Welwitschia mirabilis

Welwitschia mirabilis, sometimes commonly called the tree tumbo, in Herero onyanga (onion of the desert) and in Afrikaans the tweeblaarkanniedood (two-leaf-cannot-die), has been given an Afrikaans name although the plant does not grow in nature in South Africa. South Africans are often intrigued by desert plants and succulents. This awareness, curiosity and horticultural bent result from so much of the country's interior being arid, and the natural world unitary with gradual changes over distance. Southern Africa is famous for the huge diversity of xerophytes endemic here; plants adapted for survival in dry environments where moisture availability is low.

So, when such a strange plant grows close to the border, the local plant aficionados will take an interest. W. mirabilis grows naturally only in the Namib Desert of Namibia and southern Angola, especially in the Kaokoveld region. Namibia is a next door neighbour to South Africa blessed by unique natural beauty in the many forms of life adaptations in its demanding aridity. Afrikaans is also spoken there, so the Afrikaans common name could have been given by Namibians.

The tweeblaarkanniedood crowns the botanical wonders found in Namibia for many people. It lives in some of the earth’s most extreme hyper-arid conditions. The plants reach ages from 500 to 2000 years. Indeed an unusual lifespan for any plant under any conditions, barring some of the big tree species like Podocarpus or Sequoia. These trees also belong to ancient conifer families as Welwitschia does, but possibly in the group that bridges to flowering plants. W. mirabilis is a spreading, woody, evergreen reaching heights to 2 m and double that in width.

Some Welwitschia features resemble succulents, trees or caudiciform plants, while overall it fits into none of them. Botanically the species is in its own separate genus, also the sole member of its family, the Welwitschiaceae that houses the monotypic genus. This is truly one of the most unusual plants on earth, a living fossil from Jurassic times.

In its young days as a species, maybe 80 million years ago, W. mirabilis may have been eaten by dinosaurs, as its leaves are eaten today by some animals in the Namibian and Angolan coastal desert, including rhino, elephant, oryx and zebra, also horses. They chew the leaves and spit out the fibres. Some indigenous people eat the cores of fresh female cones raw or baking them in hot ashes. There's not too much edible organic material in some of the desert parts where these plants grow, so beggars can't be choosers and ingenuity grows with evolution.

This environment is known for its heavy fog, where air cooled by the cold Benguela Current of the west coast meets the hot air from the Namib Desert. This generates fog equivalent to an annual rainfall of 60 mm. Welwitschia copes just fine here, doing well in gravelly plains and dry riverbeds but coping more widely. The metres long leaves of W. mirabilis absorb moisture from both surfaces. In addition, the big Welwitschia taproots reach down to 30 m into the sand and sandy soil, gaining additional moisture from subterranean sources (Mannheimer and Curtis, (Eds.), 2009; iNaturalist; Wikipedia; www.namibweb.com; https://pza.sanbi.org).