Long Live the Sempervivums!
First published on garden.org on May 11, 2006, by Suzanne DeJohn
What's not to love about a plant whose name translates to "always alive?" Sempervivums (semper, meaning "always," and vivo, meaning "alive") are commonly called hens-and-chicks, for obvious reasons, and houseleeks, for obscure ones. Whatever you call them, these charming succulents are remarkably durable and surprisingly prolific.
Native to the mountains of central and southern Europe and the Mediterranean islands, sempervivums form low-growing rosettes of pointed, fleshy leaves. They propagate by forming new plants ("chicks") at the end of long stolons. A single mother plant (the "hen") can colonize a rocky crevice in a remarkably short time. I set one small rosette on just a trace of soil in our stone wall, and it has filled the space in less than one year -- with no supplemental water or fertilizer.
In fact, overwatering and overfertilizing spell trouble for sempervivums. These durable little plants thrive on neglect. It's hard to believe they can grow so well with so little to work with -- some sunshine and whatever water and nutrients they can gather from their rocky perch. On the other hand, such meager surroundings mean they have little in the way of competition from other plants. Mother Nature has her ways, and it pays us gardeners to heed her.
In their alpine habitat, sempervivums are often found growing in rocky crevices. So, excellent drainage is a must, and a niche in a stone wall or rock garden is a perfect site. Set in rich, damp garden soil, the plants will likely suffer from rot or be overrun by more vigorous plants.
Sempervivums thrive in shallow containers -- dish gardens -- filled with gravelly soil. Plant a few different varieties or mix with other drought-tolerant succulents. Because they readily hybridize, breeders now offer them in a range of colors, from yellow to gray to lavender. The plants thrive in full sun, although some cultivars hold their color better with some afternoon shade.
After a few years, individual rosettes will form flowers, which are usually red, purple, or yellow. The rosette dies after flowering but, hopefully, it will have formed plenty of chicks before it does. Detach extra chicks and set in a new spot so they can form more colonies.
The Romans cultivated sempervivums on rooftops to guard the house against lightning. In Scandinavia, they were thought to drive off demons. Today, sempervivums are among the succulent plants favored for use on green roofs -- roofing systems that incorporate plants in their structure. The benefits of green roofs include reduced water runoff, sound insulation, and bird and insect habitat. But I have yet to find mention of the lightning or demon protection offered by sempervivums in the green roof literature.
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