Neil Sperry

Avoid these egregious errors when pruning your plants

A great garden in a small space

Jake and Sharyn Schaffer's patio garden in San Luis Obispo makes the most of the small landscaping space.
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Jake and Sharyn Schaffer's patio garden in San Luis Obispo makes the most of the small landscaping space.

My goal here usually is to focus on the positive – to pass over the mistakes gardeners make. However, when it comes to pruning, some of the errors are so egregious that they just can’t be swept under the carpetgrass. They seem to make no sense at all. Please let me point out a few.

Pruning just to be pruning

As hard as it is to imagine, there are people who just feel the need to be pruning their plants. Perhaps they think it makes the plants healthier, or maybe they feel it’s something you have to do as a rite of the season. Whatever the reason, they find themselves out in the yard, saw and shears at their sides.

Fact is, you need to have a real reason for pruning. My own somewhat educated guess is that probably 80 percent of the pruning I see being done wasn’t needed at all in the first place. Do your research, and if you can’t find justification for trimming your trees, shrubs and vines, don’t do it.

How much can I prune back my shrubs?

That’s a question I’m asked almost weekly. Unfortunately, it usually masks a much more serious problem – they have the wrong plant in the first place. If you have a plant that is constantly growing too tall or too wide for the space you have available for it, you need to do more than just trim it. That’s because its size is genetically predetermined and it’s just going to grow back.

If rare reshaping, as in every five or 10 years, isn’t enough to keep it in bounds, you either need to move it, or remove it entirely. There are plenty of high-quality plants that grow to any given size to take its place. Let your nursery professional guide you into making good choices.

Leaving stubs when they prune

Oh, this is so sad. Gardeners, even paid professional plant people, will take a limb off a tree and leave several inches of stub in place on the trunk. That’s a sure recipe for disaster years down the road. To heal properly, a tree’s trunk needs to be able to form new bark across a pruning wound.

Unlike human wounds where scabs quickly form, bark must grow in from the sides to heal tree wounds, and if there’s a stub sitting there, the new bark is blocked off. Decay will start in the stub. After several years the decay will have progressed down the stub and into the main trunk, then down the trunk until the tree is damaged or killed.

Pruning to eliminate the stub would have bypassed all of that trouble. Leave about 1/8-inch of the branch collar, that is, the swollen area where the branch intersects the tree’s trunk. Pruning paint is only recommended when oaks are involved. It greatly reduces the chances of the oak wilt fungus invading through the cut surfaces.

Pruning at the wrong season

You can always remove dead or damaged tissue from any plant at any time. However, most other pruning is best done at specific times. Mid-winter pruning includes fruit trees (especially peaches and plums) and grape vines, summer-flowering shrubs and vines, evergreen shrubs, and bush roses.

Spring pruning comes immediately after spring-flowering shrubs and vines complete their bloom cycles. You can also remove erratic new growth from your evergreen shrubs.

Blackberries are pruned immediately after you finish harvesting the berries. Remove all canes that just bore fruit. They will not bear fruit again. You can also remove dead and browning foliage from perennials as the plants cycle out of bloom.

Shearing into unnatural shapes

Okay. I’m setting myself up to get hate mail, but in reality I’m just trying to save you a lot of repetitive trimming. My own goal is to buy plants that grow to the size and form that I want, then to let them grow to those shapes without constant trimming. No boxes or globes unless I’m trying to create a very formal garden design.

Sure, I’ll trim off erratic branches that make a plant look unkempt, but I’ve always felt that rows of square shrubs across the fronts of our houses just repeats the manmade lines of the buildings. It does little to highlight the natural beauty of landscaping.

Failing to prune plants that need it

I can cite several examples. New trees and shrubs that have been dug with loss of roots in the process should be pruned to compensate for those losses.

Grape vines and peaches and plums are pruned every winter. Roots that encircle one another or the trunks of their trees should be pruned before they can do damaging “girdling.”

Topping crape myrtles

I waited as long as I could. This is simply a horrible practice that has absolutely no justification. There are those who say they have to do it because their crape myrtle plants get too large, but we’ve already refuted that comment – the plants are just going to grow back.

Some feel that it makes their crape myrtles bloom better, but research has shown that it does not. Topping causes plants to bloom six or eight weeks later and to bloom only one time per summer instead of two or three, perhaps even four. Plus, since crape myrtles are bare for five months each winter, you have to look at the ugly stubs almost half of the year.

Don’t top crape myrtles. Or, if you have one that has been topped, cut it to the ground and let it regrow. You’ll have a full and beautiful crape myrtle within just a couple of years. Try it – it works!

You can hear Neil Sperry on KLIF 570AM on Saturday afternoons 1-3 pm and on WBAP 820AM Sunday mornings 8-10 am. Join him at and follow him on Facebook.