In the aftermath of wildfire, many homeowners are alarmed by the sudden change in their landscapes and surrounding wildland vegetation. Many ask, “Will it grow back?”
Wildfire affects plants in a variety of ways. They can be completely or partially consumed, scorched, dried out or merely singed.
Fire impacts plant parts through:
- Leaf or needle scorch
- Root damage
- Trunk or branch damage
- Inner tissue (cambium) injury
- Bud death
Other, less direct, impacts include soil desiccation. Plants that can’t obtain adequate soil moisture after a fire are less likely to survive. Fire-damaged and water-stressed trees are also more susceptible to bark beetle attacks. However, many plants can recover after fire, depending on the intensity and duration of the burn and extent of dehydration. A plant that is stressed due to drought, injury, disease, insects or mistletoe is weak prior to a fire and unlikely to survive after a fire.
Plants vary in their response to fire. Fire readily kills some plants, rejuvenates others and some native plants have seeds that require fire to germinate. Some plants have the ability to resprout when the aboveground portion has been burned. Depending upon the species, sprouting can occur from the roots, base of the trunk, belowground root crown and grass crowns. Some resprouting plants include aspen, crabapple, birch, cottonwood, green ash, maple, willow, dogwood, wild rose, honeysuckle, desert peach, mormon tea, rabbitbrush and skunkbush sumac.
Some seeds may tolerate higher temperatures so they survive to grow a new generation. For some plants, the stage of growth determines the degree of damage. Most perennial grasses, for example, are more susceptible to fire damage when actively growing than when dormant. At the Caughlin and Washoe fire sites, the perennial grasses were dormant so now we are seeing new growth. Shrubs and trees starting to grow in the spring are more susceptible to fire damage than dormant plants. Often, plants of smaller stature survive fire because they contain less fuel and fire temperatures may be lower at the ground surface than at the tops of trees.
Physical spacing can be critical to plant survival. Closely spaced plants are continuous fuels and can conduct flames more readily and with a greater intensity than plants with greater distances between them. Chemical and physical characteristics of plants influence how they burn and their survival potential. Many evergreens are high in volatile oils and burn hotter and more quickly than deciduous plants. In summer, deciduous plants have a higher moisture content than evergreens. Plants that are more likely to survive a wildfire have an open, loose branching pattern with less total vegetation overall. They also accumulate less plant litter within or underneath them.
If your landscape plants were damaged in a fire, be sure to provide them with enough irrigation water to keep the soil moist. Protect the trunks and large limbs of trees from sunburn until the leaf or needle area regrows. Wrap them with a permeable substance such as tree wrap or light-colored cloth or cardboard, or paint trunks with water-based (not oil or petroleum-based) paint. Loosen the wrap every few months to prevent girdling.
In the end, it’s often “wait and see.” Be patient. Plants are often amazingly resilient.