Summer’s end. In northern California’s hillsidecommunities, that means conditions may be ripe for wildfires.Temperatures hover in the 80s and 90s, humidity is low, and the goldengrasses that grew high following last winter’s rains now stand likeso many dry, waving fuses.
Although wildfires are not the regular occurrences here that theyare in Southern California, where each year moisture-wicking Santa Anawinds blow off the deserts and across the volatile, chaparral-blanketedhillsides (as in the picture above), they can be troublesome. Alreadythis year, crackling-dry grasses have gone up in flames on hillside ofSouth San Francisco, east of Chico, and in other areas of northernCalifornia–threatening houses in some areas. What can hillside homeowners do to protect their houses and theircommunities from fast-moving wildland fires? The first line of defense is to change the landscape around thehouse to be less combustible and more defensible. Thin out highlyflammable native brush beyond the garden to reduce vegetative fuelloads, maintain an irrigated greenbelt, and plant low-fuel-volume,deep-rooted, and drought-tolerant ground covers between the garden andchaparral–see plant list beginning on page 164. You’ll also wantto make sure that other exterior parts of the house are fire resistant,especially the roof. Fall is an excellent time to plan and plant a low-fuel-volume,fire-retardant landscape.
Still-warm temperatures and soon-to-comewinter rains will help speed the establishment of new plants and reduceyour watering duties. (Before you clear and plant on very steep slopes,check with a landscape architect, soil consultant, or your building orfire department.) How to use plants to create fire-defense zones aroundyour house The landscape within 30 feet of your house is the most criticalarea for fire safety. In this zone, a nonflammable landscape mightconsist of lawns, flower and vegetable gardens, shrub borders clippedlower than 3 feet, concrete or brick patios, and pools or spas.Don’t let trees hang over the roof or grow within 10 feet of thechimney. From 30 to 100 feet away (this may take you into a neighbor’sproperty or onto public land), low-growing greenbelt plants are theanswer.
Remove large shrubs that are within 18 feet of each other.Prune back the remaining shrubs by at least 50 percent to reduce theamount of dead material and burnable leaves and stems. From 100 to 200 or more feet away from the house, cut back nativewoody chaparral yearly. If possible, remove or thin highly flammablenatives such as California sage brush and chamise (also calledgreasewood). These plants contain lots of fine, dry dead leaves andhave very oily stems and leaves. Planting for fire safety: ground andslope covers With enough heat, any plant will burn–but plants differ in how hotthey burn, how high a flame they produce, and how fast they cause a fireto spread. An effective 2-foot-tall free-retardant ground cover on aslope fanned by dry, 30-mph autumn winds will produce a flame only 10feet high.
Under the same conditions, a less fire-retardant groundcover might ignite easily and produce 25-foot-high flames.Six-foot-tallc chaparral in 60 mph winds can send up 100-foot flames. The plants you choose for your landscape should provide little fuelto a fire, and even slow its advance. Plants on steep slopes must havedeep roots to prevent surface erosion and landslides. Also, choosedrought-tolerant plants and water them occasionally through the summer. Succulents. These plants have the greastest fire retardance, andthey’re drought tolerant. But they’re not very deep-rooted.
Use them in full sun on falt land or shallow slopes (30 percent atmost). All are hardy to 20[deg.] to 25[deg.]. Hottentot fig (Carpobrotus edulis). Grows 12 to 24 inches tall,spreads quickly to crowd out weeds. Pale yellow to rose flowers.
Removedead thatch. White trailing ice plant (Delosperma alba). Grows 6 to 8 inchestall with small, fleshy leaves; stems root quickly. For quick cover,set plants 12 inches apart. Remove dead stems and litter.
Rosea ice plant (Drosanthemum floribundum, D. hispidum). Perhapsthe best ice plants for fire retardance, erosion control.
D.floribundum grows to 6 inches, D. hispidum to 24 inches. Remove deadthatch occasionally.
Croceum ice plant (Malephora crocea). Grows 12 to 24 inches tall;trailing stems root. Produces reddish yellow flowers nearly year-round.Controls soil surface erosion. Remove dead woody material. Herbaceous perennials. If irrigated, these can slow a fire.
Thefirst four listed here are good for shallow slopes (not steeper than 30percent). Carpet bugle (Ajuga reptans). Grows 3 to 12 inches tall; spreadsquickly. It’s a good choice for under trees, or in small, shadyareas. Needs more water and fertilizer than other listed plants. Veryhardy (0[deg.] or colder).
Wild strawberry (Fragaria chiloensis). Forms low, compact mats 6to 12 inches tall with dark, glossy green leaves. Needs regular summerwater, sun or part shade. Hardy to 15[deg.]. Trailing gazania (G.
rigens leucolaena). Beautiful silver-grayfoliage and 2- to 3- inch yellow or orange flowers; grows 6 to 10 inchestall. Stems spread. Give it full sun; water sparingly. Hardy to20[deg.].
Thyme (Thymus praecox arcticus, T. pseudolanuginosus). Grows 2 to6 inches tall. Best used as a small-scale ground cover between rocks,in sun or part shade. Very hardy (0[deg.] or colder). The following four perennials are good on steep slopes (about 60percent).
Give them full sun, except as noted. Myoporum parvifolium (M.p.
‘Prostratum’). Bright greenleaves densely cover this 3-inch-tall ground cover; white flowers appearin summer. It may die back in three to five years. Hardy to 20[deg.].
African daisy (Osteospermum fruticosum). Grows 6 to 12 inchestall; runners spread 3 to 4 feet a year. White or purple flowers appearin winter, spring. It’s good for erosion control. It looks bestwith summer water. Cut back every two to three years. Hardy to20[deg.].
Santolina (S. chaemaecyparissus, S. virens). These grow 24 inchestall but are best looking if kept at 12 inches or lower.
Foliage isgray or green; flowers are yellow or chartreuse. Hardy to 0[deg.]. Periwinkle, myrtle (Vinca major, V. minor). An excellent slopecover, it grows 6 to 24 inches tall and spreads by runners. Give itpart to full shade, water in summer, and occasional feeding.
Cut backwhen rangy. Hardy to 10[deg.]. Woody ground covers. If irrigated, these plants burn more slowlythan wild chapparral. Deep roots help stabilize the steepest slopes;the first five are good on slopes to 60 percent.
Bearberry, manzanita (Arctostaphylos uva-ursi, A. hookeri’Monterey Carpet’). Bearberry is an excellent ground cover inhigh-mountain areas; it also performs well on the coast. Grows 12inches tall; roots as it creeps 12 to 15 feet wide. Full sun.
‘Monterey Carpet’ is hardy to 0[deg.], bearberry to -10[deg.].
Sageleaf rockrose (Cistus salviifolius). This wide-spreading shrubgrows 24 inches tall, 6 feet across, with a profusion of white flowersin late spring. Can control erosion. Give it full sun; cut back afterflowering. Hardy to about 15[deg.
]. Algerian ivy, English ivy (Hedera canariensis, H. helix). Ivies(especially Algerian) harbor snails, slugs, rats. Ivies like sun orpart shade; water and feed in summer. Hardy to 20[deg.]. Aaron’s beard (Hypericum calycinum).
This invasive spreader grows 12 inches tall; bright yellow, 3-inch flowers apper in spring.Plant in full sun; cut back in winter. Hardy to -10[deg.] or colder(semideciduous in coldest winters). Trailing lantana (L.
camara, L. montevidensis). Grows 2 feet tallwith a 6-foot spread. Flowers come in many colors–pink, red, lavender,yellow, orange.
Best in mildest climates. Plant in full sun; shearhard every two to three years. The following three plants will grow on near-vertical slopes.
Dwarf coyote brush (Baccharis pilularis ‘Twin Peaks’).This one’s unexcelled for erosion control; it grows 2 feet tall, 6feet wide, and resprouts after burning (no need to replant). Leaves aresmall, bright green. Likes full sun, summer water, and any soil, dry toswampy.
Hardy to 10[deg.]. Wild lilac (Ceanothus griseus horizontalis, C. gloriosus).
Grows12 to 24 inches tall; some kinds grow to 15 feet wide. Blue or whiteblossoms appear in spring. Deer love C.
griseus horizontalis. Givefull sun, and water sparingly in summer to avoid root rot. Short-livedplants (5 to 10 years). Hardy to 10[deg.]. Dwarf rosemary (Rosmarinus officinalis ‘Prostratus’).
This low grower (to 24 inches) spreads up to 9 feet; tiny blue flowersappear in spring. Plant in full sun, feed and water sparingly, and thinevery two to three years. Proper care for trees in fire-area landscapes Important in any landscape, trees are particularly valuable onsteep hillsides.
The roots of many trees go much deeper (sometimes 15feet or more) than those of most ground cover plants. Extra-deep-rootedtrees can help to prevent or lessen the severity of landslides. On thenegative side, trees contain a large amount of burnable wood and leaves.
Highly flammable trees should never be planted in high-fire-dangerareas: avoid pines and junipers (small, oily leaves and stems) and mostof the eucalypts (high in oils, and many kinds drop tinder-like shredsof bark). Trees that resprout after burning are generally your best choices:you don’t have to replant them, and their roots continue to anchorthe soil. California live oak (Quercus agrifolia) and valley oak (Q.lobata) are perhaps the most fire resistant.
Other good choices arealders (Alnus species), sycamores (Platanus), bottlebrush (Callistemon),black walnut (Juglans). For fire safety, plant trees 18 feet or more apart, prune themhigh, and thin out dead undergrowth regularly.
