Mighty oak still needs tender care at pruning time
Q. Is this a good time to prune our oak trees? My spouse wants me to do it now, but I'd rather wait until the spring.
A. There are two axioms to consider here. The first is the one that says the best time to prune a tree is when the saw is sharp. The second is your spouse is always right. Always.
Regarding the first axiom, this is not necessarily so. Some trees may suffer if pruned at an inappropriate time. Oaks, especially, when pruned during active growth, run the risk of sap escaping from the cutting site and the scent of fresh cut wood attracting oak borers, which are carriers of oak wilt disease that can be fatal to any of the nearly two dozen species of oak native to Illinois.
Oak wilt is a fungus that travels on oak borer beetles and consequently can enter an oak at the site of open sap. If you must prune an oak during active growth, use wound dressing, or latex paint to mask the scent of the sap to avoid attracting insects that harbor oak wilt spores.
A further advantage of dormant season pruning is that you are able to see the true "bones" of the tree and prune out damaged or dead limbs, and limbs that are rubbing against each other, while maintaining the aesthetics of the tree's symmetry.
Native doesn't mean problem free. An oak weakened by soil compaction, storm damage, or harmful chemicals such as road salt will be more susceptible to further weakening by insect damage. Although the white oak, the State Tree of Illinois may seem like a strong giant, growing to 80 feet and living centuries, suburban life with its chemicals and subdivisions places stress on these magnificent trees. The drought we experienced in 2012 may still affect many trees today.
Take care of your oaks, and take care of yourself by using the proper pruning equipment, whether it be lopping shears, hand saw or chain-saw, and wearing safety gear.
- Matt Steichmann
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.