Botanic Notables: Welwitschia Mirabilis

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Botanic Notables: Welwitschia Mirabilis

July 28, 2011
03:40pm
Photo by: Thomas Schoch

Half-buried in the far flung sands of the Namib Desert, in southern Africa, the Welwitschia mirabilis is a patient exile, and beloved among botanists who seek the very old and the very strange. The oldest individuals have been dated at almost 2,000 years old—among the oldest organisms on earth. And the gymnosperm is considered a living fossil, not for its superlative age, but for a structure (in this case, a bizarre one) that has remained the same for as long as the species has endured—for over 100 million years. 

Its weird appearance is perhaps most expected in the extreme desert climate, but, unlike other desert plants, with short, succulent leaves designed to minimize water loss, the Welwitschia instead has two long, broad, thin leaves that grow up to ten feet in length—the longest of any known desert plant. Papers published on the extraordinary plant have been titled "Welwitschia—Paradox of a Parched Paradise" and "Voyage into the impossible—I meet Welwitschia." And it is unique. In so many millennia of botanic record, the Welwitschia has known no imitators.

Ulenhorst
Photo: Ulenhorst/
Flickr 

It was first discovered in 1859 by Dr. Friedrich Welwitsch, the foremost collector of African plants. When he saw the isolated population sprawling across the barren landscape, he "could do nothing but kneel down on the burning soil and gaze at it, half in fear lest a touch should prove it a figment of the imagination." And botanists since haven't really known what to make of the plant. It grows naturally in isolated communities in just one area of the world, an arid swath of land of about seven hundred fifty mies along the west coast of southern Africa, between rivers in Angola and Namibia. Here, annual rain is scarce—one inch at best, and sometimes none at all. Welwitschia has thus evolved to absorb the coastal fog (only two inches or so a year). Its long, leathery leaves are covered in tiny pores (stomata), which remain open through the night as the fogs rolls over. When the hot sun burns through in the morning, the stomata will close. 

Namib-Naukluft-NP
Photo: Namib-Naukluft-NP

Albeit thus adapted, the Welwitschia is anomaly in the desert—it isn't a typical succulent or a cactus, and neither a shrub nor a bush. It has been named a dwarf tree, for lack of a tidy taxonomical classification. Measuring about 20 inches tall, a short woody trunk peeks above the sand, while a sturdy root digs eight feet into the ground, tapping into traces of water below. Most remarkable of all are the leaves. There are only two—long, sprawling arms that curl across the sand. Unlike most plants, which grow by adding cells at the tips, Welwitschia leaves grow like grasses, lengthening from a meristem at the base. And so, while the tips will age, brown, and die, the leaves continue to grow—slowly, about four to six inches per year. As the years, centuries, and ultimately millennia pass, the desert winds and sands shred the leaves into thick ribbons. This gives it the appearance of "a stranded octopus on the bare desert surface." Tattered and torn, submerged in the sand, it looks quite dead: a fish—or plant—out of water. 

The plant can produce up to 10,000 seeds, but only ten of these are likely to reach maturity. At least 25 mm of rain must fall for the seed to germinate—a rarity in the Namib. And it is difficult to grow in cultivation. Some horticulturalists have succeeded (and some recommend growing the plant in a drain pipe, to accommodate the long tap root), among them botanists at Kew. It was here that the Welwitschia mirabilis was first named, when specimens from Dr. Welwitsch's expedition were sent to the Garden. In the first detailed scientific description of the plant, Joseph D. Hooker, Director of the Royal Botanic Gardens, wrote "It is out of the question the most wonderful plant ever brought to this country, and the very ugliest." 

Ugly, wonderful, and the symbol of a nation—the Welwitschia is featured on the Namibia's coat of arms (below), where it represents survival and fortitude. 

Namibia coat of arms

Namibia's coat of arms from 1961-1990, featuring Welwitcshia (below the shield).