by Piter Kehoma Boll
Today I’m introducing one of the most bizarre plant species in the world. Found in the Namib desert, in Namibia and Angola, the Welwitschia mirabilis, usually simply called welwitschia or tree tumbo in English, is the solely member of the order Welwitschiales, a group of gymnosperms in the division Gnetophyta.
The tree tumbo has a unique appearance. The seedlings have two cotyledons (the original leaves produced by the seed) and later develop two permanent leaves that grow opposite (at right angles) to the cotyledons. These permanent leaves grow continuosly, reaching up to 4 m in length. While growing, the leaves split and fray into several straps and occupy an area of about 8 m in circunference around the plant. The stem is woody and the flowers appear on a central part called crown. The species is dioecious, meaning that male and female flowers appear in different plants. Pollination is usually carried out by insects.
Living up to 2 thousand years, the tree tumbo is a very peculiar desert plant. Its leaves are broad and very large, different from what is the rule in the desert. Its root system is also very shallow, not penetrating deep in the ground. It seems that most of the water used by the plant is captured by the leaves from the morning fog.
Although having a very restrict range, the tree tumbo is not (yet) and endangered plant, as its population is considerably large. However, due to its popularity, some areas attract collectors, and since its growth is so slow, it may eventually become a vulnerable plant.
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Bornmann, C. H. 1972. Welwitschia mirabilis: paradox of the Namib Desert. Edeavour, 31(113):95–99.
Wikipedia. Welwitschia mirabilis. Available at <https://en.wikipedia.org/wiki/Welwitschia>. Access on March 1, 2017.
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