Pruning is a mix of art, science

As we edge closer and closer to spring (wishful thinking?), it is time to start thinking about pruning up a few of the trees and shrubs in your yard.

Pruning is necessary to keep your plants healthy, growing strong and producing flowers and fruits in abundance. And it requires proper technique and correct timing.

The timing of pruning depends upon when the tree or shrub blooms. If it blooms before midsummer (say, June 15 or sooner), it should be pruned after it blooms. If it blooms after midsummer, it should usually be pruned early.

The big exception is fruit — those trees and shrubs bloom early, but they should be pruned before dormancy breaks in late winter. Trees and shrubs that aren’t grown for their blooms that need pruning (and not all of them do) can be pruned at any time, but dormant pruning in late winter would be preferable.

If you are unsure when to prune, take a look at the type of wood on which the flower buds form. Early bloomers tend to bloom on wood grown in the previous year, so in those plants you should prune after blooming (except, once again, fruit). If the flower buds form on new growth from the current year, then pruning early is desired.

You’ll especially need to take note of some plants that vary depending on type or variety. Roses are a good example. Some roses, such as hybrid tea, floribunda, grandiflora and modern everblooming types, bloom on new growth and should be pruned in late winter. Ramblers and climbers, along with lots of others, either bloom on old wood or rebloom and should be pruned after blooming.

The way to tell the difference between old and new growth is usually pretty simple. Older wood typically has a rough bark and is thicker than new growth. New growth usually has a slick, easily peeled bark that is usually a brighter color than old growth.

The science of pruning

There are several things that pruning does for your trees and shrubs. In plants, the set of buds at the end of a branch or the top of a tree release a hormone called auxin that keeps the rest of the buds along the branch from growing. This phenomenon is called apical dominance. Once you remove that terminal (apical) bud, the rest of the buds along the plant will grow out and allow the plant to bush out.

Pruning also improves the airflow throughout the plant, which can aid in reducing instances of disease. It helps leaves stay drier, which reduces how much fungal diseases can grow.

In fruits, pruning also helps improve fruit quality. Opening up the canopy allows more sunlight to hit the leaves, which results in bigger and sweeter fruits. Reducing the number of flowers (and therefore fruits) also results in larger fruit.

Those who grow certain flowers, like roses, also find that pruning out the number of flower buds results in bigger, showier flowers — a must for those who like to enter flowers into competitions.

Pruning basics

Part art and part science, pruning requires some basic skill and know-how to get done properly. We’ll talk about a few of the basics to get you started.

First, when you are removing that apical bud, called heading back, you want to cut back to either a branch or bud that is growing in the direction you want the branch to go. You don’t want branches growing too horizontally or vertically; the connection to the tree is weak and prone to breaking. It also affects the flowering and fruiting on that branch — straight vertical growth is mostly leafy and horizontal is mostly floral. For both strength and balance, you usually want the branches on your fruit trees to be at about a 45- to 60-degree angle.

Next, you want to make sure that you don’t leave a long stub when you prune. Leave only about a quarter-inch from the cut to the branch or bud. If you are totally removing a branch, the swelling at the base, called the collar, is your guide.

If you are pruning certain shrubs or bramble-like fruit, such as raspberries and blackberries, you need to remove whole canes all the way to the ground (some heading back on big growers like blackberries is OK). After brambles bloom and fruit, the cane dies back and should be removed. There are some newer varieties (called primocane varieties) that bloom both in the fall and spring. The main crop is in the fall. You can either wait until after the smaller spring crop to prune, or cut the whole thing down in the fall if you aren’t worried about the crop.

This method of pruning is also best for ornamental shrubs that have a fountainlike growth habit. The one that comes to mind to me is forsythia, that yellow shrub that blooms early in the spring. It is a major pet peeve of mine to see them shaped up like a hedge. It severely reduces flowering and just looks unattractive. If you cannot let the plant grow to its full potential, perhaps it needs to grow elsewhere — but that is just my little peeve.


2 thoughts on “Pruning is a mix of art, science

  1. Dear Mr.Porter:
    I have two miniature citrus plants which look like “baby trees” Should I prune now; or, should I wait until Fall?

    Would you send me an illustrated copy of what to do and how to do it? THANKS!!

    Nick Winowich

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