| A Look at Plants That Act as a Fire Barrier |
Master gardener Maureen Gilmer, host of Weekend Gardening, explains how succulent plants can act as a fireproof barriers.
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By Maureen Gilmer
Sept. 24, 2007 — Live under a thatch roof, and you live in fear of fire. For the ancients, lightning strikes could turn a sizable cottage into an instant fireball. When thunder rolled through dark skies, they would turn for help to the gods of these heavenly events, Thor or Jupiter. And nothing protected the thatch rooftop quite like the plants devoted to them. One 16th-century author wrote, "Old writers do call it Jovis barba, Jupiter's Beard, and hold the superstitious opinion that in what house so ever it groweth, no lightning or tempest can take place to do any harm there." Jupiter's beard refers to the tiny sempervivums and their nearly identical but less-hardy brothers, jovibarba. These genera of cold-hardy succulent plants are native to the alpine regions of the French and Italian Alps. But they have been naturalized in Canada and New England as well, attesting to a remarkable ability of succulent flesh to survive intense cold. To this day eastern Europeans still plant these little succulents on their rooftops, which has earned them the name, houseleeks. While it may seem to be a purely superstitious practice, there is logic here. A rooftop cloaked in colonies of succulent plants that contain high moisture content would act as a fireproof barrier. Sparks or embers from a strike would not find a combustible surface there. In very old thatch homes the mats of sempervivums would grow throughout the entire surface, adding insulation, binding disintegrating straw and protecting from chimney sparks. The succulent's unique ability to rapidly absorb moisture would intercept rainwater that might seep into the home below. In short, succulents on the roof made sense. These beautiful rosette-shaped succulent plants are exceptional choices for northern gardeners. Combined with the sedum clan, they present a palette of lively plants that bloom exceptionally whether on a roof or in the ground. Rocky mountain cliffs as well as tile roofs illustrate their cultural preferences, which is express drainage, marginal fertility and plenty of sun. The one Achilles' heel of this and all succulents is standing water and saturated soils. Therefore it is always best to err on over-dry conditions than risk over-wet ones. Sempervivums produce rosettes of symmetrical, tightly packed leaves that give them a uniquely geometric look. Each rosette will produce "chicks" that surround the mother, creating an ever-larger clump. The mother rosette is monocarpic, which means she will bloom once then die, leaving a gap in the center of her chicks. Some gardeners add coarse sand to the gap to protect the newly exposed stems and tidy up its appearance. In the meantime, the chicks will mature, each becoming a mother and so on. It's easy to propagate your sempervivums by severing the stem of a chick. Allow the tip to dry out a day or two, then stick it in moist sand. Roots quickly develop rendering this chick into a brand new mother. Ease of propagation makes these succulents popular among collectors who trade chicks for new varieties. The most traditional way of planting these sempervivums and their kin is in stone troughs. They can go in-ground, provided the soil is elevated and well drained. They are often found in rock gardens and along disintegrating rock walls where they spring from nooks and crannies. Learn more about them and see pictures of various cultivars at www.succulent-plant.com/sempervivum.html. Sempervivum is the most common gateway plant to the fascinating world of cold-hardy succulents. For those in cold-weather regions longing to dabble in the succulent forms sweeping the modern design world, the plants of Jupiter are the right choice. (Maureen Gilmer is a horticulturist and host of Weekend Gardening. E-mail her at mo@moplants.com. For more information, visit: www.moplants.com. Distributed by Scripps Howard News Service.) | Get DIY On Your TV. Just follow the instructions to see if DIY Network is available through your cable or satellite provider. |
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