Plant health and fire safety seem, at first glance, to have little in common. However, stressed evergreen trees (pines, spruce, etc.) often have dying or dead branches, twigs and needles. These are more likely to ignite and burn in a wildfire than green thriving branches and needles.
Keeping evergreen trees healthy is an important part of reducing a property’s wildfire risk. Proper pruning can help keep trees healthy.
During years of above-average winter and spring precipitation, evergreen trees thrive and need little care, including pruning. However, during dry years they may show significant signs of stress and need careful pruning to eliminate dead or dying parts.
Correct timing of pruning evergreens is imperative to prevent or reduce bark beetle attacks. Evergreens pruned in spring or summer, when sap is flowing, are more likely to be attacked by bark beetles.
The perfect time to prune pines, spruce, junipers, arborvitae and other evergreen trees begins after freezing temperatures occur in the fall and continues through the winter. This is a great time to sharpen your shears, loppers and saws and prune.
Start by removing dead, dying or damaged branches or limbs. Living branches may need to be removed to shape a tree or to eliminate a hazard such as a branch blocking wires, walkways or driveways.
The most important rule for pruning trees is to be sure not to cut or damage the branch bark collar or the branch bark ridge (see graphic). This is called a “flush cut.” Flush cuts damage or remove the branch collar. This prevents the tree from being able to compartmentalize or “heal” the pruning cut. If the cut can’t seal itself, insects and disease can attack the tree.
The best pruning cut is made just outside the branch collar, at a 45- to 60-degree angle to the branch bark ridge.
Whenever removing limbs greater than 1 inch in diameter, use the three-cut method to avoid tearing bark. First, about 12 inches from the trunk, cut halfway through the limb from the underside. Second, about 1 inch past the first cut, cut through the limb from the top side. The limb’s weight will cause it to break between the two cuts. Make the third cut just outside the branch collar to get rid of the remaining stub. Do not apply tree paint or wound dressing.
By taking good care of your evergreen trees, you will have beauty and shade and reduce the threat of ignition in a wildfire.
JoAnne Skelly is the Carson City/Storey County Extension educator for the University of Nevada Cooperative Extension.