Pruning tips, Pruning advice
Text Copyright 2005 - 2007 by M.D. Vaden
References include: ISA Study Guide and the USDA Forest Service.Maybe the best single pruning tip I can offer is on my pruning tools page, about using hand pruners and a quality pruning saw.
The information below is a most basic pruning guide to avoid pruning the wrong way once you have pruning equipment in hand. There are reams of great pruning advice already online and in books. I wrote the brief pruning information because some pruning guides won't mention some of the tips. A pruning schedule for some shrubs is included. Consult several articles and pruning books. The more tips you learn the better.
Reasons for pruning include safety, health, aesthetics, access and scenic views. Pruning can increase fruit production, and the value of timber by improving wood quality. Proper pruning involves removing little defects before they grow into big problems. And in my experience, leaving plants to themselves like nature is unwise. When you hike in the woods, what you see are the survivors, not the ones that split, broke and died. That's why nature puts decay fungi to work too. In a garden or urban setting, we want a high rate of survival, and pruning helps meet that desire.
Pruning for safety involves removing branches that could cause injury or damage, trimming branches that interfere with visual safety at driveways, and pruning away branches that grow into utility lines (pros). Pruning for health involves removing diseased or insect-infested wood, thinning the crown to increase airflow, and removing crossing and rubbing branches. Pruning can best be used to encourage and develop a strong structure and reduce the likelihood of damage during severe weather.
Removing broken or damaged limbs encourages wound closure, because the useless parts won't remain in the way of the tissue that's trying to close-over the wound. One more reason not to leave the plant to itself like in a natural woodland.
Proper pruning is accomplished much easier with the right pruning tool for the job. Review selecting pruning tools.
When deadwood and excess branches are thinned from inside the canopy, more filtered light can penetrate the canopy. This allows light to reach perimeter foliage in a back-lit fashion.
The remaining foliage will benefit from the extra light. If understory plants are under the main foliage canopy, those will acquire more light also. Pruning for aesthetics involves enhancing the natural form and character of plants or stimulating flower production.
Most woody plants shed foliage and branches in response to shading and competition with other shrubs, hardwoods and conifers.
After branches fall, the openings are sealed by woundwood (callus). Branches that are poorly attached may be broken off by wind, accumulation of snow and ice or even animals like raccoons.
Branches that don't produce enough carbohydrates from photosynthesis will die and are eventually shed by decomposing and falling off. If those limbs are large enough, a hazard may result. Later, visit our page with photos and information about Signs of Hazards
Even accumulated water weight from winter rain can bring big branches down. Branches removed by natural forces often get ragged wounds that don't seal or naturally compartmentalize with new tissue. Pruning can supercede and replace these natural processes and increase the strength and longevity of plants. Nature does not prune or care for plants to meet the needs of people. We need to prune to meet personal needs and reduce hazards. And keep in control of the growth.
Proper prunng means canopies can be shifted and directed very effectively. By removing leaders growing toward a building, and leaving other main stems, the form can be directed away from the structure. This is why nature should not be replicated in all ways at all times.
Plants that stand alone and can grow outward in all directions are often a bit easier to prune. One specimen like that is this Mt. Fuji Flowering Cherry.
Woody plants in a natural environment like a forest, are not directed in a way that pruning can offer. In a forest, plants will bend and grow toward light a little. Thats due to plant cells elongating on the dark side of the stem and "pushing" the plant toward light.
In this diagram, blue higlights indicate branches that could be removed to provide an adequate crown thinning. It takes some thought, but the simplicity of bicycle spokes can be a good example to think about. Spokes are evenly spaced, radiating outward. The difference with a tree, is that the growth is not as perfectly arranged as wheel spokes.
Also, branches radiate outward and upward. But the concept is applicable. We don't want a bunch of criss-crossing branches. A woody plant needs pruning to remain somewhat orderly and organized.
Woody plants with pyramidal crowns like many conifers or evergreens, have a strong central stem and lateral side branches that are more horizontal, and do not compete with the central stem or trunk for dominance. With spherical crowns, like many hardwoods, lateral branches may compete for dominance more. Look at some maples for example, which have several leaders and large limbs all reaching upward in different directions.
To reduce the frequency of pruning, its best to consider the natural form of plants for planting and pruning care. It is very difficult to impose an unnatural form on a woody plant without an increase to maintenance. The more we fight nature, the greater our pruning workload.
Proper pruning cuts are made at a node, the point at which one branch or twig attaches to another. In the spring of the year growth begins at buds, and twigs grow until a new node is formed. The length of a branch between nodes is called an internode. A common types of pruning is Crown thinning, primarily a term for hardwoods. It is selective pruning removal of branches to increase light penetration and air movement throughout the crown. This type of pruning maintains or develop structure and form. To avoid unnecessary stress and prevent excessive sprouts, no more than 25 percent of the living crown foliage and bulk should be removed at a time. If it is necessary to remove more, it should be done over successive years. If a specimen is older, like 50 years or more, remove less at one time, like 15 percent of the living crown. Deadwood removal is virtually without limit.
Branches with strong U shape angles of attachment should be retained. Branches with narrow V shape angles of attachment often form included bark which should be removed if available, preferably when younger. If V attachments are not removed at youth and the stems get large, we may have no choice but to retain them.
Included bark forms when two branches grow at narrow acute angles next to one another, producing a wedge of inward rolled bark between them. The bark is folded inward tightly. Pinched in between. Included bark prevents strong attachment of branches, often causing a crack or split at the point where the branches meet between them. The weakest of that kind can peel apart like a banana peel coming off. Codominant stems are present when the trunk or stem divides into two leaders, side by side. Codominant stems from the same position often form included bark. But occasionally U shape unions which are better and stronger. Removing some of the lateral branches from one codominant stem can reduce its growth enough to allow the other stem to become dominant. Later, that less vigorous stem can be removed or reduced more. That strategy works best when the plant is young. Not very practical once age has set in.
Lateral side branches should be no more than one half to three quarters of the diameter of the stem at the point of attachment.
Avoid producing "lion tail," branches, caused by pruning away too much inner twig and and foliage. Lion tails can result in weak branch structure and breakage. Simply put, lion tails occur when too many inner twigs are removed, leaving a tuft or minimual foliage at the end.
Branches that rub or cross another branch should be removed. Remember should be. Some tree pruning needs should be, but need to remain because it can't be - can't be done. Not every correction is possible. More people discuss how to prune away branches than what can't be removed when pruning. And this separates the hack from the master. Just as important as what to prune away, is what not to prune away or when not to prune.
Conifers that have branches in whorls, pyramidal crowns, rarely need crown thinning except maybe to restore a dominant leader or clean some dead branches out. Occasionally, the leader (it's tip) may be damaged and multiple branches may become codominant by curving upward around the break. Or several new ones will sprout from buds and twigs near the break. Select the strongest leader and remove competing branches to prevent the development of codominant stems. These may need to be pruned away over a period of a few years.
Crown raising is the practice of removing branches from the bottom of a tree to provide clearance for pedestrians, vehicles, buildings, lines of site or to develop a clear stem for timber production. The blue highlighted limbs in the image at left indicate branches to remove for this pruning practice.
For street and curbside, minimum clearance is often specified by ordinance, commonly 8' over the sidewalk and 11' to 14' high over the curb and street. This allows delivery and street maintenance equipment to get by.
After pruning, the ratio of the living crown to total height should be at least two-thirds. If you remove lower limbs, no more than the lower third should be removed. Again, emphasis on should. On young conifers and hardwoods, lower branches may be retained temporarily along the stem to encourage a nice trunk taper and protect trees from various activities and sunburn.
Crown reduction pruning is often used when a tree has grown too large for its space. This method, sometimes called drop crotch pruning, is preferred to topping because it results in a more natural appearance, and increases the time before pruning is needed again: minimizing stress and preventing sunburn. Crown reduction pruning, usually a last resort, often results in large pruning wounds to stems that may lead to decay. This method rarely works well for a pyramidal growth form like many conifers have. But I've seen it work out for some like Austrian pine or Japanese black pine. A better long term solution may be to remove the whole organism and replace it with another species that will not grow beyond the available space.
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 > Point A to Point B > 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.
Reasons for scheduling pruning
This season is as good of a season to schedule pruning projects as any other. And your scheduled list can include an extended plan for following seasons. The need of each person will vary, but the needs will include disease control, debris removal capability, crafts, training, appearances and more. The table to the left is a suggested time table for home gardeners, and some of the reason behind it deals with flowering and health. The number code in the table, pertains to the age of growth on which flower buds are produced.
Abelia Nov-Jan 1 Arborvitae (Thuja) Nov-Jul 0 Aucuba Jun-Jul 2 Azalea - Deciduous May-Jul 2 Azalea - Evergreen May-Jul 2 Barberry - Decidudous May-Jul 2 Barberry - Evergreen May-Jul 2 Bayberry Mar-Jun 0 Beautyberry (Callicarpa) Nov-Mar 1 Beautybush (Kolkwitzia) Jun-Jul 2 Boxwood (Buxus) Nov-Jul 0 Broom (Cytisus) Jun-Jul 2 Butterfly bush Nov-Mar 1 Camellia - japonica May-Jul 2 Camellia - sasanqua Mar-May 1 Cherry / Prunus Mar-Jul 0 Cotoneaster - Deciduous Nov-Feb 0 Cotoneaster - Evergreen Nov-Feb 0 Crape Myrtle Jan-Sep 1 Daphne / Winter Apr-Jul 2 Deutzia Jun-Jul 2 Dogwood - Red twig Nov-Mar 1 Eleagnus Nov-Jul 0 Euonymus -Deciduous Nov-Mar 0 Euonymus - Evergreen Nov-Jul 0 Forsythia Apr-Jul 2 Gardenia Nov-Feb 1 Hibiscus / Rose of Sharon Nov-Mar 1 Holly - Evergreen Jun-Jul 2 Honeysuckle May-Jul 2 Hydrangea, Spring flowers Jul-August 2 Hydrangea - Summer flowers Nov-Feb 1 Hypericum, St. Johnswort Jan-Mar 1 Indian Hawthorn (Raphiolepis) May-Jul 2 Jasmine, Winter Apr-Jul 2 Juniper Nov-Jul 0 Kerria Jun-Jul 2 Leucothoe Jun-Jul 0 Lilac Jun-Jul 2 Mahonia / Oregon grape May-Jul 2 Mockorange Jun-Jul 2 Mountain laurel (Kalmia) Jun-Jul 2 Nandina Jan-Mar 1 Osmanthus Nov-Jun 1 Photinia Nov-Jul 0 Pieris May-Jul 2 Pine (the few sheared ones) Apr-Jun 3 Pittosporum Feb-May 0 Privet (Ligustrum) Nov-Jul 0 Potentilla Oct-Mar 1 Pyracantha Jun-Jul 2 Quince Apr-Jul 2 Rhododendron Jun-Jul 2 Rose Feb-Mar
Jul-Aug1 Serviceberry Apr-Jun 0 Smoke Tree Nov-Feb 1 Spirea - Spring flowers May-Jun 2 Spirea - Summer flowers Jan-Feb 1 Sumac Aug-Mar 1 Viburnum May-Jul 2 Weigela May-Jul 2 Willow - Pussy Apr-Jul 2 Witchhazel Apr-Jul 2 Yew Nov-Jul 0 Here are some other ideas to consider about scheduling:
1. Saving removals for training – One of the best resources for practicing pruning are trees and shrubs that will be removed. Do you know someone who wants to learn how to prune? A master gardener, college instructor with a class, a friend or even yourself? See if postponing your removal will enable someone to practice pruning skills.
2. Pruning apple earlier can improve dormant spray coverage – If we wait until January or March to prune fruit plants like apple, we will have less effective dormant spray coverage. When apple are pruned earlier, such as mid-November and December, we gain better spray coverage afterward without sprouts in the way. This means using less chemical product.
3. Make sure that brittle or weak species are thinned before Autumn and Winter storms arrive. Hardwoods that are notorious for having weakness are redbud, flowering plum, sweet gum and some Robinia (locust) varieties. There are more, but those are a few.
4. Save conifer foliage that is useful for crafts or holiday decorations. If you have foliage that can be used for crafts or holiday decorations, consider postponing pruning for those plants until the holiday season has arrived. There are various types of cedar used for crafts, but conifers like blue junipers and blue spruce may also be useful for swags and centerpieces.
5. Consider your hauling capability – If you have a chipper or trailer, your debris removal ability may be almost unlimited. But if your hauling source is a large debris can that is dumped weekly, you may want to plan your pruning to get the most efficient use from your hauling service while simultaneously achieving your pruning needs.
6. Pruning to install an under-story planting: many landscape plantings – initially – can't have an under-story planting under conifers without lifting the immature canopy into a poodle. When the conifer gets larger, low limbs can be removed for space to add plants underneath, but summer heat makes that season impractical to establish new plants underneath. Autumn and winter is a good time to remove lower limbs and plant an under-story while the weather is moist and cool during a major root growth portion of the year.
7. Pruning for more light – Houses can become darker in the Autumn and winter, especially if branches block light near windows. Yearly growth can dim the interior of a house more each year. Fall is a good time to perform pruning that brings more light indoors for two seasons, at least.
8. Don't prune parts of the plant that will remove next year's color – Forsythia and Lilac, for example, form flowers next year on what was the new growth last summer. Don't do much pruning on these kinds of plants in the cool season.
9. Winter removal can reduce sunburn damage. One way plantss are harmed is by sunburn. This can happen (especially summer) by removing a lot of limbs, or entire plants, that expose large areas of bark to the hot sun. If you have big hardwoods or softwoods to remove, or large limbs that could open the exposure of sun to another adjacent trunk, then the cool season is the best time to do this. Cool season removal allows the bark of remaining plants to acclimate to the light and heat as spring weather progresses from cool to hot.
10. Manage your evergreen foliage – this can include renovation of large shrubs. Suppose you have a large laurel that you want to “stub back” rather than remove. If you cut away the limbs with foliage in November, the lack of growth in winter will provide you with about 6 months (one half of a year) of bare sticks to look at during the cool seasons. If this same large laurel was not causing significant problems, it's renovation could be postponed until near March. That would provide winter foliage and enable spring pruning that allows the plant to recover with foliage to avoid warm season sunburn damage to the bark and tissue.
11. Determine the greater need – Suppose it's better to shear an arborvitae hedge before October arrives. Then it may be wise to postpone shearing until next spring or summer. But suppose an arborvitae hedge is loaded with floppy growth and limbs. If left in that condition, rain, snow and wind could damage that hedge; causing the removal of broken and disfigured limbs that would open big gaps in the canopy. The same hedge, if left alone during the cool season, may even split apart and have the bark torn. A hedge like this with loose floppy foliage, should be sheared enough to reduce excess bulk that would cause harm if otherwise left to remain. This late foliage removal is a higher priority that adhering to a late summer shearing. It's your choice.
These are just a few examples to show the potential need to schedule pruning around the home. A few people may not need to schedule pruning due to their skill and their habits; and maybe their equipment. But many people will benefit from jotting pruning related notes on their calendar, planning notebook or computerized reminder program. We don't “have to” do it. But we should think about it.
For years the professional strategy was to paint the cuts. Then researchers found out that although the wounds had been closing faster with the paint, rot still penetrated to greater depths than if pruning people had not used any tree paint at all. So, don't paint pruning cut wounds. Big plants make their own internal would dressing. And to help the process, it is critical that the collar around where a branch meets a trunk, is not damaged.
This is not new news. Apparently back near the 1700's, some foresters were lazy and did not make cuts flush. They made cuts a little further from the trunk where the diameter of the cut was a little less. Years later, the trunk wood prepared by the “lazy” foresters was harvested. It was of better quality. That knowledge got buried over the centuries, but has resurfaced again.
Some images courtesy of the US Forest Service