Sempervivums - Love them or hate them?
A customer of ours once said, Theyre like Marmite you either love them or hate them. She was referring to our ever-expanding collection of sempervivums or houseleeks as they are more commonly known. Personally, I think they have a lot going for them they are evergreen so can provide you with a vast array of colour on those dull winters days, they are drought tolerant and hardy to -15 (one of the most frost-resistant succulents), they multiply and spread with ease and little intervention, and are very easy to propagate. Furthermore, they have such shallow roots that they can be planted in those small nooks and crannies where little else will grow. Apart from occasional root attacks by vine weevils, cutworms or root mealy bugs and occasional aphid infestations, pests are few and they appear to be remarkably resilient and disease resistant.
Sempervivums are alpine succulents of the Crassulaceae family a family which also includes Sedum, Echeveria and Crassula. There are approximately 50 species and over 3000 named cultivars. They were traditionally used on roofs as they were believed to provide protection against lightening and sorcery. Their natural habitat is 3000 8000 ft above sea level in the mountainous regions of central and southern Europe or the Middle East. In such locations they are exposed to a climate of extreme temperatures (hot and cold) and limited moisture. Derived from the Latin semper which means always and vivum which means living, direct translation means always alive. This refers to their ability to tolerate extremes of temperature.
Sempervivums are also referred to as Hen and Chicks - the chicks are the offsets (young plantlets) which are produced on stolons firmly attached to the parent plant, the hen. Be warned, this genus is monocarpic which means that each rosette only flowers once and then dies. However, this is not usually a problem as most species/ cultivars have produced a number of offsets/chicks before the parent plant flowers. The dead rosette can easily be removed and the chicks then continue to thrive and fill the hole left by the dead rosette.
Propagation is either by seed or offsets. Sempervivum flowers are pollinated by insects. Star-shaped fruit containing fertile seeds may be produced. The fruit should be left to dry then can be lightly crushed to expose the seeds. These should be sown in early summer and germination should occur within two months. The new offspring is likely to differ from the mother plant due to hybridization but this can produce appealing results. Several new named cultivars have appeared as a result of deliberate crosses.
Sempervivums spread rapidly by offshoots which can be left to form a mat of rosettes. Alternatively young rosettes can be lifted with roots attached and placed elsewhere in the garden. Smaller offsets can be planted in a small pot of gritty compost until rooted and established. Ideally, offsets should be removed in spring or early summer as sempervivums become dormant over the winter months.
To really appreciate the wonder of sempervivums it is important to consider the texture and shape of the leaves (glossy, matt, velvet or webbed). Sempervivum arachnoideums leaf tips are connected by a cobweb of white hairs and Sempervivum 'Icicle' has a wonderful frosted effect to the tips of the leaves. Consider, also, the extensive range of colours available - lime to green, blue to lilac, orange to brown, red to purple and almost black. Furthermore, look at the leaf formation - the wonderful patterns produced and appealing symmetry. Some species/cultivars have darker tips. Sempervivum calcareum 'Extra' has neatly packed bluish green rosettes with dark reddish purple tips which show off its attractive symmetry to perfection. Its beauty was recognized in 2008 when it was given an Award of Garden Merit (AGM).
To add further interest the appearance of sempervivums varies throughout the year. Rosettes often become rosier as the season progresses. Sempervivum 'Gallivarda' is an attractive two-toned red and green in the summer and then becomes a uniform red in the winter, S. 'Merlin' takes on an attractive orange glow as the season progresses and S. calcareum 'Pink Pearl' takes on a lovely pink rosiness.
Good drainage is vital for these gems to thrive so in our climate, where winters can be very wet, it is advisable to mix some grit or sand into the planting medium and to finish with a top dressing of fine grit around the planted rosettes. This not only improves drainage but helps to set off their colour and form to perfection. Along with good drainage sempervivums need to be planted in a sunny position as the colours of the rosettes are better in brighter light and they will all become a similar shade of green if planted in shade.
Sempervivums are perfect for the rock garden and equally stunning in troughs/containers. Good drainage holes are essential when planting them in containers. They can also be planted in the crevices of walls and look good as an edging to pathways and drives and in the gaps between paving stones. A wide variety of sempervivums planted together in a border or container can look stunning as they grow and merge together. Alternatively, two or three varieties planted as small offshoots in geometrical patterns can be equally eye-catching.
With sharp drainage and a sunny site sempervivums can be virtually left to do their own thing providing you with a riot of colour all year long. A large collection of sempervivums, in excess of seventy varieties, are available at Stonyford Cottage Nursery, Cheshire, along with borders and containers showcasing them to get you inspired. They are available for sale at the Nursery, by mail order and at various Plant Hunters Fairs held throughout the North West. Will it be Sempervivum 'Little Flirt', which lives up to its name, or the intensely shiny red S. 'Tordeurs Memory' that will take your fancy, or the intriguing S. octopodes var. apetalum which sends its offsets out on long stolons the choice is yours. Be warned, though, you might become addicted. Love them or hate them? - the decision is yours.
First published in the Cheshire & Friends Group Newsletter, Autumn 2010
and subsequently in Cornucopia Issue 29.
© Copyright for this article: Angela Overland
This article was taken from a copy of Cornucopia that was published in 2012. You could be reading these articles as they are published to a national audience, by subscribing to Cornucopia.