One of the most appealing aspects of living in a dry climate is the extended time throughout the year to enjoy your outdoor living space—the pool, patio, and grill. But for many who reside in these regions, the threat of wildfire is very real, fueled by drought or strong winds.
If you live in an area at risk for wildfires—like Southern California or much of the West—you may have heard of certain plants that are fire-resistant. It makes sense to take measures to landscape your property with shrubs, trees, perennials, and succulents that may, in some cases, possibly save your house from burning down.
But what about the most flammable plants—the ones you should consider removing or at least not planting? These plants are known for the amount of dead fuel that accumulates inside them, high oil (or high resin), or the low moisture content of their leaves and branches.
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Characteristics of Flammable Plants
All plants are flammable if not pruned periodically. The risk associated with any one plant can be greatly diminished with regular maintenance. Highly flammable plants can ignite quickly, releasing lots of heat, even if they are healthy and well-watered. In areas experiencing drought, even moderately flammable plants can become more prone to ignite.
Characteristics of highly flammable plants include:
- Dry and dead leaves or twigs
- Dry, leathery leaves
- Abundant, dense foliage
- High oil or resin including gums or terpenes
- Shaggy, rough, or peeling bark
- Lots of dead leaves underneath the plant (litter)
- Needle-like or very fine leaves
- Foliage with low moisture
The following list of flammable plants was created from information provided by various fire agencies, and botanical organizations throughout the United States. They are presented in alphabetical order.
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- Botanical name: Acacia species
This striking tree and shrub are native to tropics or warm areas of the world, including Australia, Mexico, and the southwestern United States. The leaves from some species of Acacia contain resin and flammable oils, which can encourage fires.
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- Botanical name: Hedera canariensis
This particular ivy was planted in the mid-1900s because it is a fast-growing ground cover that can quickly cover bare spots on hills, and pretty much everywhere else. Its invasiveness—it attaches firmly to surfaces like walls, fences, and arbors—has made it despised by some and considered a deep-rooted weed, spreading, and hard to get rid of.
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- Botanical name: Bambusa
While bamboo makes a great privacy screen and creates an exotic, tropical look in a landscape, they are flammable. These giant grasses are spread by underground stems (rhizomes) into two types: running and clumping. Since they are tall, dry, and grow close together, bamboo can quickly spread a wildfire.Continue to 5 of 22 below.
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- Botanical name: Cytisus
French, Spanish and Scotch brooms are invasive perennials that spread easily and are extremely flammable because of their oil content.
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- Botanical name: Adenostoma fasciculatum and A. sparsifolium (red shanks)
Also known as greasewood and native to California, both of these chamise shrubs thrive in full sun, dry climates, and will grow in poor, rocky soils. Identifiable by their needle-like leaves with tiny clusters of white flowers. Older stems can get woody and create very hot fires if ignited.
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Cypress trees and shrubs that are especially flammable include:
- Arizona cypress (cupressus glabra)
- Italian cypress (cupressus sempervirens)
- Leyland cypress (cupressocyparis leylandii)
- Tecate cypress (cupressus forbesii)
While these evergreen trees are useful as screens, hedges or windbreaks, they are strongly scented and can become tall torches during wildfires.
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- Botanical name: (Pseudotsuga menziesii)
If the name sounds somewhat familiar, that's because young Douglas firs are often cut for Christmas trees. Needles on these trees have a sweet fragrance when crushed or stepped on. The thin, resinous bark of young Douglas firs makes them highly susceptible to wildfires.Continue to 9 of 22 below.
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Eastern Red Cedar
- Botanical name: Juniperus virginiana
This conifer grows into a shape that resembles an inverted pyramid with branches that grow outward and upward. Although it grows in most USDA zones, this particular species has been a threat to Oklahoma and other Western states, contributing to wildfires, drought, and loss of cattle-grazing land.
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- Botanical name: Eucalyptus camaldulensis
Also known as red gum or river red gum, these strongly scented Eucalyptus trees contain highly combustible oils produced by the leaves. Leaf litter is high in phenolics, which prevents breakdown by fungi and accumulates as large amounts of dry, combustible fuel.
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- Botanical name: Dictamnus albus
One of its other common names, burning bush, is a blazing tip-off that this shrub might be flammable. Also known as fraxinella or dittany, this plant's glossy olive-green leaves are attractive throughout the growing season. When rubbed or brushed against, the plant emits a strong lemony scent. Oils from immature seed capsules may ignite if a lighted match is held underneath a flower. In hot, dry weather, Dictamnus can easily catch fire, which has led comparisons to the burning bush referred to in the Bible.
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- Botanical name: Lonicera japonica
Lonicera is loved for its fragrant flowers that are tubular or trumpet in form. Flowers attract hummingbirds, and the red and purple berries that follow are a good source of food for a variety of birds. Once valued as a shady ornamental plant, it was often planted around porches. However, Japanese honeysuckle is invasive and highly flammable.Continue to 13 of 22 below.
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- Botanical name: Juniperus virginiana
Junipers are conifers and generally are easy to care for: they are drought tolerant and will grow in any type of soil if there is drainage. They also do not require lots of maintenance and pruning, maybe every few years or so.
Several varieties contain highly flammable resins. Junipers can accumulate dead leaves, and as they age, they become more prone to easily ignite. Some firefighters nickname them "gasoline plants".
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- Botanical name: Miscanthus sinensis
Native to Korea, Japan, China, and Taiwan, these ornamental grasses are clump-forming, showy, and range from dwarf types to large varieties. Although it doesn't require pampering and lots of maintenance, this grass, also known as Eulalia or Japanese silver grass, becomes dried and if not pruned is especially flammable. If you live in an area prone to wildfire, cut these grasses back in late winter to early spring.
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- Botanical name: Arctostaphylos hookeri
Native to the Far West, Manzanita is a chaparral plant that can grow very dense. All varieties can be identified by their small, urn-shaped white or pink flowers that appear in late winter to early spring. While these ground covers, shrubs, and trees benefit wildlife—butterflies and hummingbirds are attracted to those flowers and the berries that follow—they may be one of the most fire-prone types of plants. Dry, deadwood becomes highly flammable.
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- Botanical name: Melaleuca
These Australian native trees have needle-like leaves and flowers that resemble those of the bottlebrush shrub and attract birds. While they are admired for their drought tolerance, and fast growth, the oils in melaleuca's leaves and bark make them flammable. Those oils are the same ones used for medicinal and healing purposes as tea tree oil, which is applied topically.Continue to 17 of 22 below.
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- Botanical name: Palmus
Palms are tropical and subtropical trees that are extremely popular in the Mediterranean and dry landscaping. Unfortunately, palms are dangerous during wildfires for a few reasons, including:
- Dried and dead palm fronds become like flaming arrows if they detach from their trunks and are carried by winds.
- Embers can become embedded into the fibrous tissue, leaf bases, or along the trunk of a palm tree. The result: a palm that can rapidly become engulfed in flames, spreading to other plants and structures nearby.
Certain species of palm trees can be hazardous in fire-prone regions, especially if they are not maintained (pruned) or because of their form. Palms with fibrous tissue or leaf stem bases along the trunk should be 30 or more feet from a home or structure.
Species to Avoid
- Mediterranean fan palm: Chamaerops humilis
- Canary Island date palm: Phoenix canariensis
- Date palm: P.dactylifera
- Senegal date palm: P. reclinata
- Pygmy date palm: P. roebelenii
- Windmill palm: Trachycarpus fortuneii
- Mexican fan palm: Washingtonia robusta, has a leaf stem base that makes it catch fire and spread quickly.
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- Botanical name: Cortaderia selloana
A native to Argentina, pampas can grow as tall as 20 feet and 12 feet wide. Although its feather-like plumes are popular in floral arrangements, in many regions, pampas are considered a weed and are not available in nurseries. Easily spread by seed, pampas often grow in wildfire areas, and can quickly ignite and spread, especially if it is dried out.
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- Botanical name: Pinus
Flammability varies by species, but younger trees are more susceptible. Pines can be easily killed by fire due to thin bark, relatively flammable foliage and accumulation of dead lower branches. Pine trees' needles and resin are both highly flammable, and extreme heat and drought make them more likely to ignite.
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- Botanical name: Rosmarinus officinalis
A pretty, fragrant groundcover and shrub that grows in Mediterranean climates. Over-watering and heavy feeding results in poor growth, followed by a woody plant. Light pruning or tip-pinching keeps it healthy. Keep in mind that this drought-tolerant herb contains flammable oils.Continue to 21 of 22 below.
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- Botanical name: Arborvitae
Thuja or thuya are symmetrical shrubs and trees that are often trimmed into geometrical shapes, like cones, cylinders, and globes.
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- Botanical name: Heteromeles arbutifolia
Commonly known as California holly, the leather leaves of a Toyon shrub make it highly flammable.