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Time to Prune?
By Chuck Martin, Dow Gardens Horticulturist
An important aspect of plant care is the pruning of the plants. Plants are pruned for aesthetic appearance, the health of the plant, an increase in flowering or fruiting, and for safety reasons. In order to have healthy, fruitful, attractive plants, proper timing should be considered. There is an old adage that states, “Prune when the saw is sharp.” It is true that a sharp saw is good for the plant and also a preventive for sore muscles. The fact of the matter is that there are proper times of the year to consider extensive pruning for the best health of your plants.
The worst time of the year to prune is during the Stanley Cup Playoffs. If any woman even dares to ask their spouse to prune during these games, there is no telling what kind of creature the plant would be turned into. I can guarantee that things would quickly get ugly.
The time of the year to prune deciduous shrubs and trees is March and April or once the risk of severe chilly weather has passed. Removal of branches other times of the year won’t kill the plant but the best time of the year to prune is right before the end of the dormant period. Go ahead and cut out those branches that are dead, dieing, or about to poke out your eye. Cutting these branches will not harm the plant.
The timing of pruning the neighbor’s favorite flowering tree that hangs over the fence line, is up to your discretion and your relationship with the neighbors.
There is actually science supporting dormant season pruning. As a plant is coming out of dormancy, it is relying on its energy reserves with little photosynthesis taking place. There is still energy being taken from reserves until the leaf is fully expanded. Leaves don’t truly produce excess energy for reserves until late summer early fall. Leaves are like our children zapping energy and money from their parent reserves until that one day when we are in a nursing home in diapers and they are giving back to us.
Pruning plants with expanding leaves are already low in carbohydrates. So wounds will seal over at a slower pace. If you cut the branches before the expansion occurs fewer resources will have been taken from the plant and more can be used in growth to seal over the wounds.
Pruning during the dormant season has a practical side to it also. This is the time of the year you can see the branching structure and pattern with out the leaves. This allows you to see crossing and rubbing branches and better determine which branches must go.
During the dormant season of plants, insects and disease spore activity is low and less likely to infect the wounds. This is the reason why elms and oaks are pruned only in the dormant season. The risk of Dutch elm disease and oak wilt is too great to prune these two plant types during the growing season. Both these diseases can eventually kill the trees.
If you must prune oaks during the growing season you might consider painting the wounds with a latex paint to discourage the picnic beetles from visiting the wounds. Picnic beetles are considered vectors of the oak wilt disease.
Some plants such as birch, maples and walnuts “bleed” when pruned in the early spring-late winter. Squirrels have a blast breaking branches off these plants over your car and sidewalk in the spring. Although the oozing of the sweet sap might be annoying to the homeowner it doesn’t seem to harm the tree. In fact, some experts think that the oozing might actually prevent decaying organisms from colonizing. This was the exact thought of my mother when I came home with a cut. “No stitches for my kids.”
I hope this article will help you to decide whether or not to get out and prune or continue to procrastinate.
1809 eastman avenue • midland • michigan • 800.362.4874 • tierney@dowgardens.org
