The sempervivum are succulent, evergreen plants, widespread in most of the Mediterranean basin; they belong to the crassulacee, and the genus sempervivum has a few tens of species; it is not always easy to distinguish the species of sempervivum because these plants vary greatly their physical appearance based on the characteristics of the place in which they live. In addition to this they hybridize with great ease, even in nature, so there are dozens of different varieties, which often have minimal differences from one another.
THE sempervivum they produce thick rosettes of fleshy, triangular, pointed leaves, often with a single spine at the apex of each leaf; the leaves are varied in color, from light green to purple red; the dimensions of the rosettes range from two to twenty centimeters, depending on the species, and depending on where they live.
Every single rosette tends to produce small side rosettes, so colonies of rosettes are commonly found sempervivum trimmed, which can also cover a very large area. Every 3-4 years the older rosettes develop a short fleshy stem, covered with small leaves, at the apex of which bloom with star-shaped inflorescences, white, pink, yellow or purple; at the end of the flowering in general the rosette that produced it dries up, but this event is hardly noticeable, since quickly new small rosettes take the place of the deceased one.
Cultivating the sempervivum
The name of these plants tells us what their rusticity is: although they are succulent plants, sempervivums develop in prohibitive conditions for other plants, both for lack of water and for winter cold. In fact, many species of sempervivum originate from the Alpine mountains, where they grow among the rocks.
These plants need a very sunny position, if placed in partial shade they can develop, but do not like the complete shadow.
They prefer very well drained soils, and completely free of water stagnation; in fact they are plants particularly suitable for rock gardens, as they are able to develop even with minimal amounts of substrate, among the stones.
Once planted the sempervivum do not require special care, and tend to naturalize in the garden, taking up all the space they have available over the years.
Generally they do not need watering, and even house-dwelling animals tend to settle for water provided by watering. Eventually, in case of drought that lasts for a long time, it may happen that the superficial leaves become slightly wrinkled: a single watering can make all the leaves completely turgid again.
They certainly do not like to be watered often, even if they can withstand possible water stagnation, provided they are not the usual cultivation condition.
They are not afraid of cold and frost, and can be grown outdoors throughout the year.
Indicative of their rusticity to the sempervivum tectorum, the name derives from the fact that these plants develop in the little substrate that is created at the intersection of the roof tiles; these plants can also produce large colonies on the roofs of houses, living undisturbed, without the need for any care.
Clear that if placed in a vase, in a good rich soil, sporadically watered, the rosettes tend to become more fleshy and luxuriant, and to produce more showy flowers. We avoid, however, to exceed, because watering and regular fertilizations in the long run lead plants to develop excessively and to become prey to pests and diseases.
I Sempervivum: Similar species
There are succulent plants very similar to the sempervivum, which however do not necessarily share the resistance to frost, and therefore may not always be grown in the garden throughout the year.
- Echeveria: crassulacea native to Mesico, there are rustic echeverias, although many are delicate, and are grown as houseplants; unlike sempervivum, many species of echeveria produce a single large single rosette, often bluish-green.
- Aeonium: succulent plants originating from Africa; have less fleshy foliage than sempervivum, spatula-shaped, elongated; the rosettes develop at the apex of short, thick, often branched stems.
- Monanthes: very similar to sempervivum, but originating from warmer places, they generally do not tolerate frost.
- Jovibarba: one of the genera of crassulacee more similar to sempervivum, often it is not easy to distinguish between the two genera, and many species are attributed according to the authors to one or the other gender.
- Greenovia: very similar to echeverias, with loose rosettes, usually bluish in color, due to the bloom covering the leaves; they are widespread in Africa and the Canary Islands.