The 'Elephant's Foot' (Dioscorea or Testudinaria elephanlipes) is so oddly fascinating that I am tempted to use that overworn cliche "a must for every collection". Certainly, if only one caudiciform plant is to be allowed into a collection, this is it. The large, winged seed germinates to produce a 1cm (%in) spherical caudex the first year, with a single heart-shaped green leaf. Slender annual climbing shoots follow, like the black bryony, Tamus. its next-of-kin. As the sphere enlarges it develops corky polygonal warts (21.8)and in nature can reach a great age and size—over I m (39in) across. Plants are dioecious and there are three other only slightly less marvellous species with the caudex more or less above ground. All the remaining species, of which there are about 600. have the storage organ below soil level and include the edible yams. It should be noted thai the overground habit, as described above, hasevolved independently in South Africa (D. elephanlipes. D. glauca and D. sylval-ica) and in Mexico ID. macrostacliyal
The 'Elephant's Foot' is much less difficult to keep than was once thought, and there is no need to rob the habitat by importing plants when, under optimum conditions, superb football-sized show specimens can be reared from seed in 10-15 years. The aerial branches delight in full sun, but the caudex is best in shade beneath the staging, and takes continual watering during the summer or while carrying leaves; even in the rest period it should not be baked too dry. Right (21.10): The rare Othonna herrei. whose stems are covered in knob-like woody tubercles tormed trom leal bases, is superficially like Cotyledon wallichiana In cultivation. Othonnas are dormant during summer and need water
Above: (21.11): A seedling Pachycormus discolor from the habitat seen on 21 I The caudex grows lully above ground Small plants are much in demand by lovers ol bonsai. This plant is about 20cm (8in) high.
Right(21 12): Othonna euphorbioides. the most cactus-like ol all succulent Composilae. bears branched spines derived Irom woody inflorescences. This plant, in a 10cm (4in) pot. has grown much taller than in nature
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