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
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
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
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
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
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
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
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
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
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.