It may seem odd to see Pittsburgh Parks Conservancy staff and City DPW crews out in the bitter wind of January, but the winter months are actually the ideal time to give your trees a little attention. In fact, winter pruning ties into our Tree Action Plan as an effective way we can manage the current threats to our urban forest. “In winter the fresh cuts have time to dry out,” says Angela Masters, Parks Conservancy horticulturalist. “When the insects and diseases become active in spring the wood isn’t susceptible to colonization.”
Pruning young trees on your property is beneficial in a variety of ways. Proper pruning helps the tree send its resources to the good strong branches, so that it grows stronger and is less of a liability during a storm or bearing the weight of heavy snow. In addition, “A well maintained tree will serve the community best through storm water management, carbon capture, erosion control, and shade,” says Parks Conservancy Field Ecologist Bryan Dolney.
Before you pick up the limb loppers, make sure the timing is right. A homeowner should feel comfortable doing developmental pruning, which means that the tree is more than one year old, no more than 20 feet in height, and 3-5 inches in diameter. “Don’t prune your tree in the year immediately following its planting,” advises Phil Gruszka, certified Arborist, and Parks Maintenance and Management Director for the Parks Conservancy,” unless it has one of the four D’s.” Limbs that are dead, dying, diseased, or damaged. This first year is when the tree’s root system is reestablishing itself and unnecessary pruning will disrupt its growth. Equally important is not attempting to prune a tree that is too large because it can become dangerous and should be left to professionals.
While it may be tempting to prune your tree into a pretty sphere, the primary purpose of pruning should be done with the tree’s structure as the paramount concern. Angela also warns to resist the impulse to “limb the tree up,” or cut away at lower branches while neglecting the higher ones. “Try not to remove more than 25 percent of the tree’s live branches while pruning,” she adds. When you’re decided which limbs will stay and which will go, keep your eye out for these primary issues…
Codominant stems. Codominance is when two or more stems are competing to become the dominant leader. Codominant stems grow parallel from one another and form a ‘U’ or ‘V’ shaped crotch.
‘U’ shaped crotches are strong, there are wood cells growing in the bottom of the ‘U’ which connect the limb to the trunk, keep these whenever possible.
‘V’ shaped crotches are not strong because there are no wood cells growing at the point of attachment. ‘V’ type crotches frequently capture outer bark as the tree grows. This bark, called an “included crotch” becomes included in the growth, preventing wood cells from connecting the limb to the trunk. If a tree continues to grow in this manner it will eventually split, potentially causing serious damage on your property.
Rubbing branches. Think of the way a bow rubs against the strings of a violin. Like water to a stone, the branches rubbing against each other over time will cause damage and eventually, fallen limbs.
Dead branches. It’s pretty simple, dead branches can fall causing damage to both your property and other branches. They can also potentially be diseased and damage the health of your tree.
Deformed branches. If it doesn’t look right, it probably isn’t.
Suckers. Also called water sprouts, suckers are small limbs that grow vertically in patches either off of a branch or out of the ground surrounding the base of a tree. They are aptly named as their primary dysfunction is that they suck resources away from larger, more vital limbs on the tree. Suckers on your tree are an indication of poor health (often because of improper depth when planted) so you should consider having an arborist take a look at it.
Now that you know what to prune, how to prune it? “Cut a branch where there is a new shoot or a new branch coming out,” advises Angela. A tree is not a bush, instead of hedging the whole outside of the tree, make decisive reducing cuts to the branches. In the case of a codominant or V shaped stem, select the healthier looking branch to become the new dominant stem and cut the other as close to the point of the V shape as possible.
Ultimately proper care of trees on your property is a benefit to both yourself and the community. Proper pruning at the right time will help slow the spread of disease and insects in Pittsburgh’s urban forest where we currently stand to lose more than 60% of our urban tree population to threats like the Emerald Ash Borer and Oak Wilt disease. Healthy trees also ensure that we receive their maximum benefit to the environment. Finally, taking care of your trees in the first three years of their life will save you expense resulting from property damage and arborist expenses for years to come.