Sempervivum arachnoideum

Sempervivum arachnoideum, also known as the cobweb houseleek, is an alpine species that owes its name to the fine veil of white bristles stretched around small rosettes that seem to be trapped in a spider's web. These fine sparkling bristles, woven on the triangular leaves, further accentuate their geometric appearance. On a beautiful summer day, like an unexpected gift, small star-shaped flowers, ranging from pink to crimson, with fleshy petals, emerge from the heart of the oldest rosettes. This houseleek is a small succulent plant ideal for arid and mineral areas, covering them with its beautiful woolly carpet. It requires nothing more than an open location. Without any maintenance, it miraculously survives with almost no soil, in a dry, poor, siliceous or limestone environment, and relies solely on rainwater, even if it is scarce.

From the Crassulaceae family, this cobweb houseleek proves that poor soil and a mineral landscape can also accommodate beautiful specimens with vibrant colours. This sempervivum is quite variable in appearance. It lives on rocks or in scree, dispersing its fine seeds in crevices and clinging to the smallest fissures to slowly form small colonies of rosettes of different sizes, juxtaposed, not exceeding 8cm (3in) in height. With time, it can spread out on the ground through its stoloniferous stems, forming a carpet that can reach up to 60cm (24in), perfectly adapting to the terrain. Resembling small artichokes measuring 1.5 to 3cm (1in) in diameter, each rosette is composed of numerous pointed leaves, without petioles, connected to each other by a silky weaving. The white threads, stretched between the leaves, shimmer in the sunlight. The roots of this perennial are thick and long. They penetrate deeply into rock crevices, ensuring good attachment to the walls while drawing water from deep sources. 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 floral stems develop in summer, formed by thick stems that bear 1 to 5 flowers with 8 to 10 pink petals and a purple median.

Sempervivum arachnoideum is a boon for gardens where the soil lacks thickness. It thrives where few species survive, colonising abandoned spaces. You can still enjoy this hardy perennial if your soil is poor, rather dry, stony, rocky, or even slightly chalky. It withstands temperatures below -15°C (5°F), requires no maintenance, and promises to animate any pile of stones, a wall, or even a green roof. Houseleeks are easy-to-care-for succulent plants, offering flowers and foliage in various shades that create stunning compositions. Magnificent in pots, especially in low terrine-type pottery, they are irreplaceable in borders, troughs, or rockeries, alongside London Pride (Saxifraga umbrosa), wall bellflowers, or Lewisia cotyledon. These miniature perennials quickly inspire the desire to multiply them. Consider choosing companions with staggered flowering and colourful foliage for a varied and joyful rockery.