemic to one mountain only, such as Lobelia keniensis on Mount Kenya and Lobelia dekenii on Mount Kilimanjaro, or to a mountain group. The afro-alpine flora as a whole shows a wide range of adaptations and is estimated to contain some 280 species in 115 genera. It should also be noted that East Africa is the home of one of the world's best-known house and office plants, the African violet, Saintpaulia ionanthe.

Turning from these highly specialized floras to the more general vegetation of Africa, it is obviously important to look at the floristic structure of the African rainforest formation. Although poorer in species than its Latin American and Asian counterparts, the formation is nevertheless rich in species. The dominant trees belong to some seven families, namely the Leguminosae, Euphorbiaceae, Moraceae, Sterculiaceae, Meliaceae, Sapotaceae, and Ulmaceae.

West Africa The rainforests in West Africa harbour a wide range of important timber-producing species, including Celtis species, Chlorophora excelsa, Khaya species, Mansonisa altissima, Piptadeniastrum africanum, Terminalia superba, and Triplochiton scleroxylon. Among other plants of economic importance, the West African rainforest region also boasts Coffea liberica and the oil palm Elaeis guineensis, as well as species of more local importance, like the native rubber plants, Funtumia elastica and Landolphia owariensis.

The African savannahs contain a number of trees of economic value. Good examples of these are the mahogany bean Afzelia africana, shea butter Butyrospermum paradoxum, African locust bean Parkia clappertoniana, and black plum Vitex doniana. A famous tree of the dry savannahs and thorn-scrub is the baobab, Adansonia digitata. This tree can store as much as 120,000 litres of water in its soft wood. The most important economic plant coming from the Saharo-Arabian desert region is the date palm Phoenix dactylifera, while Ethiopia has provided the world with one of its most important beverages, coffee Coffea arabica.

The Namib desert in southwestern Africa is famous for its ephemeral species of Mesembryanthemum, but most of all for the remarkable endemic gymnosperm welwitschia Welwitschia mirabilis. This unique plant has only two leaves, which have an unlimited capacity for growth, even though the plant may persist for well over 100 years. One plant, with a diameter of 1.5 m/5 ft, was found to be between 500 and 600 years old when radio-carbon dated. If water is short, the leaves dry up completely to the base, but as soon as more favourable conditions return, the leaves are regenerated.

Finally, it is necessary to comment on the important flora of the Madagascar region, including the Comoros, Aldabra Islands, the Seychelles, and the Mascarenes. Although seriously disturbed by the actions of humans, the region possesses well over 400 endemic genera, including Stephanotis.