Sempervivum x arachnoideum Alpha

Sempervivum 'Alpha' is a classic. Created in 1927, it is one of the first hybrid varieties of houseleek. Its tight rosettes appear green in spring, then gradually turn red, becoming a beautiful coppery brown in autumn. Its silky leaves are delicately connected by silken threads, as if woven by a spider. In summer, a small cluster of star-shaped flowers in bright carmine pink emerges from the heart of the oldest rosettes. This houseleek is a small succulent plant ideal for arid and mineral areas. It requires nothing more than an open location. Without any maintenance, it miraculously survives with almost no soil, in a dry, poor, siliceous environment, relying only on rainwater, even if it is scarce.

Sempervivum belongs to the Crassulaceae family. It grows on rocks or scree, scattering its fine seeds in crevices and clinging to the smallest cracks to slowly form small colonies of rosettes of different sizes. The hybrid cultivar 'Alpha' was created in 1927 by the German nurseryman Georg Arends, from Sempervivum tectorum (houseleek) and S. arachnoideum (cobweb houseleek). S. 'Alpha' has in turn become the ancestor of many cultivated houseleeks today. It remains a very popular variety, and one of G. Arends' greatest successes.

The tightly-packed rosettes of Sempervivum 'Alpha' do not exceed 10cm (4in) in all directions when mature. Over time, it grows through its stoloniferous stems to form a spreading cushion reaching 50 to 60cm (20 to 24in) on the ground, perfectly conforming to the terrain. Resembling a slightly open artichoke, each perfectly organised rosette is composed of numerous fleshy, pointed leaves without petioles. The white threads, stretched between the central leaves, shimmer in the sun, as do the cilia that border them. The reddish colour of the leaves intensifies in summer. The flowering appears on rosettes that are 2 or 3 years old, which will then disappear, having ensured the plant's perpetuity by producing several small rosettes on the periphery. The flower stalks develop in summer, formed by thick stems that bear 1 to 5 flowers with 8 to 10 bright carmine petals. The roots of this perennial are thick and long; they penetrate deeply into the crevices of rocks, ensuring a good grip on the walls while drawing water from deep below.

Sempervivum 'Alpha' is a boon for gardens with thin soil, where few species survive, colonising abandoned spaces. You can still enjoy this hardy perennial if your soil is poor, rather dry, rocky, stony, or even slightly calcareous. It withstands temperatures below -15°C (5°F)) and requires no maintenance. It promises to enliven any pile of stones, a wall, or even a green roof. Houseleeks are extremely easy-to-care-for succulent plants, offering flowers and foliage in various shades that create stunning compositions. They are magnificent in pots, especially in low, 'bonsai-style' terracotta containers, and they are irreplaceable in borders, troughs, or rock gardens, alongside sedum, saxifrages, wall bellflowers, or Lewisia cotyledon. These miniature perennials quickly inspire the desire to multiply them. Consider choosing companions with staggered flowering times (thyme, Saponaria ocymioides) and colourful foliage (Sedum spathulifolium) for a variegated and joyful rock garden.