The Atlas mountains ramble across northern Africa, rising up from the southern Mediterranean coast. They span from Morocco east to Tunisia, rising as high as the Alps above deserts to create a remarkably cold and dry habitat for plants. Most gardeners haven’t heard of these ranges, though they are mentioned on the news more than ever as war spreads through the Middle East.
This is the homeland of many sempervivums, an incredibly cold hardy genus of succulents that takes snow and drought in stride. Most succulents are from balmy southern Africa, where frost is rare and the majority of them are too tender for frost-tinged gardens. But if you vicariously climb the Atlas Mountains by exploring these widely available plants, even cold climate gardeners will come to appreciate their tough beauty and versatility.
With forty genera bred into 4,000 named varieties, this is an enormous group that is a mainstay of colder northern European gardens, where much of the early breeding began. They’ve been long grown in Europe and Britain, where they were dubbed “house leeks” because as succulents they grow well in roof thatch. Originally it was thought succulents helped reduce fire hazards by keeping thatch moist via root networks that snuff out embers after lightning strikes. Their ability to live here in straw over a long time without soil led to their oldest name, “live forever,” the literal translation of sempervivum.
Sempervivums are rosette-shaped, ranging from an inch across to much larger individuals. The traditional use of sempervivums is in rock gardens tucked into gaps to hold the earth in place with their dense coverage. As they age they'll spread via offsets into ever larger patches of plants. Those such as Sempervivum arachnoides produces its white webby offsets on the end of long stems that allow it to dangle off stone faces for a waterfall of color.
The most popular way to grow them in cold climates is in heavy stone troughs and bowls able to stand out in the winter cold. These are usually set onto walls or pedestals to bring the miniature sedums and others up to eye levels to better appreciate their geometry, flowers and textures. More recently the sempervivums are creeping into small tray or dish gardens for patio or indoors blended with less hardy accent succulents. Often these are mixed into sparkling natural minerals, glass balls and colored gravels to create really lovely small compositions. These are among the most beautiful winter holiday creations to enjoy indoors, on a sun porch or even outdoors provided they are in a container that won’t be destroyed by cold.
You can buy sempervivums without knowing their actual varietal names if you grow them in pots that won’t be out in the frosty air. Shopping for plants by visual interest ensures you pick the ones most exciting to your eye. However, when growing sempervivums outdoors, know some varieties are hardy to zone 4, while others zone 7, so it’s important to choose a variety known for its cold hardy vigor. The best part about introducing a new succulent plant to your garden is the ease of propagation. That original becomes the mother of many babies when you sever and root offsets into a new freestanding plant.
It’s easy to get started with sempervivums come spring because you don’t have to worry about those last late frosts. Above all, know the Atlas Mountains are dry and soils extremely well drained so these plants demand similar conditions in pots. Use cactus potting soil or make your own by mixing sharp sand with equal parts quality potting soil for the optimal balance between drainage and fertility.
With hardy succulents, cold climate gardeners can still enjoy the exciting new look without concern for frost. Grow in rocks, pots or anywhere elevated enough to ensure perfect drainage for jewel box beauty that lives forever outdoors, just as nature intended.
Maureen Gilmer is an author, horticulturist and landscape designer. Learn more at www.MoPlants.com. Contact her at firstname.lastname@example.org or P.O. Box 891, Morongo Valley, CA 92256.