Welwitschia Hooker fil. 1863 (Tumbo)
Named for: Friedrich Welwitsch, Austrian botanist.
Welwitschia mirabilis seedling
The type species, Welwitschia mirabilis, from the Namib desert of South-West Africa (Angola, Namibia) has a short, central, unbranched, woody caudex up to 3ft in diameter from which grows a single pair of persistent tough, leathery leaves. These grow longer with time, from the meristem at their junction with the caudex. The ends of the leaves fray in the desert sandstorms and split lengthwise along the leaf veins, but otherwise are of indefinite length. No other permanent leaves are ever produced although a pair of short lived cotyledons grow after germination. Splitting of the permanent leaves may present the appearance of multiple leaves. A long tapering taproot extracts scarce moisture from deep under the plant.
The plants are dioecious, bearing inflorescences with clusters of male and female cones on separate plants. Pollen is distributed by wind and by a variety of insects that feed on it. Individual plants are slow growing and may be thousands of years old. They are sustained by dense fogs as rain is minimal, and absorb moisture through stomata on the large leaf surface. These plants are not truly succulent but certainly caudiciform.