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CHAPTER 1

PART ONE Pruning Techniques and Tools

Once you understand the basic principles of pruning — why plants react as they do to pruning and how to make proper pruning cuts — you are well on your way to being able to prune any plant, even if you are not sure of its identity. You will also be able to tell when pruning is not needed.

The basics of good pruning are the same whether you are attending to a tree, a shrub, or any other woody plant. Although the sizes, angles, and appearance of stems and branches vary, proper pruning cuts remain the same. The best first steps are the same as well: Identify and remove dead, diseased, and damaged wood. Next, eliminate rubbing and crossing branches. The key is to learn to effectively use the techniques presented here to foster a healthy plant with sound structure and an attractive shape.

Pruning and Plant Growth

Pruning is much more than cutting off a dead or broken tree limb or chopping back a foundation plant. Every pruning cut affects the future health, growth, and shape of the plant. Do not let this statement scare you away from tackling this essential task altogether. Instead, use it to inspire a sense of serious purpose when you pick up a pair of shears or a saw. Taking the time to prune promptly and properly helps a plant stay healthy and vigorous. Making random cuts at the wrong time of year or in the wrong place can ruin a plant's shape, eliminate this year's flowers or fruit, or cause wayward growth to shoot off in all the wrong directions.

Poor or misguided pruning also can create a plant that requires constant pruning attention. Despite the fact that a great many gardeners prune to make plants smaller, pruning actually promotes growth. In general, hard pruning encourages growth; in other words, the more severely you prune a plant, the more vigorously the plant responds with new growth. While intensively managed plants — fruit trees are one example — do end up smaller than their unmanaged relatives, this is the result of repeated pruning sessions. Badly pruned plants generally respond by producing excessive amounts of vegetative growth, making them larger than their unpruned counterparts. Excessive vegetative growth also means fewer or no flowers and often an unattractive and unruly shape.

Understanding the basic biology that underlies plant responses to pruning will help you make good pruning choices.

How Wounds "Heal"

"Healing" is not really the correct word to describe the process that helps a tree recover from a pruning wound or damage caused by Mother Nature. Tree wounds never heal. Evidence of every wound, infection, and injury remains written in the wood of a tree throughout its life. Instead, damaged tissue is compartmentalized or sealed off to prevent disease agents from having access to the rest of the plant. As gardeners, it is our job to make the compartmentalization process as easy and as quick as possible. To help trees and shrubs compartmentalize wounds quickly, we need to take the following steps:

Cut off branches at the main trunk or where the branch joins another branch. These are called thinning cuts. Always make clean cuts, and do not damage the branch collar or leave living or dead stubs attached to the plant. (See Thinning Cuts Step by Step and Thinning Cut Mistakes for directions on making proper thinning cuts.)

To encourage branching, make cuts just above a bud or pair of buds. These are called heading cuts. Do not leave a stub above the bud, as this will provide access for disease agents. (See Heading Cuts for directions on making proper heading cuts.)

Prune at the proper time of year. See the plant lists in part 2 for timing.

Train trees when they are still young. This establishes good structure and prevents the need to make large pruning wounds later in the tree's life. Small wounds "heal" faster than large wounds, and wounds in young plants and young wood "heal" faster than they do in old wood.

Do not overprune. On healthy trees, remove 25 percent or less of the tree's canopy per year. Prune unhealthy or declining trees even less — pruning is stressful. Topping and other pruning methods that remove more than 25 percent of a tree's canopy damage the tree and cause decline.

Do not use wound dressing on pruning wounds. Although wound dressing was once considered a pruning essential, research has shown that paints and sealers do not prevent decay (some actually foster it) and do not speed recovery from wounds.

Timing

Pruning during the dormant season has a different effect on plant growth than pruning during the growing season. Pruning of any kind causes stress, which is why careful pruning at the right time and for the right reasons is important. Here are some of the factors to keep in mind when timing a pruning project: Nitrogen/carbohydrate balance. Pruning removes stored carbohydrates, and for evergreens and other plants pruned in summer, it also removes the leaves, which produce carbohydrates. This affects the plant's nitrogen/carbohydrate balance. The changed relationship — less carbohydrate and more nitrogen — encourages vegetative growth (stems and leaves) rather than reproductive growth (flowers and fruit). Root pruning, in contrast, increases the amount of carbohydrates in relation to nitrogen in the plant, thereby increasing flowering or fruiting.

Dormant-season pruning. Trees are especially affected by dormant-season pruning because they store energy (carbohydrates) over the winter in the trunk and roots. Shrubs store energy in their roots, crown, and (to a lesser extent than trees) aboveground stems, so they react somewhat differently than trees do. If a tree's top growth is pruned too heavily, the stored carbohydrates, the amount of which remains relatively unchanged, cause the tree to respond with a growth spurt once the growing season begins. With the same amount of energy, but fewer outlets (branches) to receive that energy, the branches that remain grow more than they would have if the tree were unpruned. This primarily fosters vegetative growth instead of wood that produces flowers and fruit.

Growing season pruning. Pruning during the growing season eliminates leaves, which are an energy source. This tends to slow the growth of the plant. Use thinning cuts in summer to remove watersprouts and other excessively vigorous vegetative growth produced during the current season. To minimize winter injury, stop pruning by midsummer to make sure that all new growth has a chance to harden off before the dormant season begins.

Timing rule of thumb. Part 2 of this book contains specific timing recommendations for a wide variety of plants. If you don't know the name of the plant you are pruning, use this simple rule from biologist and plant pathologist Dr. Alex Shigo: "Avoid pruning when leaves are forming or in the fall when they are coloring and dropping." That will not keep you from pruning a plant that bleeds at the wrong season, but it will keep you from harming your plants.

Prune Hard for Growth

Pruning can be counterintuitive. On a plant with lopsided growth, remember this rule: To encourage weak branches to grow more vigorously, prune them hard; to slow down the growth of already vigorous branches, prune them lightly if at all. Weak, spindly branches will not produce many flowers or fruit and therefore should not be left intact. Rampant growth tends to be primarily vegetative, meaning it produces lots of foliage and branch length, but few flower buds and thus little fruit. Your goal should be to balance growth across the entire plant.

Apical Dominance

The bud at the apex, or top, of a young tree or at the tip of any shoot exhibits an effect called apical dominance that influences the way the rest of the plant or shoot grows. Called the apical bud, it grows more vigorously than other buds farther down the stem, and it also releases plant compounds called auxins that inhibit buds farther down the stem from sprouting. The amount of influence varies: the bud at the tip of a young, unpruned sapling generally exhibits more apical dominance than a bud on the tip of a side shoot, for example. Apical dominance also varies among species: it is strong in some and has less influence in others.

Pruning techniques are strongly tied to apical dominance. Cutting off the top of a sapling or the tip of a shoot eliminates the auxins that the top bud was releasing. When the topmost bud is removed, the bud that is immediately below the removed tip generally becomes the new dominant bud, although several buds toward the top of the new stem also can begin to grow and compete with one another. The new dominant bud (or several buds competing for dominance) begins to excrete auxins that influence growth farther down the stem.

Apical dominance is the reason it's important to prune above a bud that is pointing in the direction you want new growth to grow. If you make pruning cuts above buds that are pointing toward the center of the plant, new growth will result in branches that crowd the center. If you clip above outward-pointing buds, new growth will grow outward. Note that in some species, leaf buds can be very small, so look closely.

Keep apical dominance in mind when shaping trees. If the apical bud at the tip of a tree's main stem, or leader, is damaged or removed, remaining buds or branches at the top of the tree will begin to compete with one another for dominance, resulting in several vertical branches. If left unpruned, these vertical branches will result in codominant stems, often joined to the main leader by weak, narrow crotches, or branch angles. To reestablish a central leader, select one of the competing branches and use thinning cuts to remove its competitors. Retain branches farther down the stem that have wider, stronger crotch angles to establish a branching framework for the tree. Cut these branches back by one-third to one-half if they are vigorous and might compete with the central leader.

Here are some other effects of apical dominance to keep in mind: Horizontal branches exhibit less apical dominance than vertical ones. Tying a branch down so that it is at a more horizontal angle lessens the effects of apical dominance. For example, tying vines so that they run horizontally along wires or training the branches of a fruit tree so that they are horizontal, or nearly so, encourages the production of flowers and fruit.

Apical dominance is strongest in young plants and young shoots. As trees near maturity, they tend to branch more as apical dominance lessens. This allows the production of flowers and fruits or seeds.

Pruning Cuts

There are two types of pruning cuts: thinning cuts and heading cuts. Both are used whether you are pruning a tree, a shrub, or any other plant. They have different effects on plant growth, and both can be used badly or well. For the best pruning results, think about the proper way each cut is made as you work, and make each cut carefully.

Thinning Cuts

Nearly all of the pruning cuts you will need to make are thinning cuts. These remove a branch or stem by cutting it off at the point where it originated, meaning where it joins to the trunk of a tree or any other branch. By using thinning cuts to remove stems, side branches, or entire branches, you follow a plant's growth pattern and produce plants that look the most natural and require the least amount of pruning maintenance.

Thinning cuts are the appropriate choice for removing dead or diseased branches and for eliminating branches that rub one another or that cross the center of the plant. Thinning cuts are quite useful for opening up the center of a plant so that the plant receives more light and air; they are also useful for eliminating branches that are growing in an awkward direction.

Thinning Cuts Step by Step

When removing branches from a tree, always use a three-step process to make thinning cuts. Cutting straight through a branch in one go can cause major damage: if the branch falls before the cut is finished, it can tear bark down the trunk. Keep in mind that removing branches when they are still small is best for the tree, as small wounds compartmentalize quicker than large wounds do.

Before you cut, identify the branch collar and the branch bark ridge, which mark the location of the branch core within the tree (see illustration below). Make all cuts outside the branch collar and the branch bark ridge, both of which should be left intact for proper wound compartmentalization.

1. Make a shallow cut on the bottom of the branch, about 12 inches outside the branch collar. This prevents the branch from falling and tearing bark down the trunk while it is being cut.

2. Cut off the branch, this time from the top, about 2 inches outside the first cut.

3. To remove the remaining part of the branch, cut from the top just outside the branch collar.

When pruning shrubs or removing small tree branches that arise from other branches, use a small pruning saw, bypass loppers, or bypass hand pruners (depending on the size of the branch being removed) to clip off the branch outside the branch collar. The branch collar is more difficult to see in shrubs and small branches than in large tree branches, but cuts that leave it intact will allow the plant to compartmentalize the wound most effectively.

If you are using bypass loppers or bypass hand pruners (see Hand Pruners), position the tool so that the wide, convex cutting blade is next to the main branch. This ensures that your cut is made just outside the branch collar. If the narrow, concave bottom blade is next to the main stem, the cut you are making will be slightly outside where you intend it to be. Either approach the branch from the opposite direction or turn the tool upside down so that the cutting blade is next to the main stem.

Thinning cuts sometimes cause shoots to form near the cut (severely so if you cut into the branch collar). Watch for these and remove them when they are very young, either by rubbing them off or clipping with pruning shears.

Thinning Cut Mistakes

Making flush cuts that damage the branch collar, removing large limbs, and leaving stubs on every cut are all pruning mistakes that make it easy for disease organisms and other problems to invade a tree.

Plant Choices and Pruning

To reduce the amount of pruning your plants require over their lifetime, consider the following:

* Before you plant, know what size new trees, shrubs, and other plants will reach at maturity. To eliminate the need to prune to reduce size, site accordingly. Don't forget to accommodate mature width when planting next to pathways, driveways, other access routes, or other plants. Planting too close to a walkway is a common mistake; plants sited in this manner will need regular pruning to keep them from encroaching on the walkway.

* Do not plant tall trees under power lines. As a general guideline, when planting within 30 feet of a power line, stick to shrubs and trees that are 20 feet or less in height at maturity.

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Excerpted from "How to Prune Trees & Shrubs"
by .
Copyright © 2016 Barbara W. Ellis.
Excerpted by permission of Storey Publishing.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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