I don’t think any topic causes more fear and trembling among gardeners than the subject of shrub pruning. Because they fear making an “unkindest cut” at the wrong time or in the wrong place, gardeners often leave the shrub untouched until it grows into a scraggly mess that can’t be recovered.
Yes, it’s true that you can harm a shrub by pruning too severely, though it’s not likely. And it’s also true that you can eliminate a season of flowering by cutting back at the wrong time. But shrubs need pruning as much as they need sun and water. Unpruned shrubs eventually grow too dense and become prone to disease. Unpruned shrubs will, over time, flower or fruit less frequently. Shrubs, especially those grown near a home’s foundation, often get out of control and cover windows—even doorways—and need heading back. So pruning shrubs is one of those chores you shouldn’t ignore. Let’s gird ourselves, hold hands and get through this together.
First up, pruning tools. All you need are hand tools. If you require a chainsaw or something larger, you’ve waited too long to prune. You’re killing, not pruning. First, get yourself a good pair of hand pruners. I prefer bypass pruners, which work like a scissors, to the anvil type. Felco brand hand pruners are among the best. For branches of a half-inch thickness or more, get a pair of lopping shears. Many manufacturers make good ones; just check to make sure the business end is sharp and heavy-duty. If you’re cutting branches of more than an inch in diameter, you ought to have a pruning saw. These are made to cut on the pull rather than the push. A good one will cut cleanly and quickly.
When, what and where?
So now let’s talk about what to prune, where on the plant to prune and when to prune.
“When” is probably the least understood, especially when it comes to flowering shrubs. Prune at the wrong time and you can eliminate a season of flowers. So remember the rule of June 1: If the shrub flowers before June 1, prune immediately after flowering and no later than the end of June. If it flowers after June 1, the shrub is best pruned while dormant, the month of March being a perfect time. (See the sidebar above for common shrubs that bloom before June 1 and after June 1.) March also is a good time to prune evergreen shrubs, though they also can be lightly pruned in early summer.
As for “what” to prune from the shrub, you’re going to cut out anything that is dead or diseased. (One advantage of pruning during the dormant season is you’re unlikely to spread disease as you’re cutting into branches.) Then look at the branches and eliminate any that are rubbing or crossing one another. Suckers are weak growth that usually stand at a sharp upward angle to the rest of the plant; those also should be taken out. Finally, look at the base of the shrub. If the branches are so dense you can barely see through them, it’s time to take out the older ones (they will be larger) and make more room. Use a thinning cut, described below, and take them down to the ground.
Now on to “where” to prune. It’s a little more complicated than “when” and “what.” If we want to direct the growth of the plant, shorten it, or make the shrub “bushier,” then we’re doing what’s called a heading cut. A heading cut is done toward the ends of the branches and stems. Heading cuts should be made back to a good bud or lateral branch, preferably one that is growing out away from the center of the plant. Do not leave short branches—or stubs—on the shrub after a heading cut.
Before making heading cuts, stand back and visualize the shape you want the shrub to maintain and make the cuts that keep it in those bounds. In most situations, you want to cut down no more than a third of the shrub at any one time. However, some summer-blooming shrubs—like butterfly bush, vitex and crape myrtle—actually thrive on being cut all the way to the ground.
The second kind of cut is called a thinning cut. Thinning cuts remove all of the branch back to a main branch or trunk. Thinning cuts open up a shrub, allowing better air flow and sunlight penetration, which makes for better flowering and/or fruiting. On a mature deciduous shrub that is not outgrowing its space, you’re going to use more thinning cuts than heading cuts. On an evergreen, you’re going to use more heading cuts to keep it growing full and bushy or to shape it into some pattern.
The good news is that shrubs, properly pruned, can go for at least two years, maybe as many as five, before they need another haircut.
Spare the Flowers
Pruning flowering shrubs at the wrong time can eliminate a season’s bloom. These shrubs should be pruned just after the blossoms fade and no later than the end of June:
- Amelanchier (serviceberry)
- Berberis (barberry)
- Calycanthus (sweet shrub)
- Flowering almond, cherry or plum
These shrubs can be pruned when the plant is dormant, late February through March:
- Althea (Rose of Sharon)
- Butterfly bush
- Clethra (Sweet pepper bush)
- Roses (garden bush varieties)