Gardening: Know when to prune to keep trees and shrubs healthy

With the end of the fall season comes the question of when is the best time to prune trees and shrubs. It’s not always a simple answer. There are as many ways to prune as there are trees and shrubs.

Fruit trees

Fruit trees are best pruned in March when the worst of the winter cold has passed. Right now, the trees are relocating sugars and starches stored in the branches into the root system. That will take a few weeks to accomplish. Even when they are dormant, severe cold can damage branches and cutting them back too soon can open the tree to more cold damage. Pruning individual types of trees varies, too, so do some research before you prune.

If you want to learn how to prune and graft fruit trees, mark your calendars for March 31 and April 1. WSU Spokane County Extension will be bringing Gary Moulton to Spokane for a Friday evening lecture on pruning and then a full Saturday on hands-on practice of pruning and grafting. Before he retired, Moulton spent decades working with fruit trees at the WSU Mount Vernon Research Station.

To register for the Fruit Tree Pruning and Grafting class, go to the WSU Spokane County Extension website and check the calendar on the right-hand side of the page. http://extension.wsu.edu/spokane/.

Ornamental trees

Ornamental trees, for the most part, need little more than the removal of broken limbs or branches that are rubbing on each other. Doing more than this can destroy the shape of the tree and reduce its value in the landscape.

Conifers

Most conifers don’t need a lot of pruning. In fact, too much pruning destroys their shape and their function in the garden. Pruned conifers are often slow to regenerate branches in the cut area. Over time this may lead to dead areas that the tree can’t recover from. The only thing they might need is the removal of a few bottom limbs so you can maintain the area under them.

Very late fall and winter are the best time to move smaller conifers. Their fibrous root systems are easy to dig out. To move them easily, put them on a tarp and drag them to their new location, plant them at the same level they were originally and water them well. If you are in a windy area, stake them for the winter.

Shrubs

The proper time to prune a shrub depends on how it blooms. Shrubs like hydrangeas (the blue macrophylla), lilacs, spirea, Oregon grape and rhododendrons should be pruned right after they bloom. Their flowers are held on wood that grew the previous summer. If they are cut back over the winter, you will lose all the blooms. Again, do some research to find out the particulars about each of your shrubs before you get out the pruners.

Trimming shrubs into little round balls usually isn’t a good idea. Each shrub has its natural shape that if left to its own devices creates a beautiful looking plant. Whacking back shrubs without paying attention to their natural shape often results in rampant growth that in the long run makes more work for you. Do your research first.

Pat Munts is co-author, with Susan Mulvihill, of the “Northwest Gardener’s Handbook.” Munts can be reached at pat@inlandnwgardening.com.