Pruning Ornamental Trees, Shrubs, and Vines

8/8/2019 Pruning Ornamental Trees, Shrubs, and Vines

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Division o Agricultural Sciences and Natural Resources Oklahoma State University

Proper pruning enhances the beauty o almost any land-scape tree and shrub and is an essential maintenance practicein home landscaping. On the other hand, improper pruning candestroy the natural beauty o a tree or shrub and reduce itslandscape potential by weakening and thus disposing plantsto various maladies.

Pruning, like any other skill, requires knowledge andpractice to achieve success. Remember that pruning is theremoval o certain plant parts that are no longer e ective oro use to the plant. It is done to redirect additional energy orthe development o the owers, ruits, oliage, and limbs thatremain. Pruning essentially involves removing plant parts toimprove health, landscape e ect, or value o the plant. Oncethe objectives are determined and a ew basic principles areunderstood, pruning is simply a matter o common sense.Pruning is not di fcult i you understand the basics, taking thetime to learn why, when, and how to prune.

The necessity or pruning can be reduced or eliminatedby selecting the proper plant or the location. Plants that mightgrow too large or the site will require pruning to keep themin bounds, destroying the original intent and also making theplants unsightly and possibly weak with age. I this is the case,consider replacing the plant with a smaller growing tree orshrub such as a dwar (shorter) or astigiate or columnar (morenarrow in width) cultivar o the original species. Unless pruningis done to orm a hedge, espalier, or topiary, it should not beutilized to destroy or alter the natural plant shape.

Reasons/Bene tsPruning may be necessary to maintain a vigorous tree or

shrub. Specifcally, pruning is practiced to: Train the plant Pruning can minimize the hazard o

limbs inter ering with power lines or growing over structures.It can also remove weak crotches be ore limbs break instrong winds or ice storms and can open blocked sightlines caused by overhanging limbs at driveways or streetcorners, thus preventing injury or property damage. Asalready alluded to, pruning and shearing can also be usedto shape plants as hedges, espaliers, or topiaries.

Maintain plant health Removing undesirable growth canoster plant vigor through the removal o weak, overcrowded

limbs. Such thinning o ten improves the visual balanceor symmetry o the plant. Removing dead, diseased, orbroken branches will also aid in maintaining the shape,vigor, and health o the plant.

Improve the quality o fowers, ruit, oliage and stems Removal o the current years, aded owers and ruitclusters will promote ower buds or the ollowing season.

Why Prune? Improve and maintain plant health Improve owering and ruiting Remove dead, diseased, broken wood Remove crossing or rubbing branches Control natural shape and size

Sa ety Visibility Provide or sun and air circulation Restore balance/symmetry Rejuvenate deciduous shrubs

Proper pruning can restore a youth ul, natural growth habitin certain overgrown shrubs.

Restrict growth Regular pruning can prevent a plantrom overgrowing its space in the landscape and eliminates

the need or drastic cutting (butchery) in the uture.

Tools and MaterialsFigure 1 shows all the tools the homeowner will need orproper pruning. I a power saw is needed, hire a pro essionalarborist who is insured against personal injury and propertydamage. One should not climb trees with pruning tools unlessexperienced or when a proper sa ety harness is used. Whenclimbing a ladder to reach limbs, have someone hold the ladderor tie it in place be ore beginning to work.

Store equipment in a dry room; keep it sharp and in goodoperating condition. When pruning diseased plants, disin ectall shears and saw blades a ter each cut to prevent spreadingthe disease to healthy plants. Dip the tools in rubbing alcoholor a solution consisting o one part bleach to nine parts water.An example o this is pruning fre blight rom pears, pyracantha,or crabapples. At the end o the day, oil the pruning equipment

well to avoid rust.

Care o ToolsClean and oil tools regularly, including wiping an oily

cloth on blades and other metal sur aces. Keep cutting edgessharp; several passes with a good oilstone will usually su fce.Paint, varnish or otherwise preserve wooden handles. Usetools properly. Dont twist or strain pruners or loppers. Keepthe branch to be cut as deeply in the jaws and near the pivotas possible. Dont cut wires with pruning tools.

David HillockExtension Consumer Horticulturist

Mike SchnelleExtension Ornamental Horticulturist

HLA-6409

Oklahoma Cooperative Extension Fact Sheetsare also available on our website at:

http://osu acts.okstate.edu

Pruning Ornamental Trees,Shrubs, and Vines

Oklahoma Cooperative Extension Service


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Figure 2. Always leave one-hal the length o the candleor new growth when shearing or pruning.

Figure 3. Dehorning or topping o a tree.

limbs. There ore, timing and degree o pruning must be care ullyconsidered. Cutting all the green leaves (needles) o coni erousevergreens will kill the plants.

The narrowlea evergreens can be divided into two generalclasses: needle-lea and scale-lea . The proper time and meth-ods o pruning depend on which o the classes the evergreenbelongs.

The pine tree is a good example o a needle-lea evergreen.Trees and shrubs in this class bear branches that radiate romthe trunk in whorls, like spokes rom a hub. There is a length obare trunk between the whorls. Pine, fr, spruce and true cedar(Cedrus) belong to this class.

New growth on pine trees looks like tan candles on theends o limbs in the spring. Pruning time should be limited towhile the candle is tan-colored and be ore the needles reach

ull length. Portions o a needle-lea ed evergreen tree or shrubmay be sheared at this stage o growth to thicken an open spotin the oliage. Always leave one-hal the length o the candle ornew growth when shearing or pruning (Figure 2).

Shearing this class o plants a ter the candle or new growthstage, or below the candle, may result in death or disfgure-ment because new terminal buds may not be ormed. Do notremove the top leader o this group unless you want the plantto be shorter and denser. Some evergreens such as spruceand fr o ten ail to produce a new leader resulting in a broad,awkward shape not typical o the species.

Arborvitae and junipers are good examples o the scale-lea class o coni erous evergreens, which bear their branchesirregularly, somewhat like deciduous plants. Other examplesinclude cypress, alse-cypress, China fr, incense-cedar, andyew. This class can be pruned just be ore new growth beginsin the spring and again in May, June, or July to shape or controlgrowth. This allows new growth to cover scars be ore the dor-mant season. Just cut back to a branch ork with a green shoot.Work rom underside o branches and slant the cuts upward.Make some cuts several inches deeper into the oliage massthan others to ensure a natural looking plant.

How to PruneFirst, never remove more than one-third o the branching

system o any tree or about two-thirds o a shrub or vine in anyyear. There are exceptions however, with some shrubs ableto regenerate themselves rom the root system. Dehorning ortopping o a tree is never warranted! Dehorning a tree (Figure3) substantially shortens its li e because the stubs that are le tcannot callus over and usually become in ected with heartwoodrot and borers. Regrowth a ter dehorning orms many narrow Vcrotches, which are subject to splitting during storms. Dehorningplaces such tremendous stress on a tree that most trees dieprematurely as a result.

Pruning should ollow a defnite plan. Consider the reasonor purpose be ore cutting begins. By making the pruning cutsin a certain order, the total number o cuts is reduced greatly.Begin by removing all dead, broken, diseased, or problemlimbs by cutting them at the point o origin or back to a stronglateral branch or shoot. Removing this material o ten opensthe canopy su fciently that no urther pruning is necessary.

The next step in pruning is to make any training cuts needed.By cutting back lateral branches, the tree or shrub is trainedto develop a desired shape, to fll in an open area caused bystorm or wind damage, or to keep it in bounds to ft a givenarea. To properly train a plant, always prune in observance oits natural shape or growth habit.

Employ additional corrective prunings to eliminate weak ornarrow crotches and remove the less desirable central leaderwhere double leaders occur. A ter these cuts have been made,stand back and take a look at your work. Are there any othercorrective pruning cuts necessary? I the amount o wood re-moved is considerable, urther pruning may need to be delayeda year or so. Remove water sprouts ( ast-growing shoots o tenperpendicular to stem) unless needed to fll a hole or to shadea large limb until other branches develop.

A properly pruned tree is never obvious. I it becomesnecessary to remove a large limb, do so as illustrated in Figure4. I you do not ollow these three steps, o ten even on smallerlimbs, the weight o the limb will split the limb at the hal waypoint and rip or peel the bark, leaving a gaping wound. Pruningwounds should be kept as small as possible. Study the waythe tree or shrub branches grow naturally. Some plants haveopposite branches, some alternate, and some that whorl aroundthe limb where they attach to the trunk.

Do not cut ush to the trunk, even in the absence o branchcollars. Instead, remove limbs with bulges (branch collar) ushto the bulge, not ush with the trunk. Remove limbs without theswelling almost ush with the trunk.

Both types o limbs can occur on the same tree, and sometrees have no swelling. Some have very narrow acute-angledbranching. Others have open or L-shaped branching. The widerthe angle to 90, the stronger the branch union may be with thetrunk. Branches with less than a 30 angle o attachment o tenshould be removed or cabled. Otherwise, strong winds maysplit the limb away rom the trunk. Still, there are exceptions tothis rule. Some trees such as zelkova (Zelkova spp.) typicallyhave very narrow branch angles. It there ore is important toknow the typical growth habit o the species in question.


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Pruning DOs and DONTs DO plan every cut DO prune to an outwardly acing bud DO stand back and look DONT give haircuts DONT leave stubs DONT use dull equipment DONT prune everything into one shape

Figure 5. Proper thinning o a shrub.

Figure 4. The three-cut method or removing heavylimbs.

Branch bark ridge

Collar

31

2

Be ore A ter

Prune to the outside is a typical statement on pruningpublications. This means prune so the shoots a ter growth willgrow away rom the center o the plant. Be sure to study theposition o buds on the limbs be ore you prune.

Buds become owers, leaves, or twigs. Larger buds tendto be oral. Bud position determines the angle o the limb ortwig and its direction o growth.

There ore, either remove the limbs growing toward thecenter o the plant or cut back to a larger bud pointing outward

rom the stem, toward the outside o the tree or shrub.Regardless o what you are going to prune, start at the tip

o the branches and trace downward toward the trunk or base.Growth can be diverted to smaller twigs, branches, or budswhich will change the direction o growth. Usually, more thanone bud is stimulated to grow behind a pruning cut. The larger

bud or branch will generally become dominant and determinethe shape o the plant. So cut back to vigorous shoots or buds

acing or growing in the desired direction. This process is o tenre erred to as cutting back to a lateral (branch or twig).

Splits in the main trunk o a tree require special attentionand care by a trained arborist. Because o the special equip-ment and care needed, it is best to leave this kind o repair to apro essional arborist. Incidentally, properly trained trees seldomneed cabling or bracing at maturity.

Pruning ShrubsMost shrubs do better i pruned a little every year rather

than waiting until major pruning is necessary. Drastic pruningruins the appearance and owering or ruiting ability o some

plants or several years. It is best to cut o a portion up toone-third o the old stems at ground level and then removea portion (one-third to one-hal ) o the remaining top growth.Dense twigs and leaves make insect and disease control moredi fcult. Less annual pruning is generally required or evergreenshrubs than deciduous shrubs.

Pruning recommendations or most deciduous shrubsconsist o thinning out, gradual renewal, and rejuvenationpruning. In thinning out, a branch or twig is cut o at its poino origin rom either the parent stem or ground level (Figure5). This pruning method results in a more open plant; it doesnot stimulate excessive new growth, but it does allow room

or growth o side branches. Considerable growth can be cuto without changing the plants natural appearance or growthhabit. Plants can be maintained at a given height and width

or years by thinning out. This method is best done with handpruning shears, loppers, or a saw, but not with hedge shears.Thin out the oldest and tallest stems frst.

In gradual renewal pruning, a ew o the oldest and tallestbranches are removed at or slightly above ground level on anannual basis (Figure 6). Some thinning may be necessary toshorten long branches or maintain a symmetrical shape. Torejuvenate an old, overgrown shrub, remove one-third o theoldest, tallest branches at or slightly above ground level be orenew growth starts. When old shrubs have not been properlypruned, most o the top growth o ten comes rom two or threeold stems. This makes it di fcult to cut the old stems clear tothe ground without cutting o all the new growth. When this isthe case, make cuts ar enough above ground to leave somenew growth.

New bare-root shrubs, such as those purchased with theirroots in paper or plastic bags, should not be pruned at planting.Container-grown or balled and burlapped shrubs require littlepruning as well at planting.

Evergreen shrubs are pruned like deciduous shrubs tocontrol and shape their natural orm. But less pruning is requiredsince they are slower growing and provide a year-round e ect.Long seasonal shoots growing above the main shrub bodymay be cut back or removed entirely at any time. Narrow-leaevergreen shrubs like junipers should be pruned to maintaintheir grace ul orm and not sheared (Figure 7).

Pruning HedgesHedges are a row o plants that merge into a solid linear

mass. They have served gardeners or centuries as screens,ences, walls, and edging.

A well-shaped hedge is no accident. It must be trainedrom the beginning. Establishing a deciduous hedge begins

with selection o nursery stock. Choose young trees or shrubs


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First year- A. Large old bush. B. Remove 1/3 o old branches at ground level. C. Growth at end o frst season.

Second year- D. Use thinning technique to remove 1/3 o old branches and to cut back new growth.E. Growth at end o second season.

Third year- F. Use thinning technique to remove remaining old branches adn to cut back new growth.G. Growth at end o third season (rejuvenated shrub).

Figure 6.

one to two eet high, pre erably multiple-stemmed. When plant-ing, cut the plants back to six or eight inches; this induces lowbranching. Late in the frst season or be ore bud-break in thenext season, prune o hal o the new growth. The ollowingyear, again trim o hal .

In the third year, start shaping. Trim to the desired shapebe ore the hedge grows to its desired size. Never allow plantsto grow untrimmed to the fnal height be ore shearing; by thattime, it is too late to get maximum branching at the base. Donot allow lower branches to be shaded out. A ter the hedge has

reached the desired dimensions, trim closely in order to keepthe hedge within chosen bounds.Evergreen nursery stock or hedging need not be as

small as deciduous material and should not be cut back whenplanted. Trim lightly a ter a year or two. Start shaping as theindividual plants merge into a continuous hedge. Do not trimtoo closely because many needle-bearing evergreens do noteasily generate new growth rom old wood.

Hedges are o ten shaped with at tops and vertical sides;however, this unnatural shape is seldom success ul. As ar asthe plant is concerned, the best shape is a natural orm, with arounded or slightly pointed top, with the sides slightly taperingto orm a wide base (Figure 8).

A ter plants have been initially pruned to include low branch-ing, maintain by trimming the top narrower than the bottom sothat sunlight can reach all o the plant leaves.

These questions o ten arise: How o ten should a hedgebe trimmed? When should it be trimmed? Answers to thesecommon questions depend to some extent on how ormal anappearance is desired. In general, trim be ore the new growthexceeds one oot. Hedges o slow-growing plants such asboxwood need to be trimmed sooner. Excessive untrimmedgrowth will kill lower leaves and will also pull the hedge out o

shape. Trimming requency depends on the kind o shrub, theseason, and desired ormal appearance.What can be done with a large, overgrown, bare-bottomed

and misshapen hedge? I it is deciduous, the answer is airlysimple. In spring be ore leaves appear, prune to one oot belowdesired height. Then care ully trim or the next ew years to giveit the desired shape and ullness. Occasionally, hedge plantsmay have declined too much to recover rom this treatment,making it necessary to replace them.

Rejuvenating evergreen hedges is more di fcult. As a rule,evergreens cannot tolerate the severe pruning described above.Arborvitae and yew may be exceptions under certain circum-stances. Other evergreen hedges may have to be replaced.


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Myths About PruningThere are a number o myths and misconceptions about pruning that should be laid to rest.

Pruning is di cult. Pruning is straight orward i one knows a little about how the plant grows and what it should looklike when the process is complete. Plants will die i pruned at the wrong time o year. Plants may be injured on occasion, but seldom, i ever, are they

killed by poorly timed pruning. All pruning must be done during the winter. Actually, many plants are best pruned during the growing season. Topping shade trees will keep the trees rom causing damage to the home. Shoots that grow a ter topping are

weaker than the original limbs. They will be more likely to split o and cause damage unless they are removed everyew years. Also, wood rots are more likely to be a problem in topped trees, resulting in poorer tree health and greater

likelihood o limb breakage. Removing a tree is a crime against nature. I a plant is in the wrong place, rom a unctional or aesthetic viewpoint,

it is by defnition a weed and can be removed. This is especially true when a tree must be mutilated to eliminate theproblem it is causing.

Most trees need pruning. Actually, mature trees seldom do. Young trees usually beneft because pruning helps toestablish the basic branch structure.

Hedge shears are all you need to prune shrubs. Hedge shears are intended to prune hedges only . Using them on

shrubs not intended as hedge plants destroys the natural grade and beauty o the plants. Anyone with a pickup truck and a chain saw is a quali ed pruner. Oklahoma has no licensure or tree pruners; thussome individuals doing pruning work may not be knowledgeable or skilled in proper techniques. Never hire someonewho stops and tells you that your plants need pruning and that he or she will do it right away. Obtain re erences andsee their work frst!

All cut sur aces must be treated with pruning paint. While long recommended, research-based evidence largelysupports the discontinuance o pruning paint. Pruning paint may, in act, slow down the recovery process.

Figure 7. Proper growth o junipers (top); improperlysheared junipers (bottom).

Figure 8. Proper prunning o shrubs.

Proper prunning Improper prunning

Tools or trimming hedgesWhat tools should be used to trim hedges? The traditional

pair o scissor-action hedge shears is still the best all-aroundtool. It cuts much better and closer than electric trimmers, whicho ten break and tear twigs. Hand shears can be used on anytype o hedge, while electric trimmers do poorly on large-lea edand wiry-twigged varieties, sometimes jamming on thick twigs.Hand shears are also quieter, sa er, and less likely to gougethe hedge or harm the operator.

Hand pruners are use ul in removing a ew stray branchesand are essential i an in ormal look is desired. Large, individualbranches can be removed with loppers or a pruning saw. Chainsaws are not recommended or use on hedges.


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Pruning Ornamental Trees, Shrubs, and Vines