Types of Sempervivum: the most beautiful at a glance

Did you know that there are over 7000 varieties of houseleek? There are differences, for example, in rosette size, leaf colour and the “hairiness” of the beautiful rock garden plants.

Houseleeks (Sempervivum) are survivors that are easy to care for. They grow in places where many other plants would die of starvation and look decorative at the same time. These are just a few reasons to get yourself a houseleek. However, if you are having a hard time deciding which of the many houseleek varieties to choose, this article is just what you need. We present the most important Sempervivum species for the garden and give examples of cultivars – from red houseleeks to cobweb houseleeks and some houseleek rarities.

Types of Sempervivum: how many are there?

Houseleeks form a genus within the family Crassulaceae. Opinions are divided on the number of species, ranging from about 30 to 200, and the number of varieties of houseleek is now thought to be over 7000. This is because there are some amateur growers who specialise in growing Sempervivum rarities. So it’s hard to keep track of them all. Basically, however, it can be said that all houseleek species are classified as hardy, forming leaf rosettes and flowering on elongated shoots before the individual rosette dies.

Tip: When buying, do not rely too heavily on the described leaf colour of the Sempervivum variety. This is often heavily dependent on conditions such as the season or the location, and can be significantly different in your garden than in pictures or in the garden centre.

The most beautiful houseleek species and varieties at a glance

In the following sections we present some Sempervium species and cultivars relevant for home gardens, as well as houseleek rarities. Many species are species hybrids. This means they are the result of crossing two different species, which can happen by breeding, but also naturally. Fertile species hybrids can then in turn give rise to new species. The boundaries are therefore fluid and due to the enormous diversity of houseleek species it is difficult to distinguish between hybrids, new species and cultivars.

Thunderplant, common houseleek or true houseleek (Sempervivum tectorum)

The common houseleek is one of the most vigorous houseleek species. It prefers neutral to slightly acidic soils and thanks a little nutrient richness with larger rosettes and a greater number of offshoots. As a result, the rosette size can range from 4 cm on poor soils to 15 cm on more nutrient-rich soils. After a few years, the houseleek flowers in July and August. The shoot then stretches up to 30 cm in height and purple-pink star-shaped flowers appear at its tip. Thunderplant is also the Sempervivum species that has been best studied scientifically, so information on healing effects and possible uses usually refers to it.

There are innumerable varieties and hybrids of the true houseleek. Most often available in stores are:

• ‘Atroviolaceum’: This old variety was first mentioned as early as 1929. Its distinctive feature are large rosettes and leaves that turn from green to red-purple.
• ‘Metallicum Giganteum’: ‘Metallicum Giganteum’ is a variety that forms very large rosettes. Leaf colouration ranges from green to metallic red-brown.
• ‘Othello’: ‘Othello’ is a red houseleek – even if the leaves are usually not deep red all year round, but green at times.

Tip: The true houseleek is particularly good at converting the nutrients from a fertiliser into more magnificent yet healthy rosettes. For example, you can apply our Plantura Tomato Food around the rosettes once a year in spring. In line with the requirements of Sempervivum, our fertiliser has more potassium in relation to nitrogen. It is also a primarily organic slow-release fertilizer that is completely animal-free and safe for pets.

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Wulfen’s houseleek (Sempervivum wulfenii)

Unlike many other species, the flowers of Wulfen’s houseleek are mostly yellow. It also has rather green foliage, whose leaf tips only turn slightly reddish in autumn. Otherwise, Wulfen’s houseleek is quite similar to the true houseleek and is suitable for neutral to slightly acidic soils. Sempervivum wulfenii does form runners, but is much less eager to spread than Sempervivum tectorum and therefore easier to keep in check.

Cobweb houseleek (Sempervivum arachnoideum)

The name already indicates the special nature of this species, because the rosettes of Sempervivum arachnoideum look as if they are covered with many spider webs. However, this is not because the plants are attractive to spiders. Instead, the connection to spider webs comes from innumerable hairs, so-called trichomes, on the leaves that connect. The leaf rosettes of cobweb houseleeks remain rather small with a diameter of 1 cm to 4 cm. Over time, they form compact cushions 2 to 5 cm high through offshoots. After a few years of growth, the individual rosettes begin to stretch and flower. Pink star-shaped flowers then appear on 10 to 15 cm high shoots from July to August. Cobweb houseleeks are considered acidophiles, so do well with rather acidic substrates.

Suitable varieties include:

• Ssp. Tomentosum: This subspecies has a compact habit with somewhat flatter rosettes and is characterised by a pronounced formation of “spider webs”.
• ‘Kramer’s Spinrad’: ‘Kramer’s Spinrad’ has a vigorous growth and rather fanned out rosettes that only show spider webs in the centre. The leaves of this variety turn deep red in summer.
• ‘Silberkarneol ‘: The variety ‘Silberkarneol’ has green leaves that turn a beautiful pink-red in spring. Hairs are only found on the tips of the leaves and usually they do not join together to form webs.

Teneriffe houseleek (Sempervivum ciliosum)

The leaf edges of the Teneriffe houseleek are also very hairy. Unlike the cobweb houseleek, however, they do not join together to form webs. Another difference to Sempervivum arachnoideum is the somewhat greater spreading ability, which Teneriffe houseleeks owe to the formation of longer stolons and greater vigour. The rosettes of Sempervivum ciliosum reach about 5 cm in diameter and the flowers on the 10 to 15 cm high shoots are yellow-green or reddish-brown in colour.

• ‘Borisii’: The leaves of this cultivar are grey-green – but so heavily hairy that they have a silvery sheen. The rosettes of ‘Borisii’ are characterised by a medium-sized and very compact spherical growth.

Tip: The hairs of cobweb Teneriffe houseleeks hold moisture around the leaves longer. This can be their undoing, especially in winter when it is damp for a long time, and individual leaves can start to rot. To prevent this, these species should be planted in definitively dry places and should also get enough sun in winter to dry out completely. For more tips on planting and caring for Sempervivum, see a separate article.

Calcareous houseleek (Sempervivum calcareum)

As the name suggests, the calcareous houseleek is a lime-loving Sempervivum species. It forms rosettes 4 to 8 cm in diameter and flowers whitish on shoots up to 25 cm high. The leaves are mostly blue-green and have intensely red tips.

Rolling hen-and-chicks (Sempervivum globiferum)

This species is a representative of a different section than the other houseleek species presented here. This is noticeable when flowering, because in Sempervivum globiferum the flowers are tubular to bell-shaped and usually yellowish in colour. There are different subspecies that have adapted to different site conditions from acidic to calcareous.

The main varieties available include ‘Mrs. Giuseppi’ and ‘Tederheid’ available. Externally they barely differ, but ‘Tederheid’ is described as more robust and more tolerant of moisture.

Other species and Sempervivum hybrids

The list of Sempervivum species and varieties could go on for many pages. Two varieties with large rosettes include Sempervivum macedonicum with red-green leaves or Sempervivum marmoreum, forming rather loose cushions with rosettes up to 8 cm in diameter. In the meantime, there are also a large number of Sempervivum hybrids, i.e. crosses of two or more different species. Examples include:

• ‘Cono’: The hybrid ‘Cono’ forms rosettes about 3 cm tall. The leaves are green, but develop blood-red tips depending on the season. The fine hairs that only appear on the tips of the leaves are also funny to look at.
• ‘Bronze-Pastel’: ‘Bronze-Pastel’ is a hybrid that has been tried and tested for a long time. Over the course of the year, you can see the constantly changing leaf colour, which ranges from almost golden to green to deep red.
• ‘Red Papaver’: ‘Red Papaver’ is a coral-red houseleek, but not all year round. At times the leaves of this variety, which are slightly hairy at the edges, change colour to green.