Tree Pruning Techniques

Tree Pruning Techniques Overview:

• Most deciduous fruit trees (and many others) will be healthier, stronger and produce better crops with regular thoughtful pruning.
• This article is divided into three main sections. First we will review the top reasons to prune your fruit trees.  Secondly, we will discuss the three most popular training shapes that are used for fruit trees.   Finally, this article will cover the specifics of pruning that are applicable to every tree training technique.

Why do you need to prune your fruit trees?:

Training and pruning is done to make your trees as healthy and productive as possible.  This in large part means creating an architecture for optimal photosynthesis and strength.

Return On Investment (ROI):

Leaves are costly to produce. Therefore, if the tree is going to be successful, it needs to get a good ROI on those costly leaves.  Leaves that are shaded inside a canopy get less sunlight and therefore produce less energy per individual leaf.  Therefore, removing limbs that will be hidden from sunlight will keep the tree from wasting energy on producing leaves on branches that won’t get the best sunlight and ROI.

Disease:

Branches that don’t get optimal sunlight are subject to prolonged moisture and therefore fungal infection.  Poor air circulation in a crowded interior canopy can also compound the moldy problem.   This crowded-shaded environment is also a great breading place for sap-sucking bugs like aphids and spider mites.  Crossing branches can also rub against each other, damaging the protective bark and therefore predisposing to additional disease.

Support:

Weak and poorly structured branches may also break from the weight of fruit.  These broken branches may also be a pathway for infection into your tree.

 

Three most popular tree training shapes:

There are many different tree structures that you can create with pruning, and each has its merit for different situations.  The three most common tree pruning structures that I use are “central leader”, “open center” and  “espalier.”  However, depending on my particular needs and the location, I may create a hybrid of different shapes/structures.

Central leader training:

Often used for apples, pears, Asian pears, pecans, and quince. Sometimes also used for plums, nectarines, and peaches.

This is kindof a classic Christmas tree look.  The name comes from the fact that the central trunk is the single leader.  All of the branches come off of that central leader/trunk.  The side branch tiers are also known as scaffold branches.  For optimal light penetration to the lower branches, it is important to make sure there is adequate space between each tier of branches and that the top tier of branches are shorter than the bottom tier of branches.  Trees pruned this way can get big, so some say it is best suited to dwarf/semidwarf trees.

The “central leader training” appearance is also the tree- look that I have used later in this article to demonstrate the branches that you will always want to prune.  These basic pruning principles discussed further down in the article are applicable for every tree training method.

 

 

Open center training:

Often used for apricot, cherry, nectarine, peach, plum, prune, almond, fig, pear, apple and pistachio.

This shape can be used to keep a tree smaller and more manageable for a home garden.   The overall shape of this tree is composed of two main elements. There is a short (cropped) trunk, and there are several main limbs extending outward from the main trunk.  The result is reminiscent of a wine glass or a vase. The idea is to have an open center that gets light and at the same time force growth outward that is easy to access without a ladder.

Getting to this shape will take several seasons.  One way to do it is…

* Dormant season 1: Crop the main trunk to 2-4 feet high.

* Dormant season 2: Prune to leave behind 3 to 5 evenly spaced primary scaffold branches that radiate out from the main short trunk.  Trim these scaffold branches to be 2-3 feet long.  Ideal branch angle from the trunk is about 45 degrees.  For cherry, plum and pear trees that tend to have upright growth, you may have to bend and support young flexible branches to fit the desired shape.

* Dormant season 3: Prune to leave 2 to 3 new lateral branches extending off the primary scaffold branches. Prune these lateral branches to be 2-3 feet long.

 

 

Espalier training:

Often used for apple, fig, loquat, olive, peach, nectarine, plum, almond, pear, and grape (I know, grapes are not a tree).

Espalier is a French word that is derived from the Italian spalliera, meaning “to rest on the shoulder.”

This is a great solution for a thin/narrow space. Basically you are pruning to make the tree look like a flat fan. For this technique you will also need lots of support to help the plant comply with the shape.   Most people use a trellis or a series of parallel horizontal wires to train and fasten the branches to (such as in the drawling above). The branches/wires are often spaced about a foot or two apart.  You can also use stakes to train a tree to grow in the espalier pattern of growth (see picture below).

 

Pruning techniques that apply to all training methods:

Art & science of tree pruning:

There is a bit of an art and science to pruning trees.   However, there are some basic rules to follow and there are some branches you should always remove. Once these classic offending limbs are out of the way, step back and see if you need to do anything more.   On that note, a major key is to know when to stop.  Too much pruning can stress your tree and therefore negatively affect fruiting.   Sometimes it is ok to wait another year before trying to reach “pruning perfection” in one season.   Note; you can sometimes also “fix” poorly oriented branches (and avoid cutting an otherwise healthy limb) by bending and staking young flexible branches to the desired orientation.

Always prune these branches: 

The following outline will describe each of the branches you will nearly always want to prune.  Please see the associated images below for visual reference.

A.   Downward or backward pointing branches: These branches get suboptimal light exposure and are prone to breaking with the weight of fruit.

B.   Water spouts: These branches represent focal rapid growth. The result is a long weak branch that typically crossed other branches.

C.   Dead or diseased branches: When all the leaves have fallen, it can sometimes be hard to tell if a branch is dead until you cut into it. There are a few things that you can do to confirm a branch is dead before removing it.  For example, young healthy limbs typically bend/flex while dead branches tend to be brittle and snap. Making a small cut to the bark of a live branch should reveal a healthy-moist green/yellow under the bark. Another option is to cut a small side branch first to see if it is dead, dry and woody.

D.   Closely spaced branches: The top branch can block out light to the branch below.

E.   Rubbing or crossing branches:  Rubbing branches will result in damage to the bark that can lead to infectious disease. This crossing orientation of a branch is also suboptimal for sunlight exposure.

F.   Narrow crotch:  It sounds a bit profane, but name this just refers to the angle between the trunk and the side branch. The result of this type of a branch is growth inside the canopy with suboptimal sunlight exposure and potentially rubbing branches. These narrow crotch branches can also be weak at the attachment with the trunk.

G.   Sucker growth:  Sucker growth is any growth below the graft union scar. Sucker growth will redirect energy away from the “good fruit” producing part of your tree. If allowed to continue, this sucker growth can also completely takeover a tree.

Graft union scar definition: The graft union scar is often visible as a circumferential change in the diameter of the trunk.  The scar is sometimes also noticeable by a subtle change in the appearance of the bark and the leaves of that sucker growth may look different from the rest of the tree.

 

When to prune your trees?

There are two basic times to prune you trees.  Dormant-season and Summer pruning.

Dormant (winter) season pruning:

With all the leaves out of the way, it is usually much easier to see what you are doing.  Trimming in the winter is also great because the tree has not invested energy into producing the leaves on those branches your about to cut off.

After you prune in the winter is also a perfect time to spray the branches and buds for parasitic bugs. I use simple horticulture oil to kill overwintering bugs this way. This is perhaps the most cost effective method of sap sucking pest control.  I always label my garden sprayer so I don’t use a bottle with the wrong residue left inside that may harm a plant such as weed killer. I have been using the larger than standard 2 gallon spray bottles to avoid multiple refills and therefore save time.

Many deciduous trees will also benefit tremendously from fungal spray treatment to the buds before they open. For example, in the case of peach leaf curl, you must spray the buds before they open up in the spring/late winter.  If you spray after the buds open then you missed your window and it is too late; spraying the infected leaves will do little to peach leaf curl.  There are a lot of fungicide options, but I have had a lot of success with copper fungicide that I use in my garden sprayer.

Summer pruning:

This is the time to do touch up work like removing dead branches, diseased branches and sucker growth.

 

How to make the pruning cuts?

How to cut the branch:

It is important not to make the cut too close to the trunk.  Cutting too close to the trunk and the branch collar can open up the wood to decay. The best option for me has been to cut the branch about a quarter inch from the side branch leaving a little nub behind.  I also like to make my cut at a bit of an angle and in such a way that the cut flat surface is not parallel to the ground.   In theory, this type of cut-orientation will help to keep the cut end from collecting too much water after a rain.  For large cuts, some advocate using a sealant to keep bugs out. However, many of the academic agricultural people say you should not use sealants because it will trap moisture which will lead to disease.

Sharp tools:

One of the most important things you can do is to make a clean cut. If your cutting tool is dull or if the blade hinge is loose, then the bark can get macerated.  This rough cut end of the branch can predispose the tree to disease.  In addition, a macerated close cut can even stimulate limb die-back in the absence of an obvious infection.

An easy way to sharpen a garden tool like a pruning shear is to use a Dremel type rotary tool.  I see there is a cordless Dremel with great reviews on amazon that comes with a garden sharpening bit.  I think I would have gotten this one if I saw it earlier.  However, I happen to have a Black & Decker rotary tool, because it was cheaper and on sale at the time.  This Black & Decker option has not given me any problems and it is basically the same thing as the Dremel brand tool except that it has a cord.  You will have to buy a separate garden tool sharpening kit with a basic package such as this Black & Decker option.

Pruning shears:

I always use anvil type shears (the blade cuts down against a flat surface).  Anvil shears are a great all around trimming/pruning tool. However, tiny branches can also be cut with bypass shears (two blades pass each other like scissors).

I have personally gone through many-many different pruning shears.  They just kept braking, pulling apart or giving me a headache in one way or another.  However, about a year ago I bought a pair of Corona brand shears on Amazon.  I could not be happier with them; they are easily the best pruning tool that I have ever used and they are not showing any sign of slowing down.

I also got one of those side holsters for the shears that I should have gotten years ago. This holster makes the experience of pruning so much nicer.  I cant personally say if one holster brand is better than another, I just went with Corona again because I didn’t want to take a chance with poor quality again. Besides, the reviews were great on Amazon. If you want to check out this pruning shear holster, I also got this Corona Scabbard on Amazon.

Notice: Be warned, many other brands will try to make their shears look like the Corona brand.  I have actually broken many of these inferior look-a-likes that I have purchased at the big box stores.  The knockoff quality is really no match.

 

Pruning for fruit:

The age of a particular branch will have a direct impact on its ability to produce fruit.  As a result, you want to prune with this in mind; pruning to allow branches of different ages that will ensure fruiting for seasons to come.  In addition, this branch age to fruit phenomenon is a little different for each type of tree.  UC Davis has a nice chart that summarizes the expected fruiting age of a branch for the most common deciduous fruit trees (see below).