Earth Words: Conservatory Chronicles: Just Two Leaves on This Conifer

The welwitschia is coning in the arid house of the conservatory. If that sounds like a ceremony involving some kind of dark magic, no need to worry. Welwitschia mirabilis, otherwise known as the tree tumbo (its Angolan name), is actually a plant found in arid regions of Namibia and Angola.

Welwitschia mirabilis in Namibian desert (Image: Andrew McRobb, RBG Kew)

Bearing a species name that sounds like a miracle, welwitschia is named after the Austrian botanist Friedrich Welwitsch, who discovered it in 1859. Welwitsch saw the plant in the Namibian desert and reportedly fell to his knees, experiencing a mixture of awe and fear, “lest a touch should prove it a figment of the imagination,” according to the Kew Royal Botanic Garden website.

Another botanist, Thomas Hooker, proposed the botanical name to honor Welwitsch (genus) and mirabilis (species), the species name referring to its extraordinary, wondrous appearance. Though it looks somewhat like a bedraggled or shriveled green ribbon, the tree tumbo is a conifer that is dioecious, meaning there are male or female plants. Welwitschia has only two leaves, which grow out from its base. There are individual welwitschia in the wild thought to be 1,000 years old.

In times of drought mammals such as oryx, springbok, the endangered Hartmann’s zebra, and the critically endangered black rhino chew on tree timbo leaves for moisture, the Kew website states. Reptiles use the shade it throws to shelter themselves from the hot sun.

Ecologically welwitschia is highly specialized. It grows under conditions where it receives regular fog that provides moisture, and it has a deep taproot to reach moisture in the desert. The IUCN (International Union for Conservation of Nature) rates this species as “near threatened.” (The IUCN states that 1 in 5 species of plants in the world are threatened with extinction.)

Recently scientists have discovered a fungal pathogen that infects the female cones; the fungus subsequently reduces seed viability.

Check out this very unusual desert-dwelling plant in the arid house of the conservatory at Matthaei Botanical Gardens!

The conservatory is awash in bloom, by the way. (Remember the welwitschia is a conifer so it doesn’t count!)

Look for these plants in bloom:

Rangoon creeper (Quisiqualis indica) - on the east balcony of the tropical house.