About the genus
Kalanchoe, which includes small trees, shrubs, monocarpic plants,and climbers, is included in the subfamily Kalanchooideae of the Crassulaceae. Three subgenera are recognised in Kalanchoe: 1) K. subg. Kalanchoe, a variable group with a wide geographical distribution range; 2) the exclusively Madagascan K. subg. Bryophyllum of which the representatives have pendent flowers; and 3) K. subg. Kitchingia, a Madagascan group of only four species, all of which are rather flimsy plants. These three subgenera were at one time all treated as separate genera, a view no longer upheld.
Geographically, kalanchoes occur in Madagascar, Africa, Arabia, and Asia, with areas of high present-day species diversity recorded for Madagascar, and southern, southcentral, and eastern Africa.
Some species, such as K. beharensis, are tomentose (finely or coarsely hairy) throughout, while others have strikingly purple-mottled leaves, for example K. marmorata. In some species, such as K. thyrsiflora, the inflorescences are densely flowered and club shaped,while in others, such as K. sexangularis, the inflorescences are more diffuse but apically carry numerous, small, tubular flowers with recurved corolla lobes.
How to grow them
In general, kalanchoes are undemanding, largely pest-free, and easy to cultivate in containers.Plants will grow well in almost any soil type, although a well-drained mixture with a high humus content work well for most species. They grow actively during the warm summer months, and produce their often substantial, multi-flowered inflorescences in winter – they are referred to as short-day plants.
Kalanchoes can tolerate very low levels of rainfall in their natural habitats, but in cultivation do better if the soil, especially for container grown plants, is kept moist, but not wet. They cannot tolerate sub zero temperatures and in most temperate regions must be kept indoors or under glass.
Plants flourish in full sun, and under such conditions the leaves of some species, for example K. luciae, will often become spectacularly red or purple.
Kalanchoes can also be grown in semi-shade. Some Madagascan species, such as Kalanchoe manginii, have been used in the breeding of beautiful cultivars, such as K. ‘Tessa’, which can tolerate surprisingly low light conditions.These are perfectly adapted to hanging basket cultivation and do well indoors.
They are easy to propagate from stem cuttings. These can be removed with a sharp knife, and left to dry for a week after which they can be planted directly in the spot where plants are intended to grow in open beds or pots.
Many Kalanchoe species are self fertile and produce copious amounts of dust-like seed that germinates easily. Scatter seed on top of the soil in a seed tray, and lightly cover with some fine, sifted sand. Water the tray from below. Seedlings will start to appear within a week or two. Some species produce plantlets on the margins of their leaves. These will strike root where they fall, or simply place a severed leaf that has plantlets flat on top of the soil.
Text and photos: Gideon F Smith
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