One of the most frequent types of questions local nurseries receive is a pruning question. When? How? Why?
It is tempting to prune woody shrubs and trees right after leaves fall, when they reveal problems correctable by pruning, but dont be tempted. Colder weather is coming, and freeze damage might exceed what you consider disposable parts of a tree or shrub. Pruning Buddleias or butterfly bushes in fall, for example, has even resulted in their deaths in the Valley in recent years.
Pruning rose shrubs might provide wounds open to infection by bacterial cane disease that can result in the shrubs death. In our area, we recommend only fall pruning long rose canes that can whip in the wind, damaging other parts of the shrub. Other than that, leave the shrub alone unless youre harvesting rose hips for jelly, for instance.
Do you prune hydrangeas? Do not prune them. None of the types require annual pruning. Bigleaf hydrangea (also called mophead or lacecap) oak leaf and climbing hydrangeas all bloom on old wood. Old wood is that which has formed over the past year; you dont have to keep track of age.
The smooth or Annabelle hydrangea and the panicle hydrangea (also called peegee) flower on new wood, so may be pruned (if necessary for shape) in spring and still flower that summer. Just carefully remove traces of old blossoms from hydrangeas in spring so theyll look their best.
I prefer to do major dormant pruning of trees in mid- to late February, when we should be past the threat of severely cold weather. Thats also when you should prune grape vines.
The reasons we prune are for appearance and health of the plant, shrub or tree, and increased blooming (and/or fruiting). For grapes we prune to limit fruiting so the vine can supply fruit with optimum sugar.
For ornamental and food-producing trees and shrubs, pruning fundamentals are the same. The phenomenon known as apical dominance means the extreme tips of growth the top and the branch ends contain growth hormones that can be redirected by pruning. That is, nipping off the top or the ends of the branches sends those growth hormones lower (or toward the trunk), awakening and activating lower buds on the trunk or branch.
When these previously inactive buds break and grow, the shrub or plant becomes bushier, with more twigs and branches on which to set flowers, fruit or, in the case of basil, leaves. The more you prune, the more compact and bushy a plant becomes.
We also prune to improve the appearance of woody plants. A vase-shaped tree, for instance, is not attractive when one branch or another outgrows all of its neighbors.
Yet we want to get air circulation and sunlight into the plant to avoid problems with mildew or other moisture-retentive diseases.
Eliot Coleman and his wife, Barbara Damrosch, have authored an article in the Dec.-Jan. 2014 Mother Earth News on growing greens year-round in a cold climate. They do that in Maine, a much colder climate than ours.
They advocate using a low-cost movable greenhouse to protect plants during cold weather. Three things should be emphasized for this project: Time planting so that crops are harvestable by the time we have less than 10 hours daylight; move the greenhouse (and row cover, if using for secondary cover) into place over crops while soil is still warm from the summer; and firmly anchor the greenhouse from blowing away.
The portable greenhouse they advocate weighs about 100 pounds. I had a small, lightweight greenhouse erected in what I thought was a sheltered place until it hopped over my house and landed in the front yard.
Send garden questions to firstname.lastname@example.org or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.