The super-tough ‘houseplants’ that just love it outside
TENDER succulents have never been more popular, but these fascinating houseplants offer little to those looking to enhance their outdoor space. As luck would have it, there is a tribe that possesses the striking good looks of their lily-livered kin but are so blinking tough that they will light up the garden in the depths of winter.
Step forward sempervivums, a large family of low-growing succulents that originate predominantly from mountainous areas of Europe, such as the Balkans and Caucasus. Commonly known as houseleeks, they can endure wind, rain and snow and will easily survive temperatures down to -15C or lower.
These alpine plants form a rosette of leaves and come in a dazzling array of colours, including bright yellow, green, grey, blue, red, pink, purple, brown and near black. Some are a solid shade, while others are embellished with darker or lighter leaf tips, or have leaves that are flushed with another hue.
Many have an amazing party trick… their rosettes are able to change colour at different times of year. Take for example, Sempervivum ‘Fuego’. This German-bred variety has burgundy-red rosettes from autumn until spring, turning green in summer, with only the outer tips showing any reddish tints.
Long before they were grown as ornamental plants in this country, houseleeks were regarded as a universal remedy by herbalists. A drink made from its juice was prescribed for ringworm and applied externally to shingles, warts and rashes. It was used for eye and ear complaints, and to treat insect bites and stings.
Over in mainland Europe they were believed to protect against thunder, lightning and fires, and were deliberately grown on roofs to guard the occupants. In the 9th Century, Charlemagne, the first Holy Roman Emperor, even ordered that houseleeks be planted on every building within his lands and holdings.
The first sempervivum varieties to be developed from wild species appeared in the late 1800s, but breeding only really took off in the later half of the 20th Century. Today, there are more than 1,500 different ones available to gardeners on our shores, created by breeders in Britain, the USA and across Europe. Individual rosettes vary greatly in size, ranging from ½in up to 12in across.
Plants produce baby rosettes on runners, allowing them to spread and form dense mats of foliage. Once rooted, the offsets are easily tugged up from the ground, allowing them to be positioned elsewhere around the garden. Apart from their showy rosettes, sempervivums form stout wands that are topped with starry pink, red, purple or cream-coloured flowers in summer.
The 4in to 12in-long stems emerge from the centre of rosettes that are two to three years old. Sadly, the individual rosette dies once flowering is over.
Sempervivums are fantastic in rock gardens, cracks in walls, gravel gardens and all sorts of containers, such as ceramic sinks, troughs and bowls. I once displayed 24 different varieties in small pots arranged in a shallow window box. All plants need is a sunny spot and very well drained soil or compost.
A novel way of showing them off is to make a brick planter. Take a reclaimed engineering brick and fill each channel with compost. Make a small hole in the top of each hole before dividing up a clump of sempervivums. Set a rosette into each channel, making sure it has a length of stem attached bearing plenty of roots.
These succulents require virtually no maintenance. Water very occasionally in summer and hoick out dead rosettes after flowering – fill the gap with a little gritty compost to help offsets take hold. Birds will sometimes pull up rosettes, so check clumps regularly and firm back in place if necessary.
They change colour several times a year. What a party piece!