Use this list to identify Marin's most common fire-prone plants. These plants ignite readily and burn intensely, and should be avoided (or removed, if noted) if present in a home's Defensible Space zone or close to roads and driveways. If removal is not an option, intensive maintenance may be required to reduce flammability. Your fire department may require removal of the plants on this list within 100' of structures.
This list is not comprehensive and is intended to identify only the species most common in Marin. Learn more about fire-prone plants.
Acacia melanoxylon (Black Acacia) is very quick-growing tree to 40 feet tall or much more with a 20 feet wide and in maturity an oval shaped crown. It has rough dark gray bark with vertical fissures and mid-green leaf-like flattened stems, called "phyllodes", that are 3 to 5 inches long by about an inch wide with one margin straight and the other curved. Small creamy flowers are in a small ball-like cluster from late winter into spring and are followed by thin curling seed pods that hang in brownish sheaves. A durable tree for quick growth, screening and erosion control, however its fire prone nature makes it unsuitable for WUI locations in Marin. The aggressive roots can lift sidewalks, damage foundations and plumbing and together with leaf, seed pod and branch litter and its propensity to sucker and reseed, makes this tree not ideal for street plantings or near living areas.
Thuja is a genus of coniferous trees in the Cupressaceae (cypress family). There are five species in the genus, two native to North America and three native to eastern Asia. The genus is monophyletic and sister to Thujopsis.
They are commonly known as arborvitaes, (from Latin for tree of life) thujas or cedars.
Thuja are an extremely fire prone species, and shoud not be planted in the defensible space zone or near driveways or roadways.
Umbellularia californica is a large hardwood tree native to coastal forests of California and slightly extended into the state of Oregon. It is endemic to the California Floristic Province. It is the sole species in the genus Umbellularia.
The bay tree, like so many others, will develop differently depending upon the conditions in which it is growing. When found on drier hillsides, it is generally smaller, with yellower leaves and smaller nuts. In a canyon with its roots in plentiful water and rich soil, the leaves will be thinner and darker green and whole tree, nuts and leaves will generally be larger.
Because of its thin bark, the tree is easily top-killed by fire, but it sprouts rapidly. Dense clumps are often formed on cutover land, which may prevent the establishment of desired conifers.
Baccharis pilularis, called coyote brush (or bush), chaparral broom, and bush baccharis, is a shrub in the daisy family native to California, Oregon, Washington, and Baja California. The plants are found in a variety of habitats, from coastal bluffs, oak woodlands, and grasslands, including on hillsides and in canyons, below 2,000 feet (610 m).
Coyote brush is known as a secondary pioneer plant in communities such as coastal sage scrub and chaparral. It does not regenerate under a closed shrub canopy because seedling growth is poor in the shade. Coast live oak, California bay, Rhus integrifolia, and other shade producing species replace coastal sage scrub and other coyote bush-dominated areas, particularly when there hasn't been a wildfire or heavy grazing.
In California grasslands, it comes in late and invades and increases in the absence of fire or grazing. Coyote bush invasion of grasslands is important because it helps the establishment of other coastal sage species.
They are evergreen trees or large shrubs. The leaves are scale-like, arranged in opposite decussate pairs, and persist for three to five years. On young plants up to two years old, the leaves are needle-like. The cones are long, globose or ovoid with four to 14 scales arranged in opposite decussate pairs; they are mature in 18-24 months from pollination. The seeds are small, 4-7 mm long, with two narrow wings, one along each side of the seed.
Many of the species are adapted to fire, holding their seeds for many years in closed cones until the parent trees are killed by a fire; the seeds are then released to colonise the bare, burnt ground. In other species, the cones open at maturity to release the seeds.
The fast-growing hybrid Leyland cypress, often found in gardens, draws one of its parents from this genus (Monterey cypress C. macrocarpa).
Eucalyptus globulus, blue gum eucalyptus, is a tree that is not native to California. It is an invasive plant that was introduced from Australia and naturalized in the wild. The California Invasive Plant Council (CAL-IPC) classifies the most common blue gum eucalyptus as a moderate invasive because the trees need certain conditions to thrive.
All eucalyptus species are prone to fire, and should be removed or require significant maintenance within 100' of structures to reduce wildfire hazards.