To Prune or Not to Prune?

By Melanie Mathieson
Gardening Guru

As gardening season fast approaches many gardeners feel the urge to get out in the yard and start pruning their trees and shrubs. Keep those pruners under lock and key because spring is not the time of year to prune most trees and shrubs.
Pruning your trees and shrubs at the wrong time of year can cause more damage than you may realize. Tree species such as maples and birches have a very liquid sap that starts to flow through the tree as the weather warms up in the spring. Pruning birches and maples as the sap is running freely through the trees will cause bleeding of the sap, out through the wounds, you created. The loss of sap is very stressful to the tree, as sap is the food for the tree and removal may cause the tree great harm or even death. If you prune flowering shrubs you may be removing the areas with the flower buds from the tree and then the tree will not flower this year. Lilacs and snowball trees have their flower buds for next year at the bases of this year’s flowers so by pruning off the ends of the branches you will remove the flowers for next year. The general rule of thumb for pruning most tree and shrub species is to prune in June. This allows time for the sap to stop flowing freely, the flowers to bloom and this year’s new growth to emerge. Evergreen trees should be pruned at this time of year, so as to allow time for new buds to form over the summer for next year’s growth. June is also a great time to reshape your hedge whether it is an evergreen or deciduous hedge.
Spring is the appropriate time of year to prune those shrubs that need to be cut back to the ground, in order to produce for this year, such as Annabelle hydrangea and butterfly bush. There are only a few other shrub species that require this type of severe spring pruning, so consult your nursery if you are not sure about your species of shrubs. You can remove the dead growth on roses with spring pruning. Prune only the dead grey wood away not the green wood. Spring is also a great time to prune out last year’s raspberry canes from the raspberry patch. Last years canes are dead and will not produce fruit again. Other than that there isn’t much else that you should be pruning. Save your cosmetic pruning and grooming for June as stated above. Now if you have trees with damage from the winter or areas with disease, you may prune the areas of damage from the trees in spring. This applies to all trees and shrubs, with the exception of maples and birches as you should wait until June, as mentioned above.
Pruning can be used for the cosmetic shaping of trees and shrubs and was performed regularly on the tree and shrub species of yesteryear. We have talked about hybrid plants and vegetables in past columns but you may not realize that most of the trees and shrubs available at our nurseries today, are hybrids of past varieties, that require much less care and need little to no pruning in order to maintain their form. Many of the new varieties are called compact, which will grow within a smaller size range, globular, which remain in a ball shape, pyramidal, which will remain in a triangular form and columnar, which grow in a cylindrical shape, all of which retain their form and shape without regular pruning maintenance. If you have any of these new hybridized forms and species in your yard you should never need to prune them for shape. Pruning should only take place if you have damaged or diseased branches.

Not only is timing critical for pruning but so is technique and proper removal of the branch. Ensure is that your pruning tools are very sharp. You want to remove the branch with minimum damage to the tree and sharp tools ensure a good clean cut. Branches to be pruned must be cut back to an intersection of the branches, where the tree forms a “V-shape” at the intersection. When removing damaged or diseased branches find this “V” intersection in the healthy wood. If you are pruning for reshaping, find this “V” intersection in an area of the tree that provides the desired shaping. To remove the undesired branch, prune off the one side of the “V” flush to the remaining healthy branch, using great care, not to cause any damage to the healthy bark or branch with the saw or pruning shears. Trees have the ability to seal over wounds, over time, if cut is clean and flush. Under no circumstances should you leave a branch stub. The tree cannot heal over the end of a branch stub and this leaves the tree open to future insect and disease damage. So make sure you have a nice clean and flush cut, so the tree can seal over the wound. Because a tree can repair itself if you do the pruning properly you should never apply paint or sealant to the fresh cut. Paint and commercial tree wound sealing products prevent the tree from naturally sealing over the wound. Depending on the size of the branch removed, it takes a few years for the tree to form a complete callous seal over the wound, making the wound almost undetectable.
While doing your spring garden cleanup, make sure you trim away the small sprouts at the base of your trees and shrubs. I do not consider the removal of these actual pruning, but it is a necessary step to ensure good tree health and vigour and these can be removed any time of the year. Those small sprouts are called stump suckers and will never fully develop into sound and solid wood and also rob energy from the main tree, so by removing them you direct the food back into the main stem of the tree. Some tree and shrubs are more susceptible to developing stump suckers so keep an eye out throughout the season and remove them as soon as you see them developing, by cutting them flush to the base of the trunk and as close to ground level as you can get.
To prune or not to prune, was your question and this column has provided you with the answers of when and how to prune. Proper pruning will ensure the health and vigour of your trees and shrubs for many years to come. Sharp tools, proper technique and the right time of year will guarantee your success. So keep those pruners under lock and key until they are absolutely needed, allowing you focus on the other, more necessary, yard and garden duties.