Advice on how to care for sempervivum plants
Sempervivums are tough, translating from Latin as "always alive". The wild species are mainly found on mountains in Europe, such as the Alps, where they survive dry summers and cold winters covered by snow.
If there is a weakness, sempervivums don't like being waterlogged. This is easily prevented by planting them in a well-drained, soil-based compost. We suggest John Innes No 3 - available from any garden centre or DIY store. Mix this with horticultural grit (again, widely available as above) at a ratio of 3 parts John Innes to 1 part grit. A generous top dressing of grit will also help combat excessive moisture, as well as providing an attractive finish. All containers must have drainage holes in the base.
Sempervivums are versatile plants. They can be kept in pots, bowls, troughs, or in open ground such as a rock garden. They're outdoor plants, part of the group of alpines or rock plants, which like a sunny position - ideally getting as much sun as possible, but at least for part of the day. They survive sub-zero temperatures in winter and natural rainfall is enough in spring/summer, so supplementary watering is not usually required once they're established.
Sempervivums need plant food, but make sure you don't overfeed. Initially, there'll be enough in the soil. Afterwards, a modest liquid feed (preferably with an NPK ratio of 7:7:7 or similar) once a year in April or early May will keep your plants growing well and looking their best. Sempervivums can vary considerably when grown under different conditions - in addition to any change of appearance throughout the year. Generally, don't spoil them as they're tough alpine plants.
Mature sempervivums might flower in the summer months. The flowering rosette will afterwards die, survived and replaced by the surrounding offsets. Attractive clumps quickly form. The flowers are greatly admired - and appreciated by bees and other pollinators. It's a good idea to remove dead flower stalks to maintain best appearance. Old clumps can be easily replaced, if and as necessary every few years, by detaching offsets and replanting.
Growing sempervivums in pots is fine. Giving them even more space in a bowl or trough is better. These look great as a feature on the patio, by the front or back door, along a garden path or driveway, or at the entrance to a greenhouse. Mixing and matching different varieties will enhance each plant's individual beauty. And their on-going appeal and interest is stimulated by seasonal changes in colour - always providing a focal point in the garden. Some enthusiasts have collections of up to a few thousand different varieties.
Here's a short film on how to plant sempervivums in a trough, including the best soil mix to use: