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Welwitschia mirabilis (Tree Tumbo, Onion of the Desert (Onyanga) or Welwitschia)

Michael's Opinion

A very unusual plant growing in one the harshest environments on earth with a life expectancy of up to 1500 years. Growing in a climate with little to no rain the plant can sustain itself from the moisture in ocean fogs which it is estimated may at times equal 50 mm of precipitation.

Botanical Information

Family	Welwitschiaceae
Genus	Welwitschia
Species	mirabilis
Category	Perennials, Tropicals
Origin	It is found growing in a narrow long band following the Kuiseb River, from the Namib desert in Namibia to the Mossamedes desert in Angola and seldom more than 150 km from the coast. The plant was discovered by an Austrian doctor/explorer/botanist named Frederich Welwitsch in the Namib Desert in 1859 . Welwitsch, in 1862 then sent material on to Sir Joseph Hooker who was the Director of Kew: Hooker named the plant after him.

Details

USDA Hardiness Zone	9
USDA Hardiness Ref.
Canada Hardiness Ref.
RHS Hardiness Ref.
Height	2 m
Spread	4 m
Growth	Slow
Flowering Period	July, August, September, October, November

Description and Growing Information

General Description	The core of the plant can be cooked in hot ashes and eaten.
Shape	Two, large, coarse, strap-like leaves originating from a central caudex.
Cultivation	Grow in a clay sewer pipe, upended (see image) to accommodate the extended tap root; water very sparingly.
Pests	Rhino and antelope may chew the leaves, often rejecting the coarse fibre, however harm to the plant seldom occurs since the meristematic tissue is rarely destroyed.
Notable Specimens	The largest recorded Welwitschia can be found in the Messum Mountains, Namibia and has reached a height of 1.8 m.
Habitat	In the dry deserts of Namibia and Angola where coastal fogs are present often long dry watercourses and occasionally on elevated slopes or cliffs.
Leaf Description	Two broad, strap-like, evergreen leaves are often shredded by desert winds are attached to a woody caudex. These leaves may each reach up to 2 m in length and like grass leaves have their meristematic tips at the base and continue to grow even though the leaf tips may be abraded by desert sands. The leaves are CAM photosynthetic.
Flower Description	The plant is a gymnosperm. The male flower has a sterile modified pistil that exudes nectar with up to a 50% sugar content from a modified pistil-like structure. It is suspected that the plant may be pollinated by wasps because of the rich nectar produced and the limited amount of pollen (most gynosperms are wind pollinated). The female has exposed stigma's and produces minimal amounts of the nectar.
Fruit Description	The plants are dioecious. The male cones are salmon coloured, small and oblong in shape while the female cones are larger, blue-green in colour and have a distinct taper to them. The female cones disintegrate to disperse small seeds ( 36 x 25 mm ) with a papery wing attached. The seeds seldom germinate unless there are several days of consistent rain which is rare, hence why many plants in a colony are the same age. Most seeds are lost to fungal infections and desert wildlife.

Photographs

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