The roof root, Sempervivum tectorum, is a very old cultivated plant that appears in the plant and herb books that were written towards the end of the Middle Ages. Its natural range begins in southern Germany and extends in a wide belt down to Asia Minor, where the roe root originally inhabited mountains, all of Europe apart from the north and east. In the following you will learn a lot about the interesting plants, care and wintering of the thunderwort.

Roof root, thunder root – plants and locations

Thunderbirds were found in the highest regions of the Pyrenees, on the French Massif Central, in the Alps to the southeastern edge and in the southern Apennines.

From all over there people have been collecting the pretty plant for a long time, it grew willingly in flatter regions and overgrown there, today there are wild thunderbirds everywhere, at every altitude, from Scandinavia to Ireland, all over the rest of Europe, across the Caucasus to to Iran.

However, this spread into the lowlands only happened because many people found the rosette plants highly attractive and decorated their homes with it, which is why the roof root is often called houseleek or houseleek in German-speaking countries (along with around two dozen other flattering or funny ones Names, see below).

The “real roof houseleek” or “common houseleek” is the best known and most widespread houseleek (more on many other houseleek below), it grows perennial and evergreen with rosette-shaped leaves that reach between five and twenty centimeters in diameter per rosette and only a few centimeters high.

The roof root can be planted anywhere that a little plant decoration is needed, provided the location is light enough and offers clear differences in the seasons. Thunderbirds can therefore be planted in many places in the garden, even on the balcony or terrace, in the appropriate environment.

It is not for nothing that the rooftops have chosen the roof as their preferred settlement location, they are real fresh air fanatics who are very difficult to keep in the room all year round. If you wanted to give it a try, you would have to open the window very often in summer, in winter the roof roots will only survive in a cool place where the temperatures do not rise above 10 degrees.

In addition, roof roots need a lot of light, in the garden, balcony and terrace a sunny location – in the room too, but there the location behind a window pane that reduces the light intensity could already be too dark, which is then noticeable by the fading of the leaf colors.

On the other hand, it is really worthwhile to choose the sunniest corners outdoors, the more sun a roof root gets, the more splendid the leaf colors will develop. Four hours of sun are the minimum in our latitudes, so that the rosette color is reasonably attractive, less means a lack of light and pale plants that can get out of shape.

Caring for the roof root

The roof root from the mountains is used not only to the sun, but also to a rather nutrient-poor soil on which any precipitation drains off quickly. Such an environment is also good for the roof root in the garden, so the environment in the rock garden, in a dry bed or on a wall, in the crevice with little soil, will definitely appeal to it.

If the roof root is to be planted in a bed with a substrate that actually contains good humus, you should loosen the soil beforehand and mix in some bird sand, gravel or pumice stone, this would also be the right soil for a culture in pots or pots (or in any other imaginative Vessels, which can be quite flat), earth, sand and gravel in equal parts.

Such a soil also fulfills the humble plant’s second minimum requirement: it never wants to get its feet wet, in the mountains, water always flows away quickly, which is why every vessel planted with thunderwort needs a drainage hole.

Otherwise, the roof root is really frugal and a real survivor who is not to be seriously shocked by a cold, wet winter or a tropical hot summer.

You do not need to fertilize a thunderwort, too many nutrients would rather irritate the plant, it could lose its beautiful color or start to rot.

If individual rosettes in the eyrie weaken, this is not an alarm signal, but completely normal, after the flowering, the withered rosettes die.

Hibernate roofwort, thunderbird

The roof root overwinters exactly where it is growing and it will have no problems with frosty temperatures – those who grow high in the Alps can really get off the cold.

Rather, the reverse case could lead to the premature death of a thunderwort: If you cultivate the roofwort in your room and expect it to be at temperatures at which you feel comfortable. Put them outside, a roof root does not want more than 10 degrees in winter, and it’s too dark in their room too.

Thick-leaf plants that are suitable for indoor keeping, which are very similar in appearance to a roofroot, are certain varieties of echeveria (e.g. Echeveria agavoides) and graptopetalum (e.g. Graptopetalum bellum), you should rather allow thunderbirds their freedom.

The multiplication of the thunderwort

Make many out of one, no problem at all for a houseleek, because it constantly develops new daughter rosettes. You can carefully separate these in the spring and place them separately in soil or in a pot.

You could also grow root roots from seeds, an option often practiced by lovers of growing rare varieties, but if you have a choice, avoid fiddling with the microscopic and fine seeds. If it has to: The dust-fine Sempervivum seed must not be covered with soil, but it must be pressed lightly onto the potting soil, the best way to do this is with a completely dry and smooth piece of parchment paper. The surface of the soil in the nursery pots must never dry out, but you can only spray water on, the seedlings would not withstand a “waterfall” from the watering can.

If the environment allows it, the thunderbird will also spread automatically, through runners, at the tips of which new rosettes form, and through seeds, with the help of the wind.

Diseases and pests

You do not need to worry about diseases and pests with roof lice, all house lice are extremely robust and are neither sick nor damaged by pests so much that action is required.

If your thunderbird does show signs of pests or diseases, something is fundamentally wrong with the husbandry and nutrition. Then that has to be changed, otherwise the roof root would fall ill again and again.

Roof root – many names, many shapes, many types

The houseleek is botanically called Sempervivum, from “semper” means “always” and “vivus” means “living”, and its popularity shows that not only plant beginners appreciate “ever-living” plants. The “root” stands for “root”, “plant”, the “tectorum” for the most famous species of roof root, this roof root has made itself so popular as a medicinal and ornamental plant that it has been given numerous nicknames in many European languages Most of the German-speaking areas: Jupiter’s beard and roof herb, roof leek and roofwort, roof bulb and Donarsbart, Donnerbart and Donnerkopf, Donnerkraut and Donnerwurz, Dunnerknöpf and Gewitterkraut, Gottesbart and Grindkopf, house sorrel and houseleek, houseleek and wallwort, earwort and stone rose, wart herb and ciderwort – all names for exactly the same little plant.

As the most common houseleek, Sempervivum tectorum is also the favorite of houseleek growers; around 7000 varieties have now been bred by it (and its close relatives), among which gardeners can choose, with decorative flowers that are always slightly different in color or with slightly different, extremely interesting rosette shapes . Breeding is based on two natural forms:

  • Sempervivum tectorum var. Tectorum with leaves that are hairy at most on the edge and smooth leaf surfaces that can occasionally have short hairs.
  • Sempervivum tectorum var. Arvernense with downy hairs that extend over the entire leaf.

However, the roofwort is by no means the only houseleek species, there is rather a considerable number of houseleek, between 40 and 200 species have been described by different authors. Between 40 and 200 because the genus Sempervivum is one of the youngest genus in the thick-leaf family, which is believed to be not yet in a stable phase of its evolution, the house lice “mutate happily and vigorously “.

In addition, all members of the genus are closely related, and they can form natural hybrids, which then often back-cross and cross again – in fact, this results in a fairly infinite number of species or varieties, which can often no longer be properly delimited are.

The exact botanical classification of the Sempervivum is important to the roof root and houseleek lover whenever he wants to start breeding. Then he might first choose from around 75 natural forms from Sempervivum alidae to S. zeleborii. He can and must then choose again within the species; B. among around 120 different-looking natural forms, perhaps a slightly ornamental roof root with reddish leaves from the Spanish Sant Maurici Lake, or an almost geometrically neat growing, light green S. tectorum from Ajdovski Gradec, a hill known for its archaeological finds in Slovenia.

If he prefers to stimulate his visual imagination, he takes a catalog with cultivars and looks at around 350 pages with 20 pictures each of Semperviva (Semperviva), all of which have tones between green and gray, purple and wine-red, brown and pink and all the rosette shapes a creative artist could think of.

Like S. tectorum, most of these houseleeks prefer dry, warm and stony locations, but among the many species there are also houseleek that tolerate humus soils and even those that you can settle in moist soil.

The roof root has a lot of fans

Because the Semperviva can really fascinate with its unbridled diversity, there is a large community of “Semps” friends who breed and collect and take photos and trade.

The best-known Semps community is the “Sempervivum / Jovibarba” specialist group from the “Society of Perennial Friends”, which can be reached via

At the moment, this lovers’ association seems to be the only one in the open, although towards the end of the last century, roof root and houseleek lovers also met in Belgium (Sempervivum Werksgroep), in Great Britain (Sempervivum Society) and in the USA (Sempervivum Fanciers Association) organized, but these associations have all ceased to exist, so the post of worldwide “Sempervivum Grand Master” would be vacant.


The roof root is really a “plant for all occasions” which, in addition to absolute frugality, also shows an almost breathtaking wealth of variants. A favorite plant for “lazy gardeners”, a challenge for creative gardeners, a life’s work for collectors – gardeners with thunderwort will definitely not get bored.

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