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Planting and clearing for fire safety in brushy hillside areas.

Summer's end. In northern California's hillside communities, that means conditions may be ripe for wildfires. Temperatures hover in the 80s and 90s, humidity is low, and the golden grasses that grew high following last winter's rains now stand like so many dry, waving fuses.

Although wildfires are not the regular occurrences here that they are in Southern California, where each year moisture-wicking Santa Ana winds blow off the deserts and across the volatile, chaparral-blanketed hillsides (as in the picture above), they can be troublesome. Already this year, crackling-dry grasses have gone up in flames on hillside of South San Francisco, east of Chico, and in other areas of northern California--threatening houses in some areas.

What can hillside homeowners do to protect their houses and their communities from fast-moving wildland fires?

The first line of defense is to change the landscape around the house to be less combustible and more defensible. Thin out highly flammable native brush beyond the garden to reduce vegetative fuel loads, maintain an irrigated greenbelt, and plant low-fuel-volume, deep-rooted, and drought-tolerant ground covers between the garden and chaparral--see plant list beginning on page 164. You'll also want to 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-come winter rains will help speed the establishment of new plants and reduce your watering duties. (Before you clear and plant on very steep slopes, check with a landscape architect, soil consultant, or your building or fire department.) How to use plants to create fire-defense zones around your house

The landscape within 30 feet of your house is the most critical area for fire safety. In this zone, a nonflammable landscape might consist of lawns, flower and vegetable gardens, shrub borders clipped lower 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 the chimney.

From 30 to 100 feet away (this may take you into a neighbor's property or onto public land), low-growing greenbelt plants are the answer. Remove large shrubs that are within 18 feet of each other. Prune back the remaining shrubs by at least 50 percent to reduce the amount of dead material and burnable leaves and stems.

From 100 to 200 or more feet away from the house, cut back native woody chaparral yearly. If possible, remove or thin highly flammable natives such as California sage brush and chamise (also called greasewood). These plants contain lots of fine, dry dead leaves and have very oily stems and leaves. Planting for fire safety: ground and slope covers

With enough heat, any plant will burn--but plants differ in how hot they burn, how high a flame they produce, and how fast they cause a fire to spread. An effective 2-foot-tall free-retardant ground cover on a slope fanned by dry, 30-mph autumn winds will produce a flame only 10 feet high. Under the same conditions, a less fire-retardant ground cover 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 fuel to a fire, and even slow its advance. Plants on steep slopes must have deep roots to prevent surface erosion and landslides. Also, choose drought-tolerant plants and water them occasionally through the summer.

Succulents. These plants have the greastest fire retardance, and they're drought tolerant. But they're not very deep-rooted. Use them in full sun on falt land or shallow slopes (30 percent at most). 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. Remove dead thatch.

White trailing ice plant (Delosperma alba). Grows 6 to 8 inches tall 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). Perhaps the best ice plants for fire retardance, erosion control. D. floribundum grows to 6 inches, D. hispidum to 24 inches. Remove dead thatch 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. The first four listed here are good for shallow slopes (not steeper than 30 percent).

Carpet bugle (Ajuga reptans). Grows 3 to 12 inches tall; spreads quickly. It's a good choice for under trees, or in small, shady areas. Needs more water and fertilizer than other listed plants. Very hardy (0[deg.] or colder).

Wild strawberry (Fragaria chiloensis). Forms low, compact mats 6 to 12 inches tall with dark, glossy green leaves. Needs regular summer water, sun or part shade. Hardy to 15[deg.].

Trailing gazania (G. rigens leucolaena). Beautiful silver-gray foliage and 2- to 3- inch yellow or orange flowers; grows 6 to 10 inches tall. Stems spread. Give it full sun; water sparingly. Hardy to 20[deg.].

Thyme (Thymus praecox arcticus, T. pseudolanuginosus). Grows 2 to 6 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 60 percent). Give them full sun, except as noted.

Myoporum parvifolium (M.p. 'Prostratum'). Bright green leaves densely cover this 3-inch-tall ground cover; white flowers appear in summer. It may die back in three to five years. Hardy to 20[deg.].

African daisy (Osteospermum fruticosum). Grows 6 to 12 inches tall; runners spread 3 to 4 feet a year. White or purple flowers appear in winter, spring. It's good for erosion control. It looks best with summer water. Cut back every two to three years. Hardy to 20[deg.].

Santolina (S. chaemaecyparissus, S. virens). These grow 24 inches tall but are best looking if kept at 12 inches or lower. Foliage is gray or green; flowers are yellow or chartreuse. Hardy to 0[deg.].

Periwinkle, myrtle (Vinca major, V. minor). An excellent slope cover, it grows 6 to 24 inches tall and spreads by runners. Give it part to full shade, water in summer, and occasional feeding. Cut back when rangy. Hardy to 10[deg.].

Woody ground covers. If irrigated, these plants burn more slowly than 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 in high-mountain areas; it also performs well on the coast. Grows 12 inches 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 shrub grows 24 inches tall, 6 feet across, with a profusion of white flowers in late spring. Can control erosion. Give it full sun; cut back after flowering. Hardy to about 15[deg.].

Algerian ivy, English ivy (Hedera canariensis, H. helix). Ivies (especially Algerian) harbor snails, slugs, rats. Ivies like sun or part 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 tall with a 6-foot spread. Flowers come in many colors--pink, red, lavender, yellow, orange. Best in mildest climates. Plant in full sun; shear hard 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, 6 feet wide, and resprouts after burning (no need to replant). Leaves are small, bright green. Likes full sun, summer water, and any soil, dry to swampy. Hardy to 10[deg.].

Wild lilac (Ceanothus griseus horizontalis, C. gloriosus). Grows 12 to 24 inches tall; some kinds grow to 15 feet wide. Blue or white blossoms appear in spring. Deer love C. griseus horizontalis. Give full sun, and water sparingly in summer to avoid root rot. Short-lived plants (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 flowers appear in spring. Plant in full sun, feed and water sparingly, and thin every two to three years. Proper care for trees in fire-area landscapes

Important in any landscape, trees are particularly valuable on steep hillsides. The roots of many trees go much deeper (sometimes 15 feet or more) than those of most ground cover plants. Extra-deep-rooted trees can help to prevent or lessen the severity of landslides. On the negative side, trees contain a large amount of burnable wood and leaves. Highly flammable trees should never be planted in high-fire-danger areas: avoid pines and junipers (small, oily leaves and stems) and most of the eucalypts (high in oils, and many kinds drop tinder-like shreds of bark).

Trees that resprout after burning are generally your best choices: you don't have to replant them, and their roots continue to anchor the soil. California live oak (Quercus agrifolia) and valley oak (Q. lobata) are perhaps the most fire resistant. Other good choices are alders (Alnus species), sycamores (Platanus), bottlebrush (Callistemon), black walnut (Juglans).

For fire safety, plant trees 18 feet or more apart, prune them high, and thin out dead undergrowth regularly.
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Date:Sep 1, 1984
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