Mouse Garden

Thursday, 12 February, 2009

Basic Rules For Trimming Fruit Trees

Filed under: Garden,Trees — Admin @ 17:39

From: http://www.greenharvest.com.au/greennotes/Winter.html

Begin pruning fruit trees about one month before start of their growing season. Early summer pruning has become common and has improved benefits for training young trees as it allows for smaller cuts with less stress to the tree. This is only commonsense, if you allow an undesirable branch to grow all summer. Trimming tree in late fall or winter means a much greater wound for the tree to heal. Summer pruning can often be done just by ‘rubbing off’ an unwanted bud with your fingers. Always avoid pruning on rainy days, as dry weather aids in healing the cuts.

Fall and winter is still a good time to do fruit tree maintenance, such as removing deadwood or crossing branches. Begin by preparing your tools, sharpening secateurs and loppers and apply linseed oil to any wooden handles. The correct tools make the job easier, the basics you need are: secateurs for small, precise cuts, loppers for removing suckers, especially thorny ones and a good quality pruning saw for the bigger branches.The only really safe ladder for outside work is a 3-legged orchard ladder, with foot pegs that push into the ground. Safer still is keeping fruit trees pruned low, as the fruit will be within easy reach for foliar feeding and harvesting and there is less risk of a fall. Remember your aim in pruning in a home garden is different to that of a commercial grower. It is essential you keep the tree small and manageable, so it can be covered easily to protect the fruit from birds, bats and possums; and in many areas, from fruit fly.How to begin:

  • Step back from the tree and try to see the main branch structure that you need to develop. It is a good idea if you are new to pruning to make a habit of regularly stepping back as you work, to see the tree as a whole. Your aim is primarily thinning the branch structure rather than just shortening every branch.
  • Begin by removing all dead or damaged wood, as well as suckers from below the graft. Clear away soil around the suckers and cut as low as possible to prevent a re-appearance.
  • Next remove branches growing towards the center of the tree. These are generally not fruitful and tend to harbor pests and disease. Over-crowding also prevents entry to the center of the tree by insect eating birds. Always remove branches that are rubbing together. Step back and take another look.
  • Aim to prune out narrow-angled branch crotches, as these harbor pests such as borers and can break under the weight of fruit; a 60° angle where any branch joins the main trunk is best.
  • Shorten back last season’s growth; general rule is “if I can’t reach it, I cut it off”. Tall fruit trees usually just end up feeding the birds. Most fruit trees can be kept under 3m in height.
  • Finish up by removing loose bark with a wire brush; this will help destroy over-wintering two-spotted mite and codling moth grubs.

From: http://www.ces.ncsu.edu/depts/hort/hil/ag29.html

Pruning vs. Training
Historically, fruit tree form and structure have been maintained by pruning. Tree training, however, is a much more efficient and desirable way to develop form and structure.
Pruning is the removal of a portion of a tree to correct or maintain tree structure. Training is a relatively new practice in which tree growth is directed into a desired shape and form. Training young fruit trees is essential for proper tree development. It is better to direct tree growth with training than to correct it with pruning.
Pruning is most often done during the winter, commonly referred to as dormant pruning. Training includes summer training and summer pruning as well as dormant pruning. The goal of tree training is to direct tree growth and minimize cutting.


Dormant Pruning vs. Summer Pruning
Trees respond very differently to dormant and summer pruning. Dormant pruning is an invigorating process. During the fall, energy is stored primarily in the trunk and root system to support the top portion of the tree. If a large portion of the tree is removed during the winter, while the tree is dormant, the tree’s energy reserve is unchanged. In the spring, the tree responds by producing many new vigorous, upright shoots, called water sprouts, which shade the tree and inhibit proper development. Heavy dormant pruning also promotes excessive vegetative vigor, which uses much of the tree’s energy, leaving little for fruit growth and development.
Historically, much of the vigorous, upright vegetative growth has been removed during the dormant season; heavy dormant pruning results in a yearly cycle with excessive vegetative growth and little or no fruit production.

Timing of dormant pruning is critical. Pruning should begin as late in the winter as possible to avoid winter injury. Apple and pecan trees should be pruned first, followed by cherry, peach, and plum trees. A good rule to follow is to prune the latest blooming trees first and the earliest blooming last. Another factor to consider is tree age. Within a particular fruit type, the oldest trees should be pruned first. Younger trees are more prone to winter injury from early pruning.

Summer pruning eliminates an energy or food producing portion of the tree and results in reduced tree growth. Pruning can begin as soon as the buds start to grow, but it is generally started after vegetative growth is several inches long. For most purposes, summer pruning should be limited to removing the upright and vigorous current season’s growth; only thinning cuts should be used. To minimize the potential for winter injury, summer pruning should not be done after the end of July.


Types of Pruning Cuts
Thinning Cut – removes an entire shoot back to a side shoot. Thinning cuts do not invigorate the tree in comparison to some of the other pruning cuts.
Heading Cut – removes only the terminal portion of a shoot. This type of cut promotes the growth of lower buds as well as several terminal buds below the cut. When lateral branches are headed into one year old wood, the area near the cut is invigorated. The headed branch is much stronger and rigid, resulting in lateral secondary branching. Older trees can be held in their allotted space by mold and hold cuts, which are devigorating heading cuts made into two year old wood. Young trees and branches where heading cuts are made will be referred to as headed.
Bench Cut – removes vigorous, upright shoots back to side branches that are relatively flat and outward growing. Bench cuts are used to open up the center of the tree and spread the branches outward. This is a major cut and should only be used when necessary.
When making pruning cuts, it is important to use techniques that will allow the cut surface to heal quickly. Rapid healing minimizes the incidence of disease and insect infection. Pruning cuts should be flush with the adjacent branch without leaving stubs. Also, when large horizontal cuts are made, they should be slightly angled so that water does not set on the cut surface, allowing the growth of rot and disease organisms.
Many compounds are available as wound dressing or pruning paints. But the best treatment is to make proper pruning cuts and allow the tree to heal naturally. If preferred, tree paints and wound dressing may be used for aesthetic reasons, but they will not promote healing.


Training Systems
One of the most frequently asked questions is, “To what shape should I train my fruit tree?”
It is difficult to give one answer. You can choose from many different training shapes and forms with multiple variations on each form. A fruit tree may be trained to any system. Depending on the form and function of the desired shape, you may want to train a tree to a nontraditional system.
Whatever system is chosen, keep in mind that the objectives of training and pruning are to achieve maximum tree life and productivity.


Central Leader Training – Apple, Cherry, Pear, Pecan, Plum
A central leader tree is characterized by one main, upright trunk, referred to as the leader. Branching generally begins on the leader 24 to 36 inches above the soil surface to allow movement under the tree. The first year, 3 to 4 branches, collectively called a scaffold whorl, are selected. The selected scaffolds should be uniformly spaced around the trunk, not directly across from or above one another. Above the first scaffold whorl, leave an area of approximately 18 to 24 inches without any branches to allow light into the center of the tree. This light slot is followed with another whorl of scaffolds. Alternating scaffold whorls and light slots are maintained up the leader to the desired maximum tree height. See Figure 1.
The shape of a properly trained central leader tree is like that of a Christmas tree. The lowest scaffold whorl branches will be the longest and the higher scaffold whorl branches will be progressively shorter to allow maximum light penetration into the entire tree.
Developing a Central Leader Trained Tree At Planting
Fruit trees are frequently purchased as whips, which are unbranched trees ranging from 1/2 to 3/4 inch diameter. The tree should be planted in early winter with the graft union 2 inches above the soil surface. Just before the buds start to grow in the spring, the tree should be headed, or cut off, at 30 to 34 inches above the soil surface. The height at which the tree is headed depends upon where you want the first whorl of branches. Once the tree is headed, permanent branches will be selected from buds growing within 4 to 12 inches below the heading cut. See Figures 1 and 2.


Figure 1. Pruning a central leader treeAt Planting
As the buds begin to swell, head the tree at 30 to 34 inches above the soil surface.Dormant Pruning
Head the tree at 24 to 30 inches above the highest branch of the first scaffold whorl.Top ViewFirst-Year Summer Pruning
Summer prune when new growth is 3 to 4 inches long. Leave a as the new leader, and remove b and c. Select four uniformly spaced laterals for the first scaffold whorl, and remove the remaining lateral branches.After pruning the third year
Three scaffold whorls have been developed with three to four branches uniformly spaced around the tree in each whorl. A light slot of 18 to 24 inches is left between each scaffold whorl. Note the Christmas-tree shape that allows light penetration to the lower branches and interior of the tree.Steps in Pruning:

  • Leave only one trunk for the central leader.
  • Remove branches with crotch angles less than 60 degrees.
  • Remove all branches directly across from one another on the leader.
  • Space lateral branches uniformly around the leader to prevent crowding as the limbs grow in diameter.

Summer Pruning
After the new vegetative growth has reached 3 to 4 inches in length, summer pruning should begin. The first step is to select one upright shoot near the top of the tree to be the leader. After selecting the leader shoot, remove all other competing shoots for approximately 4 inches below it; rehead the tree above this leader. See Figures 3 and 4.


Figure 3.
     Left: Heading an apple tree at planting results in several competing shoots below the cut.
     Right: For central leader tree, a single leader needs to be selected by removing the undesired shoots.


Figure 4. Central leader plum trees must also have competing shoots removed.


At this time, side shoots (laterals) should be spread out to form an angle of 60 to 70 degrees between the leader and the side shoot. This angle is referred to as the branch or crotch angle. Branches that do not have a wide branch angle are overly vigorous and have a weak point of attachment to the leader. These branches frequently break under a heavy fruit load. Spreading the lateral branches will also slow the growth of the branches to a manageable level and promote the development of secondary or side shoots on the scaffolds. When growth is only 3 to 4 inches, toothpicks or spring clothespins can be used to spread branches. See Figure 5. After a proper branch angle is attained, clothespins can be moved to the ends of longer limbs to weigh down the branches as they start to grow upward.


Figure 5. Central leader apple trees. Toothpicks are used to spread the lateral branches outward during the first growing season.


During the first year, minimize further summer pruning. Limit it to the removal of shoots growing upright or downward. Summer is the optimal time to select the leader and scaffold branches and remove undesirable growth. Branches lower than the desired height should also be removed. A young orchard or tree should be summer trained and pruned once a month through July to remove unwanted growth and to properly orient young branches. Summer pruning will greatly reduce the amount of dormant pruning needed.
Failure to summer prune the first year will result in an improperly trained tree, and drastic dormant pruning will be required to correct tree structure.
Succeeding Years
Managing the central leader is one of the most important aspects of dormant pruning. The leader should be headed at approximately 24 to 30 inches above the highest whorl of scaffolds to promote continued branching and scaffold whorl development. Dormant pruning should also eliminate dead, diseased, and damaged wood. Unwanted growth, such as upright growing shoots and laterals with sharp branch angles not removed during summer pruning, should also be removed at this time. Unbranched lateral branches should be headed back by approximately 1/4 of their length to encourage side branches and to stiffen lateral branches.
Summer pruning in succeeding years should eliminate competing shoots where dormant heading cuts were made (on the central leader and laterals) as in the first year. Summer is also the optimal time to remove unwanted side shoots and excessive growth. All laterals should have a wide branch angle, and spreading of lateral branches is essential for many varieties. Lateral branches will need to be spread for about the first five years, using a larger spreader each year.
Spreaders can be made with 1inchsquare wood pieces with a finishing nail driven in the end and cut off at an angle. Spreaders are frequently made in lengths of 6, 12, and 18 inches. See Figure 6.


 

Figure 6. Wooden limb spreaders can be made from wood and finishing nails in various lengths.

Spreading branches in later years reduces vigor and promotes fruit development on the lateral branches. The reduced growth rate and the weight of the crop load will also help pull the branches down to a proper angle. However, it is important that the young tree is not allowed to crop too early where the weight of the fruit pulls the branches below horizontal. Once the branches are below horizontal, they are weak and nonproductive and need to be removed and replaced. See Figure 7.



Figure 7. Well-trained apple trees. Note the branch angles and the development of scaffold whorls.


Another objective of dormant pruning is to control the length of the lateral branches. In order to maintain the Christmas tree shape (Figure 1), lateral branches need to be cut back. Once the tree has reached its desired height and lateral spread, it will be necessary to mold and hold the lateral branches and the central leader with heading cuts. This can be done by cutting the laterals and leader back into two year old wood to a side growing shoot. It is a good rule to cut back to a side shoot that is close to the same diameter as the lateral or leader being cut.

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1 Comment »

  1. You really put a lot into this page.

    The “step back” idea probably is the safest option for many home gardeners with fruit trees or other trees in their landscape.

    After a number of years, I found that the tree can finally be read from the inside as the ultimate method, but it takes a long time to reach the point of visualizing the outward shape by way of the inside structure.

    MDV / Oregon

    Comment by M. D. Vaden of Oregon — Monday, 30 November, 2009 @ 15:30 | Reply


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