It's pruning time again for many trees and shrubs. Surprised? Most people tend to believe that pruning is exclusively a winter or dormant season chore and they end up confused or frustrated about why their plants have very few blooms. Pruning at the correct time will help produce magnificent floral displays or an impressive crop of fruit.
The best time to prune your trees and shrubs is determined by a number of factors:
- bloom time
- whether they bloom on new or old wood
- how vigorous their growth is
- if they are heavy bleeders
- whether they have diseases that are easily spread during rainy, winter weather.
Certified arborist Philip Frazee, owner of Arbor West Tree Experts in Eagle Point, says the most important thing is to leave the branch collar intact. Don't make the mistake of removing too much inside growth of the trees. When temperatures reach 90 degrees, the exterior foliage of the tree shuts down. Shaded by the outside canopy, the cooler inner foliage sustains the tree.
Another reason not to prune out too many interior branches is that they aid in the build up of the diameter and strength of the scaffold limbs, says Willie Gingg, manager of Southern Oregon Tree Care in Medford. Lion tailing, or stripping out the foliage on the branches, leaves trees top heavy and more prone to wind damage and cracking in the summer. Gingg also recommends against pruning conifers from May through September as the oozing sap from wounds may attract the bark beetles that can kill them.
Trees such as birch, dogwoods, maples and walnuts are known to be heavy bleeders when they are cut in late winter or early spring. Although the bleeding looks alarming, this usually doesn't damage the tree. It is good, however, to prune these varieties in the summer as the dripping sap could damage the bark in some cases and can be dangerous if the dripping gets onto sidewalks.
If you own a fruit tree with multiple varieties grafted on it, the varying growth rates of each type may have resulted in a lopsided tree. An initial late winter pruning plus supplemental summer pruning on the more vigorous limbs will keep the tree balanced. A little summer pruning on fruit trees can also aid in the production of fruit spurs when you cut back several inches on some of the longer branches.
A long list of spring-blooming, ornamental shrubs should be pruned soon after they have finished flowering. This includes Deutzia, dogwood, lilac, forsythia, mock orange, spirea and holly. If they are pruned too late, you may cut off all or many of the flower buds that have formed for next year's bloom. July 4 is a good date limit for pruning most of them. Rhododendrons and azaleas should be pruned before the new growth buds swell, which is soon after flowering. Remember to remove any seed head formations as this uses up energy that could be put into forming new flower buds for next year.
Many rose varieties need to be repeatedly pruned during the summer months to promote continual flowering. When you allow rose hips to form on your shrubs, it's a signal to the bush to stop producing flowers and to set seeds.
Hopefully, you're inspired to research your trees and shrubs to learn their growth patterns and pruning needs before you get out the loppers. Check with your nursery or Master Gardeners (776-7371) for more information about correct pruning times for various plants.