Trees that Resist Wildfires
Edited by Len Phillips
This is the last in a series of articles that Online Seminars has been running about how to lessen the damage to trees and landscapes that occurs during a natural disaster. The United States has approximately 700 million acres of forests. These forests are very important for maintaining ecological balance as well as a stable economy.
Finding trees that resist wildfires is a challenge because trees are composed of wood that readily burns. Fortunately, some trees have actually adapted themselves to be protected against forest fires. The longleaf pine and the giant sequoia and some others have developed thick bark to resist the ravages of fires. These trees are called "pyrophytes," which means fire-traited plants. Other trees bear seed cones called "serotinous cones." These cones have seeds inside that are opened only by the intense heat of a wildfire. A serotinous cone, such as that of the lodgepole pine, can contain enough seeds to cover the forest with millions of seeds per acre for several years.
Some plants are more flammable than others. Evergreen conifers, such as juniper, pine, spruce, and cedar, are high in resins and waxes, the properties that keep them evergreen and durable. Unfortunately for each of these trees, the resins and waxes are highly flammable.
Fire Prevention around Homes
The top priority of a fire-dissuading landscape is to create a "defendable space". This is an area that will serve as a buffer zone should a wildfire approach a home. The goal is to keep a fire moving "slow and low" until it can be extinguished.
Highly flammable varieties should be removed from around a home. Replace them with deciduous plants. Deciduous plants retain more water in their foliage, which makes them much more difficult to ignite and burn. However, they also drop their foliage during the cool months and the dead leaves left on the ground may dry into a significant amount of combustible material. Picking up and composting or discarding freshly fallen leaves removes a source of ignition from around a home.
Avoid "ladder fuels". An example of this is a burning, dry, ornamental grass that ignites a taller shrub that allows the flames to jump up to some pine branches, which then jumps up to the roof. The goal of a fire wise landscape is to hold the fire on the ground and out of a tree's canopy.
Ideally, garden designs should consist of islands in the yard with an interesting plant mix and hardscapes separating one garden from the next. The hardscape can be a driveway, patio or rock lawn. This technique also allows firefighters some precious space between gardens should they have to fight the flames.
There are also measures that an arborist can take to plant trees in a manner that will minimize the damage that might occur during a wildfire. For example:
- Plant trees that have a low surface area to volume ratio, such as plants with thick, broad leaves instead of those with narrow, needle-like leaves.
- Plant trees that have a high moisture content, as found in succulents and other plants with fleshy foliage.
- Plant trees that will have a low percentage of dead matter or debris in their crowns and keep the forest floor clear of unnecessary flammable material.
- Plant trees that are drought tolerant or keep them irrigated so they do not have a low moisture content especially when the likelihood of a wildfire is high.
- Select trees that grow well in the local climate and soil type.
- Select trees with an open, loose branching habit so the fire can not jump from one branch to the next.
The overall goal is to keep in mind that all trees are flammable under certain conditions. Care should be taken to lessen factors that contribute to their flammability and hazard.
Developing lists of trees that resist wildfires have been prepared by twenty state Cooperative Extension Service offices around the U.S. The following list from Maryland seems pretty typical. For a complete listing, visit the Fire wise Communities Program website. These sources are science-based, consistent with Fire wise principles, and are updated periodically.
Trees that Resist Wildfires in Maryland
Scientific Name Common Name
Acer palmatum Japanese Maple
Acer rubrum Red Maple
Acer saccharinum Silver/River Maple
Acer saccharum Sugar Maple
Acer spicatum Mountain Maple
Aesculus hippocastanum Horsechestnut
Amelanchier canadensis Shadbush / Serviceberry
Betula nigra River birch
Betula papyrifera Paper/White Birch
Carpinus caroliniana Hornbeam
Carya illinoiensis Pecan
Carya tomentosa Mockernut Hickory
Castanea mollissima Chinese Chestnut
Celtis occidentalis Common Hackberry
Cercis canadensis Eastern Redbud
Chionanthus virginicus Fringetree
Cladrastis kentuckea Yellowwood
Cornus florida Flowering Dogwood
Cornus kousa Kousa/Chinese Dogwood
Crataegus spp. Hawthorn
Diospyros virginiana Persimmon
Fagus grandifolia American Beech
Fraxinus americana White Ash
Fraxinus pennsylvanica Green Ash
Ginkgo biloba Ginkgo, Maidenhair Tree
Gleditsia triancanthos var. inermis Thornless Honeylocust
Gymnocladus dioicus Kentucky Coffeetree
Halesia carolina Carolina Silverbell
Juglans nigra Black Walnut
Liquidambar styraciflua Sweetgum
Liriodendron tulipifera Yellow Poplar, Tulip Poplar, Tulip Tree
Magnolia acuminata Cucumber Magnolia
Magnolia virginiana Sweetbay Magnolia
Malus spp. Apples & Crabapples
Nyssa sylvatica Black Gum, Black Tupelo, Sour Gum
Oxydendrum arboreum Sourwood, Sorrel Tree
Platanus x acerifolia London Planetree
Populus grandidentata Big-Toothed Aspen
Prunus serotina Black Cherry
Prunus subhirtella Weeping/Rosebud Cherry
Pyrus communis Common Pear
Quercus alba White Oak
Quercus bicolor Swamp White Oak
Quercus coccinea Scarlet Oak
Quercus palustris Pin Oak
Quercus rubra Northern Red Oak
Salix babylonica Weeping Willow
Salix nigra Black Willow
Tilia cordata Littleleaf Linden
Ulmus americana American Elm
Viburnum prunifolium Blackhaw Viburnum
Zelkova serrata Japanese Zelkova
- The UC Forest Products Laboratory, "Vegetation Guide for Landscaping in High Fire Risk Areas", 1997.
- Lain, Ken, "Landscapes that Resist Threats from Wildfires", Watters Garden Center Blog, June 2013.
- Fire wise Communities, "Fire wise Landscaping and Plant Lists", 2013.
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