Welwitschia mirabilis - Cactus Club

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Welwitschia mirabilis

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by Bruce Brethauer


      Welwitschia mirabilis is one of the most curious and bizarre plants of the plant kingdom; in the course of its very long lifetime (by some accounts the oldest plants may live to about 2000 years), it will only produce two mature leaves, which lengthen seasonally as the plant grows. In established plants in habitat, the leaves will eventually become quite long (sometimes in excess of 20 feet), becoming split and tattered towards their ends. Eventually, the leaf tips die back and break away as the plant grows, limiting their ultimate length. The leaves are thick and quite tough, some authorities report that they are leathery, but in the few mature plants which I have examined, the leaves were much tougher, more like cardboard or wood, (very similar to the leaves of the "Cardboard Palm", but even tougher).

   While not generally regarded as a succulent plant, the roots of this species can be massive, and almost certainly can serve as a water reserve in times of drought. These roots are variable, in some populations, they may be beet-shaped to nearly spherical, while other populations typically produce long, carrot shaped roots reputedly growing to lengths of 70 feet or possibly more - in both cases the root diameter can reach 4 feet or more.

   The stems are quite short, shaped more or less like an inverted cone, and are hollow: in very old plants, these reminiscent of a hollow tree stump, with the two leaves growing on the ridges. In most plants, these are fairly short, usually less than 2 feet in height, but in one of the largest plants, the stem is over 5 feet tall.

   This species is dioecious, with male and female flowers being produced on different plants: the male cones produce pollen, and a structure which produces a nectar; the female cones ultimately produce seed, and also exude a very sweet nectar (with approximately 50% sugar content). Unlike most other cone bearing plants (which are typically wind pollinated) Welwitschia mirabilis appears to pollinated by insects - probably wasps or beetles.

   Plants grow in isolated communities in the Namib Desert within 90 miles of the Atlantic coast along a 620 mile long strip from southern Angola through north-western Namibia, a region which falls within a costal fog belt which provides a significant amount of moisture for these plants (estimated to be the equivalent of 2 inches of rain). This species is adapted to very specific habitats, and even though they may occur in very arid regions, plants may require a steady supply of moisture during their growing season - so plants will typically grow in areas with particularly dense costal fogs, dry river beds, and rocky outcrops. While populations may be isolated, their numbers may be locally abundant: It is also widely distributed through a very large range, therefore, this species is not considered threatened or endangered; its numbers are still very good.

   This is not a common plant in cultivation: ultimately, the large size of the plant, and its huge taproot will make it unsuitable for most collections. Even so, seeds and seedlings are becoming increasingly available through specialist mail order, and online nurseries: seedlings can be maintained for many years before they grow to unmanageable sizes, so at least for a time, it is possible to grow one of nature's great curiosities in our home collections. It is essential to provide a gritty/sandy mineral based soil; even as a seedling, this species will produce a substantial taproot, and will require a particularly deep pot to accommodate this. As the plant grows larger, I have seen growers use chimney liners, and drainage tiles to provide a very long pot for a very long tap root. As a seedling, this species will require evenly moist soils through the greater portion of the summer growing season - one source specifically suggests a weekly watering at this time, with somewhat drier conditions during its winter dormancy (remember that this is not a succulent plant, and has very few water reserves in its tissues as a seedling). While most of the initial growth will be in the roots, the stem will slowly enlarge, and the leaves will lengthen. This species is capable of very fast growth, a plant grown from seed at Kirstenbosch, flowered at the age of two and a half years.

   This species has a limited appeal as a house plant, and will probably never be common in cultivation - I have never seen it at our local nurseries, it is available occasionally from a number of nurseries, including Mesa Garden, and Out of Africa.

 
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