When should you cut back trees and shrubs?
One of the most common questions arborists are asked is when should you cut back trees and shrubs? This article will discuss some of the most common trees that grow in our neighbourhoods and the best time to prune them.
What trees and shrubs grow in Toronto and the GTA?
Our part of Ontario is blessed with a multitude of trees and shrubs that thrive in our continental climate. In Toronto alone, we have millions of trees both City owned and privately owned. We are home to some magnificent specimens of heritage trees and are recognised internationally for our urban forests. Whitby, Vaughan, York Region and Toronto have all been awarded International Tree City status.
Black, bur and white oaks, silver, sugar and black maples, black walnut, trembling aspens, black cherry, white cedar, yellow birch, American or blue beeches, white pine, green ash and hemlock are just some of the native species that are commonly found here. As native species they are perfectly suited to our soil conditions and climate so are more likely to thrive here. But to keep your trees healthy they still need regular maintenance. Pruning your trees is an essential aspect of tree care and needs to be done every year. If you want a decent crop from your fruit trees you will need to prune them so the tree’s energy is harnessed for fruit production.
Why do you need to prune trees?
Apart from cutting back trees to improve their shape and appearance, tree pruning is essential for the health of your tree. Pruning out dead, decaying or broken wood prevents disease or decay taking root. It will also mean that the tree is less vulnerable to storm damage in extreme weather. Tree trimming promotes growth and encourages flower and fruit production. Finally, thinning out the canopy lets light and air circulate, meaning healthier growth.
When should you cut back trees and shrubs? The best time to prune trees in Toronto and the GTA.
If you prune trees according to proper arboricultural guidelines, for example, minimizing the size of the wound, it is actually possible to prune trees at any time of year. However, there are two times of year when it is generally better for you to carry out a more thorough tree pruning – winter or early spring. In addition, some specific species of tree are best pruned at particular times of year. The extent of pruning that the tree needs will vary between species. Some, like Dogwood, rarely need vigorous pruning, but others, such as planes or poplars can tolerate a more thorough cut back.
Another factor to consider is the maturity of the tree. With a mature tree, the basic structure of the tree has already formed and the roots are well established. But with younger trees the way in which you prune them in their early years can have serious consequences for both their rate of growth and the eventual shape and structure of the tree.
The final factor to consider is whether flowering trees flower on old or new growth. Most trees or shrubs that flower in early spring, such as lilacs, forsythia and magnolia produce buds on old wood. These should be pruned immediately after they have finished flowering. Do not trim trees or shrubs that flower on old wood in the Fall if you want to have flowers the following Spring!
When should you cut back deciduous trees?
Deciduous trees such as oak or ash can be pruned once the tree has entered dormancy, that is, when they are not actively growing. So through late Fall and early Winter. There are a number of advantages to pruning at this time of year. Once the leaves have dropped it is easier to see the structure of the branches. In addition, most insects are no longer active at this time of year so there is less risk of the open wounds becoming infected and it will give the wounds time to heal before they become active again.
Due to the threat of Oak Wilt in Ontario, it is particularly important that you do not trim your oak trees during the growing season. You can find out more about the threat of Oak Wilt in our separate article about Oak Wilt.
Be careful not to prune your trees too early or you may stimulate regrowth. If you choose to prune your trees later in winter, you run the risk of possible damage from frost. Birch, cherry and maple are all trees and shrubs that should be cut back in the Fall if you are going to trim them. Avoid pruning these trees late in the summer.
When should you cut back fruit trees and flowering trees?
Pruning of fruiting and flowering trees is essential for a good level of fruit and flower production the following year. If you allow too many flowers to develop, means energy that could be put into fruit production is exhausted and so less fruit will be produced.
Another reason for pruning fruit trees is to open up the tree so that the fruit that are produced get sufficient light to develop well. Again, pruning needs to be done when the tree is not actively growing, so winter is ideal for many species. If pruning in the winter, be careful not to prune too early or too late. A good rule of thumb is to prune between December and mid February, before buds start to be produced. Deciduous fruit trees such as apples, pears, peaches and plums will all benefit from being pruned in mid Winter.
When should you cut back evergreen trees?
Many evergreens do not require much pruning at all and trimming is principally done for cosmetic reasons – to maintain the shape that you want. Broadleaf evergreen trees should be pruned in early Spring just before their annual growth spurt. Needle leaf evergreens like juniper, fir, Douglas fir and yew should be pruned early in the growing season. Avoid pruning evergreen trees in the Autumn as this will weaken them before the coming Winter.
