Family: Didieraceae
Habitat: Madagascar, in spiny thickets on sandy dunes
Cultivation: Keep it dry in Winter and water regularly in Spriing and Summer, choose a well-draining substrate but with some peat added, put it exposed to filtered light.
Curiosity: It was named after the naturalist Alfre Grandidier, and the plants of its two species are also called “Octopus trees”, for the sometimes twisty form of its branches, that might look like tentacles.

KEY FEATURES

Didierea is a genus of succulent plant in the family Didieraceae. Its name comes from the naturalist who Alfred Grandidier. It has only two species of plant, endemic to Madagascar: Didierea madagascariensis and Didierea trollii, that are dwellers of the typical ecosystem of the spiny thicket/wood. They are rare species and are listed in the appendix II of the CITES convention. CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) is an international agreement between governments that has the aim to ensure that international trade in specimens of wild animals and plants does not threaten the survival of the species. The Appendix II, in particular, lists “all species which, although not necessarily now threatened with extinction, may become so unless trade in specimens of such species is subject to strict regulation.

Both the Didierea species are shrubs and trees with spiny, succulent leaves, deciduos in the arid season, and stems capable of store water. The genus originally included 7 described species, of which only 2 are nowadays accepted. Didiereas are dioecious: this means that there are “male” and “female” plants. Male plants produce only male flowers, while female ones produce only female flowers, unlike in many other genera, in which flowers are hermaphrodites.

The habitat of these trees are sandy dunes, in spiny thickets, with an annual rainfall between 330 and 570 millimeters and more than eight months that stay completely arid and rainless during the year.

Didierea can reach an height of 4-6 meters. They can be considered shrubs or trees and are also called “Octopus plants” for the sometimes twisty form of its branches, that can be rather prostrate in D. trollii, resembling even more some kinds of tentacles. Leaves and spines are very peculiar, growing in clusters directly on the main trunk. In Didierea madagascariensis the clusters are of 4 elements (groups of 4 spines along with groups of 4 leaves), while in D. trollii they are groups of 3. Also, while in Didierea madagascariensis leaves are lanceolated and narrow, in D. trollii they are instead ovate-elliptical, and the spines in the latter species are much shorter.

Flowers grow, always in clusters, at the top of the branches, and the blossoming can occupy several meters of the branches. They are white in D. madagascariensis and greenish white in D. trollii, with pink stamens in the centre (of only the male flowers, as the female one don’t have stamens). We remind that stamens are the male part of any flower, in which the pollen is formed.

VARIETY AND TYPES

Here below are the two species of Didierea:

• Didierea madagascariensis
• Didierea trollii

TIPS FOR GROWING

Didiereas are very tough and resistant. Here below are our tips of cultivation:

• Place it in a bright spot, but with filtered light available: too much direct sunlight might be harmful. These plants are in fact native to a thicket and grow in the shade of other trees.
• Didiereas are not very resistant to cold temperatures: we advise to keep them indoors during the winter, at temperatures around 10-12ºC. Never leave them at temperatures below 5ºC.
• Choose a well-draining soil, but richer in nutrient elements: Didiereas might enjoy some peat, unlike other succulents.
• Water regularly during the growth season, around once a week, always waiting for the soil to dry up completely before each irrigation. In Winter, suspend any irrigation.
• Fertilize once a year with a product specific for succulents, diluting it to half the doses recommended on the label.
• Repot anytime you see that the plant outgrows its pot. It may tall but it’s not the fastest grower among all succulent plants.

The propagation is usually carried out either through seeds or by grafting it on the more tough species Alluaudia procera, that is also partially related to Didieras.