Why do we bother to prune trees and shrubs? It may seem like just another chore that has to be done but it can make a huge difference to the look and shape of your garden.
We prune to remove dead, damaged and diseased branches. Pruning out old, thin and weak wood helps trees and shrubs to stay healthy and vigorous. It is important to have good air circulation in shrubs and to get rid of damaged branches, which may permit disease or insects to take hold.
However there are also aesthetic reasons. Pruning can control the height and width of trees and shrubs. For instance I have some Amelanchier canadensis (serviceberries) and a Coral Bark Willow. Both of these will grow into trees if left to their own devices. By pruning them hard every 2 to 3 years, I keep them to a much more manageable size and shape. The pruning also encourages the willow to send up an abundance of new, brilliantly coloured shoots. Pruning will stimulate flower and fruit development as well as colourful twigs. It is essential to cut back most dogwoods every 1 to 2 years to encourage new, brightly coloured growth. Without pruning, the old wood will gradually become brown and lose the marvelous colour that looks so great against the snow at this time of year. If you inherit a garden with old, overgrown flowering shrubs they can be rejuvenated by pruning back hard.
Evergreens can be kept compact and within their allotted space. Anyone who has tried to trim an overgrown cedar hedge knows how difficult this can be.
Pruning is done to keep trees and shrubs in a pleasing shape. Form, growth and flowering habit should be studied carefully so that the natural shape is not spoiled.
Trees are sometimes pruned to increase their structural strength. Most young trees need to maintain a single, dominant leader. Double leaders can lead to structural weakness and it is therefore best to remove one of them while young. It is a lot easier to prune young trees appropriately so that they will require little corrective pruning as they mature. However, poor pruning can cause damage that lasts the lifetime of the tree.
In order to be able to prune effectively you do need the right equipment. All your tools must be sharp so you should get them sharpened regularly or do it yourself. Poor tools results in torn, ragged cuts that make shrubs and trees vulnerable to disease and insect attack. The following tools are useful: bypass blade secateurs, lopping shears, and a pruning saw. Use the secateurs for small branches up to 1/2 “ in diameter. For anything larger us the lopping shears or pruning saw. Hedge clippers should only be used for hedges! In order to prevent disease spreading form one shrub to another it is a good idea to clean your tools with a 10% bleach/water solution in between uses.
Late winter, when the plant is dormant, is a great time to prune many trees and shrubs. It is easier to see the shape and any crossing, broken or diseased branches when there are no leaves. Fruit trees are always pruned prior to bloom. Late flowering shrubs such as potentillas, flower on the current seasons growth and therefore should be pruned in early spring prior to active growth. Spring or early summer flowering trees and shrubs such as forsythia are pruned after they have bloomed. Most evergreens can be lightly trimmed in early spring if this is necessary to maintain their size and shape. Pines can have ½” of the new candles removed in June. Maple and birch trees will “bleed” if pruned in the spring so you may want to wait until mid summer.
First, remove all dead, damaged and diseased branches. This can be done at anytime of the year. Next look to see if there are any crossing or rubbing branches and remove the weakest. Cut out any weak, spindly branches and sucker growth. Remove older growth to soil level. When you have finished you should be able to see through the shrub, which will allow air to circulate freely. Stand back and look at the shape, shorten other branches to make a pleasing shape and size suitable for the space. Most shrubs should not have more than 1/3 of the branches in one year. However if a shrub is very overgrown and old you can cut everything to ground level. Pines and spruces will not grow back where you cut while forsythias and viburnums respond well to this treatment but will not flower for a couple of years.
Make cuts at a 45degree angle, ¼” above an outward facing branch or bud. Make sure that the bud is growing in the direction you want the new growth to take.
Hybrid tea roses are pruned in spring prior to leafing out by first removing any winter killed stems to an outward facing bud. Completely remove any dead stems to soil level. Remove any wood older than 3 years and create a balanced look. Shrub roses and ramblers flower on the previous years wood and can be pruned lightly after flowering. Explorer roses require little pruning, just cut out any damaged stems.
It is the right time to start thinking about getting you garden ready for the coming season and pruning is a great place to start. Master Gardeners will be available to answer any questions at the upcoming Peterborough Garden Show on April 11, 12 and 13 at the Evinrude Centre.