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Tree of the Week: The Welwitschia: Small, old, odd

October 5, 2009 |  9:18 am

The Welwitschia – Welwitschia mirabilis

The Welwitschia (well-WIT-shia) may well be the oddest tree in the world. It produces only two, strap-shaped leaves, which for its 500- to 2,000-year-long life keep on growing from the base and dying from the top. Its trunk rises only a foot or so above the soil surface and stays there, but keeps getting wider every year.

While it is cone bearing, it does not completely belong in one of the two main groups of plants -- the gymnosperms (cone-bearing trees with naked seeds, softwoods), or the angiosperms (flowering trees, with covered seeds, hardwoods) -- but has characteristics of both.

Berk_bot_gdn_8.09_055 The Welwitschia originated in the extremely harsh, dry and windy environment of the Namib Desert of Angola and Namibia in southwestern Africa. There, the mixing of cold ocean current with hot desert air produces dense fog every morning. Microscopic leaf hairs take in most of the plant’s water from the morning fog. Its stomata, or leaf holes, close in daytime to prevent exhaling moist air, but open at night and in the cooler hours, during which time they inhale and store the air’s carbon dioxide for processing during the heat of the day. Our Southland climate is hospitable to many trees from all over the world, but does not duplicate fog desert conditions, so you will not see the tree outdoors in Los Angeles. However, many people grow it indoors, which is not that hard to do, and you may find it in botanical gardens.

The tree grows ever so slowly until it resembles a huge woody carrot with a grayish-brown flattened top on a short, fibrous above-ground stem with corrugated bark. The leaves are implanted around the top of the trunk. The tallest one reaches 5 feet; the fattest trunk is 10 feet wide. Roots, including the thick taproot, may go 90 feet down. There are no branches. The thick leathery evergreen leaves keep growing from the base, but split lengthwise and then partially curl and bunch up, so that there appear to be many more than 2. The leaves channel the fog to the roots. Male and female flowers are borne at the top of the trunk, on different plants. The larger female cones are blue-green, the smaller and less cone-like males are salmon-colored, small and oblong. Unlike other cone-bearing plants, they depend on insects for fertilization.

Austrian botanist and medical doctor Friedrich Welwitsch, who was employed by the Portuguese government, "discovered" the plant in 1859. Its descriptive South African name is tweeblaarkanniedood (two leaves cannot die). Oyanga, the local Herero name, means onion of the desert and is said to refer to the tasty stem.

--Pieter Severynen

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Photo: A relatively young plant with a female cone. Credit: Pieter Severynen

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