Drought and Wildfire

The current Californian drought presents more problems than are apparent at first glance.

In addition to causing problems for farmers, trees and lawns, the drought is that it predisposes the state to more frequent and more intense wildfires.

Not All Forest Fires Are Created Equally

It is important to distinguish between the different types and spreading characteristics of wild fires, as each has a different effect on the forests.

Ground fires are usually of low intensity, and although they can deplete the rich leaf litter and nutrients of the floor, they are not as hazardous to mature trees. Ground fires burn fuels found below the surface litter.

By contrast, surface fires use fuels found on the surface of the ground, including leaf litter, pine needles, bark, twigs, and fallen branches. Surface fires are of higher intensity than ground fires are, yet they are not as intense as crown or canopy fires. Crown fires are incredibly intense, but they typically require strong winds and plenty of fuel to perpetuate.

Forest Fires Are Natural

Wildfire is a natural component of many western ecosystems, and most native plants and trees have evolved mechanisms for perpetuating the species despite the challenge. For example, giant sequoias (Sequoiadendron giganteum) and ponderosa pines (Pinus ponderosa) have evolved thick bark to help protect their trunks from the heat of forest fires.

Other trees, such as Jack pines (Pinus banksiana), have evolved cones that only open and release seeds once they are exposed to the high temperatures of a fire. By releasing their seeds at this time, the seeds find a bare forest floor, which they need not share with competitors. Many other trees, such as coast live oaks, depend in part on the caching habits of jays, squirrels and other creatures to ensure some of their acorns survive fires, and can sprout in the aftermath.

Paying for the Past

One factor that contributes to the danger of wildfires is the fire-suppression strategies of the recent past. Operating under a philosophy to suppress all wildfires, large amounts of fuel accumulated in the forests, as routine, low-intensity fires were not allowed to clear out this dead wood. Accordingly, when a fire does occur, this plentiful fuel can cause the fires to grow in intensity. Rather than a low-intensity ground or surface fire, a raging canopy fire develops, which kills a great number of trees – even those that are adapted to fire. Current strategies seek to allow low-intensity fires to burn in a controlled manner, which may help prevent canopy fires.

Special Species

Some trees are especially problematic during droughts. For example, coastal redwoods (Sequoia sempervirens), which typically grow in the fog-drenched coastal regions, often go into decline during droughts, and many die. When they do, they increase the chances of a ground fire – which are normally of low intensity – leaping into the canopy, courtesy of the trees’ dead foliage. Of course, many other species can also help fire to ascend into the canopy, but the size of redwoods increases the potential for problems.

Moving Forward

As reported by, California state officials have already documented more than 120 wildfires on National Forest land.  To help reduce the chances of severe wildfires in the future, the Forest Service is trying to restore the ecological balance of many areas. This includes, among other measures, removing invasive species and planting natives, many of which have evolved various forms of fire resistance.

Most scientists predict droughts to become more severe, more frequent and longer in duration as the Earth’s climate continues to change. These droughts are sure to cause an increase in the frequency of wildfires, while non-native species and past fire management strategies are likely to exacerbate the fires that do begin.

Therefore, while it makes good sense to do what we can on a local level to address these problems, such as thinning overcrowded forests, taking steps to conserve water and planting native species, it is going to require a global effort to address the problems of climate change, and the sequelae that follow.


Drought-Tolerant Trees

Drought is common throughout the history of the western United States, and it is only likely to become more common  in future. Accordingly, it is wise for Californians to select and plant drought-tolerant trees whenever possible. While now is not an ideal time to plant new trees, as new plantings require a fair amount of water to become properly established, most of these suggested species represent excellent choices, once the drought concludes.

Get to Know Your Natives

Because California has suffered droughts throughout the millennia, many of the state’s native shrubs and trees have evolved adaptations that enable them to survive long, dry periods.  Most of these are capable of surviving droughts once well established.

  • California redbuds (Cercis occidentalis)

  • California sycamore (Platanus racemosa)

  • Pacific wax myrtle (Myrica californica)

  • California bay laurel (Umbellularia californica)

  • Coast live oak (Quercus agrifolia)

  • Scrub oak (Quercus beberidifolia)

  • Valley oak (Quercus lobata)

  • Desert willow (Chilopsis linearis)

  • Hollyleaf cherry (Prunus ilicifolia)

Excellent Exotics

California is not the only place in the world with drought-tolerant trees, and many exotic species are equally suited for surviving low-water periods. While native trees are generally preferable to exotics, you can select some species that are unlikely to spread invasively or cause ecological problems.

  • Jujube tree (Ziziphus jujuba)

  • Kei apple (Dovyalis caffra)

  • African sumac (Rhus lancea)

  • Pomegranate (Punica granatum)

  • Olive trees (Olea europaea)

  • Japanese persimmon (Diospyros kaki)

  • Persian mulberry (Morus nigra)

  • Carolina laurel cherry (Prunus caroliniana)

  • Australian willow (Geijera parviflora)

  • Mulga (Acacia aneura)

  • Bailey acacia (Acacia baileyana)

  • Japanese Zelkova (Zelkova serrata)

  • Arizona cypress (Cupressus arizonica)

  • Honey locust (Gleditsia triacanthos)

  • Strawberry tree (Arbutus unedo)

  • Afghan pine (Pinus eldarica)

  • Bay laurel (Laurus nobilis)

Proper Establishment

In addition to selecting species suitable for drought-stricken regions, you must plant and establish them properly to give them the best chance for long-term survival. For example, when you water the newly planted trees, be sure to soak the soil deeply and infrequently. In contrast to frequent, shallow watering, deep, infrequent watering causes trees to develop deep root systems. These deep root systems enable trees to draw water from deep within the substrate during parched periods.

Further Reading

For more information on drought-tolerant trees, see these resources:


Helping Your Trees Survive the Drought

99.8 percent of California is suffering from some state of drought, and it is taking a toll on our trees.

Indeed, without concerted efforts, our state stands to lose much of its natural and urban forests. Unfortunately, the best thing for our trees – copious amounts of water – is not available. So, we must be creative, use our knowledge of tree biology and do what we can to give our trees the best chance of surviving this drought, and ensure they are in the best shape possible to withstand the next one.

Water Well

Use whatever water you have efficiently. Try to apply enough water to soak the upper 12 inches of soil, where most of a tree’s roots are located. Water the entire drip zone of the tree, but do not wet the trunk or surrounding soil excessively, as this may encourage bacterial and fungal growth. Do not spray the canopy of your trees with water as a significant portion of the water evaporates and never benefits the tree.

Prioritize Your Plants

When water is scarce, always allot the bulk of it to your trees. For one thing, your trees may take decades to replace, should they perish, while you can replace lawns and herbaceous ornamentals within a few months. The replacement value of trees is also considerably higher than the replacement cost and labor for most common ornamentals. So, if forced to choose between your oak trees and your rose bushes, water your oaks, sycamores and redbuds, but let the rose bushes die.

Lose the Lawn

Prioritizing your trees over your plants extends to the lawn. Not only is the water better allocated to your trees, but the lawn’s water needs are fundamentally different than those of your trees. Most mature trees desire infrequent, deep soakings, while grasses typically prefer frequent, light irrigation.

Frequent irrigation causes trees to develop shallow root systems. This not only causes stability problems, and predisposes the trees to failing in high winds; it prevents the trees from accessing deep water reserves. Many people are already making the switch from lawns to arid-adapted gardens or xeriscaping, which not only use less water, but they are better suited for living alongside your trees than a lawn is.

Mulch for Moisture

Mulch is an important tool for maintaining trees in wet periods; in droughts, it is indispensable. The mulch forms an insulating blanket over the roots, which keeps them from being scorched by the hot dry temperatures. Additionally, the mulch reduces the amount of water that evaporates from the soil, which keeps the soil damper than it would be without the mulch. Do not place the mulch directly against the trunk of the tree. Place a 2-inch-thick layer nearest the trunk, increasing to a 4-inch-thick layer near the drip line.

Get Creative

Try to collect and store as much water as possible, which you can use to water your trees. While it may be difficult to collect enough water to water a large, mature tree, scrounging for water can help you accumulate enough water to keep young trees healthy. Consider collecting gray water from your home or installing a rain cistern. When you use water for unusual tasks – such as filing a child’s swimming pool or changing the water in a freshwater aquarium – try to discard the old water inside the drip line of your young trees.

Going Forward

Use caution when deciding to plant new trees during droughts. It can be done, but young, yet-to-be-established trees require consistent watering to keep the root zone damp. If you decide to plant new trees, be mindful of the fact that the next drought may be right around the corner. Avoid planting trees that – even during wet periods — require supplemental watering, such as redwoods (Sequoiasempervirens) and red maples (Acer rubrum). Magnolias (Magnolia ssp.), cherry trees (Prunus spp.), birches (Betula spp.), gum trees (Eucalyptus spp.) and bald cypresses (Taxodium distichum) also require more moisture than Mother Nature provides to southern California.

Further Reading

See the following resources to find more information on keeping your trees healthy during the drought:

Drought Causes Tree Death and Limbs to Fall

Tyler State Park in East Texas has seen an increase in trees dying, due to drought in the region. Although more trees are dying, the state park says that it has been difficult keeping up with the necessary tree maintenance and removal because the state legislature took away some of their funding this year. An estimated 250 dying trees have been cut down in the park from about April through June to keep campers safe.

One tree that was not cut in time dropped a large limb onto an RV in the park. Neal Williams, his wife, and two grandsons were asleep in the RV at the time the branch fell. Although they were uninjured, the RV suffered minor damage. Williams and park officials were surprised that the limb fell in calm weather from what appeared to be a healthy tree.

Tyler State Park Superintendent, Bill Smart, says, “Since most of the trees die in winter, we don’t know until spring when the trees were supposed to come back and out, and they weren’t coming back out.” Smart warns that although they are doing the best they can, they need people to be aware of the condition of the trees and of the possibility of limbs falling.