Tuberous Drosera grow from underground spherical storage stems called tubers similar to white potatoes. (Photo 4-4) Some tubers have scales. Tuber color varies to include shades of white, red, pink, orange, and yellow. Tuber shape varies between species but is reasonably constant within a species. Tuber size in some species can exceed IV2 in. (3.8 cm) in diameter. (Photo 4-5) The growth habit of tuberous Drosera ranges from low growing rosette forms to erect and climbing forms.
Tuber depth is different for each species. If tubers are not planted at the required depth for a particular species, tubers will be formed at progressively lower levels in succeeding years until the appropriate depth is reached. D. gigantea, for example, has the deepest tubers reaching depths of 5 ft. (1.5 m) or more.
The new tubers, in some species, are formed within the cavity formed by the previous tuber which eventually forms a 'skin' around the new tuber. Old tubers have been found with up to 50 layers of 'skin'. It is believed that the skins protect the tuber from high temperatures and prevent desiccation. In some species the skin deteriorates and the tubers are naked. (Fig. 4-5)
Brush fires are required for some species to flower, while in other species fire
Fig. 4-5 Drosera stolonifera plant showing tuber and development of a secondary tuber which can produce a new plant at the start of the next growing season. The plant utilizes the food reserves in its tuber to establish itself. Later in the growing season excess food produced by photosynthesis is stored in the new tuber. The new primary tuber forms within the casing of the previous years tubers. The old casings form protective layers around the newly stored food.
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