Pruning advice | Part 3
Copyright 2005 - 2011 by M. D. Vaden. Pruning information is divided into Part 1, Part 2, Part 3, Etc. - plus other pruning topics.
Pruning Part 3
Pruning cuts should be made so that only branch tissue is removed and stem tissue is not damaged. At the point where the branch attaches to the stem, branch and stem tissues are separate, but contiguous. If only branch tissues are cut when pruning, the stem tissue within, should decay very little and the wound will seal more effectively.
To find the proper place to cut a branch, look for the branch collar that grows from the stem tissue at the underside and edges of the base of the branch (where the branch meets the trunk).
On the upper surface, there is usually a branch bark ridge. A small chunk of bark on the top side of the branch near or next to the trunk. A proper pruning cut does not damage either the branch bark ridge or the branch collar.
A proper cut begins just outside the branch bark ridge and angles down away from the stem, avoiding injury to the branch collar. An image is included to show the cut needed for a small branch and for a larger branch which may need 3 cuts total for the pruning removal.
Make the cut as close as possible to the stem, but outside the branch bark ridge so that stem tissue is not injured and for the wound to seal with new tissue in the shortest time possible. If the pruning cut is too far from the stem leaving a stub, the branch tissue usually dies and woundwood, a callous, forms but does not close over as well if at all. When stubs are left, wound closure is delayed because the woundwood must seal over the stub that was left.
When pruning small branches with hand pruners, make sure the tools are sharp enough to cut the branches cleanly without tearing. Branches large enough to require pruning saws should be supported with one hand while the cuts are made. If the branch is too large to support, use a three cut pruning procedure to prevent bark ripping.
1. The first cut is made on the underside of the branch outside the branch collar. This cut will prevent a falling branch from tearing the stem tissue as it pulls away from the tree. 2. The second cut should be outside the first cut, all the way through the branch, leaving a short stub. 3. The stub is then third cut just outside the branch bark ridge/branch collar.
Prune dead branches much the same way as live branches. Making the correct cut is usually easy because the branch collar and the branch bark ridge can be more evident. Make the pruning cut just outside of the ring of woundwood tissue that formed, being careful not to cause unnecessary injury. Large dead branches should be supported with one hand or cut with the three-step method, just as live branches.
Topping is a practice or malpractice that harms trees and should not be used. Crown reduction pruning is the preferred method to reduce the size or height of the crown of a tree, but is rarely needed and should be used infrequently.
Conifers may be pruned any time of year, but pruning during the dormant season may minimize sap and resin flow from cut branches. If the sap won't drip on a sidewalk or something, this may be inconsequential. I prune conifers all 12 months.
Hardwoods and shrubs can be pruned in the dormant season to easily visualize the structure and discourage some sap flow from wounds, although its rarely a problem. In particular, wounded elm wood is known to attract bark beetles that harbor spores of the Dutch elm disease fungus, and open wounds on oaks are known to attract beetles that spread the oak wilt fungus. Usually, the best time for those, is during the late fall and winter. White birch may be something to avoid pruning in June and July. In general though, moderate thinning and pruning can be done all year.
Tree sap, gums, and resins are the natural means by which trees combat invasion by pathogens. Sap flow from pruning wounds is not generally harmful; however, excessive oozing of sap can weaken. In most cases, you won't see dripping prolonged to the point of being excessive. The drips often stop in a matter of days to a couple of weeks. An important thing to remember with this sap flow is that the movement of moisture has not really changed. Call inside the trunk trunk Point A, and the length of the Branch Point B. Before a pruning cut, water was moving from Point A to Point B. After the cut the situation is basically the same. Call inside the trunk Point A, and the exterior of the pruning cut Point B. Now what's happening? Water or sap is still moving from Point A to Point B ... maybe a bit faster, but not bad.
When oaks or elms are wounded during a critical time of year (usually spring for oaks, or throughout the growing season for elms) -- either from storms, other unforeseen mechanical wounds, or from necessary branch removals -- some type of wound dressing should be applied to the wound. Only for those two - but not others species. In general, pruning wound dressings do more bad than good. In the case of elm and oak, the harm from not using the dressing, exceeds the harm of using the dressing. Do this immediately after the wound is made. Wound dressings will not stop decay. They can interfere with the protective benefits of gums and resins, and prevent wound surfaces from closing as quickly as they might under natural conditions. The only benefit of wound dressings is to prevent introduction of pathogens in the specific cases of Dutch elm disease and oak wilt.
If you want to become good at pruning, there are a few things you should do - wiith today's resources, you should:
1. Read, borrow or buy a good pruning book with illustrations or photos. 2. Get coaching from someone that understands pruning. 3. Attend a class or seminar.
Most people won't become excellent at pruning. But anybody who learns more can become better than they were. Many people can become good at pruning. Proper pruning extends the life of plants, shrubs, softwoods and hardwoods, and controls growth.
In general, there is no perfect time of year to prune. An expert with trees has written that the perfect time of year to prune is right after leaves appear and right after leaves fall. But he also indicated that pruning can be done almost any time of year. In the context of his pruning chapter, that means moderate pruning can be done almost any time of year. The expert was Dr. Shigo, who was a consultant, and previously the head scientist of the US Forest Service.
There are several shrubs that should not be pruned at just any month. For example - lilac. Lilac will bloom the next spring on what was new growth from the previous summer. Lilac should be pruned soon after flowers fade if you need to reduce the top bulk. This does not mean you need to cut and top of every stem on the entire plant. We have a pruning time table for many shrubs at the bottom of this page.
Since many shrubs flower, and are not planted to become tall, it will be important to identify each genus and species, and read information about how to prune for the particular needs and blooming times.
Conifers and hardwoods are a bit different because although several will produce showy flowers, many people avoid topping those allowing for upward growth. Tips that produce flowers are unlikely to be pruned.
20% removal of foliage / canopy is a decent guideline for shrubs as well as trees - try to remove 20% or less. Any more may have negative effects. This is primarily in reference to plants that we want to preserve for decades. Certainly you will see people remove 45% off the top of apple or shear 40% off the top of a hedge, but that's different from training and coordinating the growth of a large ornamental specimen for typical landscape and garden needs.
Pruning in fall will not hurt. Some people will tell you not to prune in fall because pruning stimulates growth, and that autumn pruning will start a flush of irreversible growth as the season progresses into cold weather. I defy you to fight a conifer's or hardwood's ability to go dormant by way of pruning if pruning is done moderately. Now ... roses ... that may be the one exception that comes to mind. I seem to recall some tender shoots in autumn resulting from early September pruning. But the end result in winter was not disasterous, usually some shriveled tips which often are pruned off at winter's end anyway.
After years with pruning entire golf courses, regions of university campuses, and 100s of residential locations, I don't recall seeing a flush of growth in autumn. Because it is very hard to fight nature, especially when pruning moderately. At least 2 other factors cause trees to go dormant:
1. Reduced temperatures.
2. Reduced day length.Pruning in fall cannot control temperature or day length. If you recognize a need to prune, then the best time to prune is usually when you recognize that need. Other than a few pruning exceptions, that's one of the best answers to the common question: "when is the best time to prune?"
Rose pruning: roses are often pruned lightly in fall or early winter to remove a bit of weight off the top. That keeps them tidy, and reducing swaying caused by wind rocking the conopy. Then, the following February or March, those rose plants are pruned more completely by thinning or reducing cane length as needed.
Whatever you prune, keep sunburn in mind. We have a complete page about sunburn. If you remove top foliage from a plant in summer, realize that you are exposing bark or other leaves below to a greater intensity of sunlight. That can cause sunburn. If removal of top foliage in summer can wait, please do so. This pertains strongly to some fruit pruning, renovating plants / shrubs, and reducing hedge height.