The key to recognizing which plants could put your home at a greater risk is to “think” like a wildfire. Survey your landscape and see if you can spot any plants that would be great for kindling — dry grasses, trees with peeling bark or shrubs that have dried to thickets — or plants that are oil-rich and easily combustible. These are all plants you want to avoid in a fire-smart landscape.
3 Categories of Plants to Avoid for a Fire-Wise Landscape
1. Plants that accumulate dead material. A wildfire can quickly race through a landscape strewn with fallen leaves and needles, dead plants and dry grasses. In gardens, avoid plants that have characteristics like peeling bark, frequent leaf drop or the tendency for dieback.
Staying on top of maintenance is crucial and can turn a “high-risk” plant into a “lower-risk” plant. For example, twiggy perennials, such as native California buckwheat, make excellent drought-tolerant garden plants and don’t present an above-average fire risk if maintained properly. If neglected, California buckwheat and many other woody perennials have a tendency for dieback, often hidden between an exterior of green leaves. A twiggy, dead interior on any plant can be highly flammable but is preventable through frequent cutting back.
Plants to watch out for: Ornamental grasses, eucalyptus, bamboo, coyote bush (Baccharis spp.), California buckwheat (Eriogonum fasciculatum), coastal sagebrush (Artemisia californica), palms, pampas grass, scrub oaks (Quercus spp.) and others
2. Plants that are high in oil or resin. If you’ve ever tossed a sap-covered pine log in a fire, you know just how flames respond to resin. Not only do flames burn hot and quickly through resin-rich wood, they can also “pop” and send sparks flying — a dangerous combination for fire spread. Avoid planting plants rich in resin, gum or oil in fire-risk areas.
If you have pines or other conifers growing in your yard, make sure you keep them properly maintained by pruning to thin branches regularly and sweeping up fallen needles. To prevent fire spread, it is not recommended to plant conifers within tree-fall distance of a building.
Plants to watch out for: Pine, juniper, cedar, cypress, fir, spruce, eucalyptus, California bay, yew and others.
3. Plants that have low moisture content in leaves. Plants with moisture-rich leaves are slower to ignite than plants that naturally hold less water in their leaves. Deciduous trees usually have a higher moisture content in leaves than do evergreens and some small-leafed trees.
The dry leaves and hollow stems of bamboo — technically a giant grass — can easily ignite in a wildfire. Keep bamboo away from buildings, or avoid planting altogether, in areas with fire risk. For bamboo, trees and shrubs, remember to keep leaf litter picked up to avoid buildup of a highly flammable material.
Eucalyptus trees are a triple fire threat: The plants accumulate dead material, all parts of the plant contain resins and the leaves are less moisture-rich than deciduous trees. Fire Safe Marin, a California nonprofit, advises homeowners in at-risk areas to remove or intensely maintain (thin, prune and remove detritus) eucalyptus trees within 100 feet of structures to reduce fire hazard.
Plants to watch out for: Acacia, bamboo, eucalyptus, Scotch broom (Cytisus scoparius), common gorse (Ulex europaeus), larch and others.
Many types of plants are flammable if not properly maintained, but the risk of any given plant can be reduced if it’s well-watered and pruned free of dead materials. If you live in an at-risk area, stay on top of garden chores like cutting dead branches, keeping grasses and woody perennials trimmed and sweeping up fallen leaves and needles. If there is a fire warning, make sure all plants are given a deep-soak watering.
Plants with a high water content — such as succulents and cactus — and a variety of low-risk trees, shrubs and perennials can help prevent the spread of fire through a landscape. Maintenance is key, even with lower-risk fire-smart plants, as is planting in zones of safety.
It’s also recommended to check region-specific fire safety guidelines from your county fire department. For more information on fire safety, check out resource pages on the Cal Fire and Fire Safe Marin websites.