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4P1/9e:3 Training and Pruning

Apple and Pear Trees

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PNW 156 Revised March 1983A Pacific Northwest Extension Publication

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Contents

Basic Facts About Tree Response 3

Classes of Growth and FruitingHabit ............................................ 5

Tools for Training and Pruning ................................................... 6

Training.............................................................................. 7

OrchardDesign ...................................................................... 10PruningYoungTrees................................................................ 11PruningMature Trees .............................................................. 14Summer Training and Pruning .................................................... 19

Prepared by Robert L. Stebbins, Extension horticulture specialist, OregonState University, in consultation with Extension horticulturists at Washing-ton State University and the University of Idaho.

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Training and Pruning Apple and Pear Trees

This publication describes the most importantconcepts in training and pruning of apple andpear trees. It is intended to help the pruner whoalready has some experience to improve pruningskills. Judgments about the kind and number ofcuts to make in any particular tree should bebased on its current condition relative to thedesired objectives. This publication provides in-formation about the advantages and disadvan-tages of various training and pruning systems andhow to accomplish certain objectives.

You should recognize that there are severalways to train and prune trees successfully, butthey require an understanding of the charac-teristics of tree growth. Pruning that ignores thesecharacteristics may result in broken trees, lowyield, excessively tall trees, and reduced fruitsize and quality.

This publication first states a few facts abouttree response (an understanding of which isbasic to all pruning), defines terms used in prun-ing, and then describes the principal systems usedfor tree training. The last section tells how toprune bearing trees and contains advice on solvingcertain specific problems.

Basic Facts About Tree Response

These facts about tree response apply nomatter what training and pruning system youfollow.

1. Pruning a young, non-bearing tree alwaysdelays the onset of production and reduces thequantity of fruit produced in the early years.

2. Pruning stimulates growth near the cut;however, the net effect of pruning is to reducethe overall size of the tree and the relative sizeof the pruned limb.

3. Although pruning stimulates growth pri-marily near the pruning wound, other parts ofthe tree may grow more due to improved lightdistribution.

4. Apical dominance, in which the growingshoot tip produces hormones which move towardthe earth's center, influences the number ofshoot-forming vegetative buds, the lengths ofthe shoots formed, and their angles with the limbthey emerge from.

apex (growing shoot tip)

hormonal message

4,moves downward

shoot directly belowa vigorous shoot hasa wide angle, little growth

5. The overall shape of the tree influences itsproductive efficiency through its effect on thedistribution of sunlight throughout the tree.

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Right practice

well-lighted zone issmall, full of suckers

most of tree is poorlylighted and unproductive

well-lighted zone islarge, productive

poorly lighted zone isrelatively small

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6. Cuts made flush with the limb heal quickly,but stubs left don't heal.

7. Limb spreading affects the tree in severalways.

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a. The unspread upright limb produces thelongest shoots near its apex.

b. Moderate limb spreading, 30 to 60 degreesfrom vertical, reduces the vigor of shoots nearthe apex while increasing the number of shootsformed and the length of those farther away fromthe apex.

c. Wide spreading exaggerates this differencein the position of long shoots but may reduce thetotal number of shoots formed. The degree of re-sponse varies considerably with variety. Spread-ing limbs excessively or when the tree is too youngwill require heavy pruning to remove uprightshoots.

8. Two basic kinds of cuts in training or prun-ing are heading back and thinning out. Headingmeans cutting off part of a shoot or branch.Thinning means taking out the entire branchor shoot.

4

Heading back

a. Heading stimulates branching, stiffenslimbs, or prevents fruit set on the ends of shoots.

Thinning out

b. Thinning improves light penetration, re-directs limbs, and shortens branches.

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9. Shoots that form a narrow angle with thetrunk of a young tree will become main limbswith narrow angles. Narrow crotches include bark,are weak and split easily, and are more susceptibleto cold injury. Winter ice forming in the narrowcrotches expands and may split the trunk.

Avoid narrow crotches by selecting shoots thatform wide angles with the trunk or other branches,or by artificially spreading the young shoots asthey form.

Rightstrong crotch Wrongweak crotch

10. Shoot versus spur. The term "shoot" refersto the past-season's growth in winter or a currentseason's growth in summer. A "spur" is a veryshort shoot that usually terminates in a flowerbud. A "spur system" is a cluster of "spurs" whichoriginated from a single shoot.

The following drawing defines certain termsessential to pruning.

1 _1__ I --------- I_

The terms "sucker" and "water sprout" aresometimes used interchangeably.

11. Fall or early winter pruning can increasethe susceptibility of trees to damage in a suddenfreeze within two weeks after they are pruned.

In districts with mild winters you may beginpruning as soon as the leaves fall. In the colderdistricts wait until after January 1 to reduce therisk of damage to pruned trees from extreme cold.

Both apple and pear trees benefit from skillfulannual pruning but they differ in their responseto pruning. Different varieties of pear or appleor the same variety grown on a different root-stock respond differently to pruning. To becomea masterful pruner, you must prune and carefullyobserve the results on the same trees for severalyears.

Classes of Growth and Fruiting HabitGrowth habit refers to the overall growth

pattern of the tree and includes carriage (up-right to spreading), crotch angles (narrow towide), and branching (many to sparse).

Fruiting habit refers to the overall patternof fruiting and includes fruiting on the ends oflong or short shoots, age of spurs which producemost of the crop, and production close to thetrunk or rapidly evolving toward the extremitiesof scaffold limbs.

Most apple varieties can be classified as oneof the following four types according to growthand fruiting habit.

Type I, spur types, characterized by Starkrim-son Delicious. Type I trees tend to be uprightwith narrow crotches and sparse branching. Fruit-ing occurs on numerous short spurs which are

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long lived. The zone of fruiting tends to remainclose to the trunk.

Type II, characterized by most "standard" non-spur strains of Delicious. This is a variation oftype I in which branching is more frequent andthere is a greater tendency for the fruiting zoneto move away from the trunk.

Type III, characterized by ("standard")Golden Delicious. Type III varieties tend to bespreading with wide crotches and frequentbranching. They bear on spurs and shoots whichare generally 1 to 3 years of age. The fruitingzone tends to move rapidly away from the trunkto the outside of the tree.

Type IV, the "tip bearers," characterized byRome Beauty, Granny Smith, and TydemansEarly Worcester. Type IV varieties tend to haveupright main scaffold limbs with narrow crotchesand frequent branching. They bear much of thecrop on the ends of the previous year's shoots.There is a strong tendency for the lower half ofthe shoots to be without leaves or fruit, that is,"bare" or "blind." There is a strong tendency forthe fruiting wood to move toward the extremitiesof the branches with tree spreading as a result.

° drawing by M. Lespinasse, INRA, France,used with permission.

Tools for Training and PruningProper tree training involves cutting into small

wood, with hand shears. About the third orfourth season long handled pruning shears, oftencalled "loppers," are useful in reaching the higherlimbs. Do not use power pruners, especially mow-ers, to train apple and pear trees. The cuts madeby power tools will be too numerous and oftentoo large. Frequent sharpening of pruning toolsmakes the work faster and easier.

You'll need a ladder or some kind of man-positioning machine for the work. Since ladderfalls are the most frequent and costly source ofinjury in orchards, make sure you have a goodladder, the right size for the tree, and that youknow how to set it properly. Before operating aman-positioning machine, be sure that you havebeen thoroughly instructed in its use and dailymaintenance.

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Power saws sometimes used in pruning maybe electrical, pneumatic, or hydraulic. Small gaso-line chain saws may also be used. Power shearsare either hydraulic or pneumatic. There is atendency, when using power tools, to make toomany large cuts. Do not let the tools you use in-fluence your judgment in pruning. Do not leavestubs, as they often produce unwanted shoots andprovide an entry point for wood rots.

Training

In contrast to pruning, the purpose of trainingis to direct growth into a well-designed treestructure.

Except for moderate summer heading, prun-ing for training always delays blossom bud forma-tion and reduces fruit production in the earlyyears. Most training should be done in the firsttwo or three seasons when you use only a fewsmall cuts.

Height of heading at planting time.

Low heading, about 24 inches or lower, stimu-lates fewer but longer shoots.

Heading higher than 24 inches usually resultsin more but shorter shoots.

Delayed heading to remove the highest shootsproduces framework shoots with wider anglesthan a single heading cut at planting time. De-layed heading is not necessary in central-leadertrees because the leader stimulates wider anglesbelow.

Training to a central leaderUse central leader training in apple orchards

with tree spacings about 8 to 12 feet or closer inthe rows and 14 to 18 feet between rows wheretree height is confined to not more than 10 to12 feet. It is difficult to position a ladder to gainaccess to the tops of central-leader trained treesthat are more than 12 feet tall. Granny Smith, atype IV variety, is best grown on a dwarfing orsemi-dwarfing rootstock with a central-leader.

Although central-leader training has been usedin pear orchards, severe tree losses have beenexperienced when fire blight struck the leaderand ran straight down. Use three or four leaders inpears to protect from this danger. The centralleader system is not convenient with Bartlett orBosc pears because young trees of these varietieslack the required structural strength. Centralleader training assures development of a conictree shape that uses sunlight efficiently. Thelimited tree height and spread with this systemmakes it ideal for semi-intensive plantings.

Because of a tendency for strong apical domi-nance, it is easy to train pear and apple trees to acentral leader, provided certain rules are followed.

First, establish the dominant position of thecentral leader by removing or spreading com-peting shoots and heading the central leader.Maintain the dominance of the central leader bylightly pruning in early summer. This results ingreater net growth of young trees than moresevere dormant season pruning.

There is much variation among varieties inthe tendency to branch and to form wide crotch

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Training to A Central Leader

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angles naturally. Varieties with narrow anglesand sparse branching require removal of shootswhich compete with the leader two or more timesduring the first growing season, while a singlesummer training will suffice for others.

The central leader makes spreading of youngscaffold branches much easier since there is alwaysthe one central shoot to support the spreader.Spread scaffold branches about 60 degrees fromvertical just before pruning so that you can easilysee what pruning is needed. Thin the ends ofscaffold branches to a single shoot. Head onlythose shoots where branching or stiffening isdesired to an outside bud, removing about one-third of the shoot. Heading reduces flower budformation.

If the upper portions of the central leaderare allowed to fruit in the early years, the treewill easily bend out of shape and will not makea satisfactory amount of growth. Do not allowfruiting on one year old wood.

Solve the fruiting problem by removing thefruit or by supplying artificial support for thecentral leader. Choose whichever method is eco-nomically better for you.

It is difficult to develop a well-balanced cen-tral leadered tree on a windy site. Using an arti-ficial support to hold the tree into the wind mayenable development of the tree without excessivepruning.

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Tie the trunk and as the tree grows largertie some limbs into the wind. Supplement thiseffort by pruning to buds that are pointing intothe wind.

Training to a modified leaderThe idea of this system is to develop a strong

basic tree structure by starting with central-leadertraining but finishing with a multiple-leadered tree.A temporary central leader helps obtain wide-angled crotches both by the hormonal influenceand by affording a place to insert spreaders. Itfacilitates the selection of main scaffold limbs

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spaced about a foot apart on the trunk, whichalso contributes to tree strength.

The modified leader system is used primarilyfor apple trees whose ultimate height will be 14feet or taller with an equal or greater spread.This system has not been popularized in pear-growing districts.

Tree trained to a modified leader (at a)spreaders help to obtain a strong framework.

Training to multiple leadersMultiple-leader training is best for large apple

trees and pear trees where central leader trainingis not desired because of fire blight or tree size.

Training to Multiple Leaders

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Year 1

Use either central or multiple-leader training forapple varieties with any of the four growth habitsdescribed earlier.

Select three to six primary scaffold limbsaround the trunk and head as required to stimu-late branching. They should branch about twofeet out from the trunk. Space these 8 to 12 inchesapart vertically. Head the leaders in the dormantseason to cause branching. Do not head secondarybranches.

Multiple-leadered spur-type apple trees mayhave seven to nine scaffold limbs which permitthe renewal of fruitin.g wood by removing entirescaffold limbs. Use three or four main scaffoldlimbs for pear trees: select limbs with strongcrotches and spread these against one another,or tie the limbs out with strings fastened to clipsin the ground. Thin out the ends of the scaffoldlimbs to a single shoot and head it lightly. Theweight of fruit will further spread the tree.

The main purpose of limb spreading in amultiple-leadered tree is to obtain strong crotchangles. Excessive spreading will open the centerof the tree too much, stimulate unwanted insidegrowth, and make it difficult to maintain an over-all conical tree shape. Good light penetration de-pends on conical shape more than openess ofcenter. Avoid equal sized limbs in secondary scaf-folds as they will interfere with the dominance ofthe leader. The leader should terminate in a singleupright shoot.

If a young tree is neglected in the first fewseasons, it will require severe pruning to correcta weak framework. If there are so many scaffoldlimbs in one place that none can develop vigoroussecondary limbs close to the trunk, remove some

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by sawing them off flush with the trunk. Do notleave a stub. Remove only one or two big limbsper year.

How growth type affects trainingWhile it is possible to train every variety

without deviating from a single system, you canobtain better results with greater ease by allow-ing for growth types. In central leader training,leave more secondary scaffolds on the sparsely-branched type I (spur-types) and type II thanon the more freely-branching types III and IV.

The number of primary scaffold limbs in mul-tiple leader training should follow a similar pat-tern with seven to nine for type I, four to six fortype II, and fewer for types III and IV. This al-lows the spur types (I) to spread more, but limitsthe spreading of types III (Golden Delicious)and IV (Rome, etc.).

The "tip bearers," which tend to have longportions of shoots without leaves or spurs (typeIV), include Rome Beauty, Granny Smith, Tyde-mans, and others. These need frequent heading tostimulate branching and minimize the blind wood.Unless the tree is on a flower-promoting rootstocksuch as M 106 or M 26, heading will greatly delaythe onset of production.

The four principal pear varieties grown in theNorthwest can be separated into two groups ac-cording to the strength of their wood (tendencyto droop or weep under the weight of leaves andfruit), the age at which the tree generally beginsto bear, and by their tendency to fruit on the endsof shoots rather than setting on spurs exclusively.

Anjou and Cornice have strong wood and sel-dom bear fruit on the ends of shoots; Bartlett andBose have weak, flexible wood. Frequently Bartlettsets fruit terminally on shoots. Anjou and Corniceusually require several more years before theybegin to bear than Bartlett or Bose. Spreadinglimbs of Cornice and Anjou hastens the onset ofproduction. When artificially spread limbs of Bart-lett and Bose bear fruit they are weighted downbelow horizontal; the terminal stops growing andforms unwanted suckers. Spread Cornice and An-jou. Head long shoots of Bartlett and Bose, but becareful not to do too much spreading. Extensivespreading followed by heading of shoots fonnedin response to spreading has greatly hastened theonset of commercial production of Anjou pears.

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Intensity of spreading and heading requiredrelative to growth habit.

Number Charac- TreatmentGrowth of main teristic Spread- Head-

type scaffolds variety ing ing

I 7-9 Starkrimson much littleII 4-5 Delicious moderate mod-

non-spur erateIII 4 Golden little little

DeliciousIV 3-4 Rome Beauty moderate much

Orchard Design

Tree 16 feet tall, 30 feet wide

If trees are much wider than they are tall,the limbs will not support the crop without props,straps, or ties. The limbs will be nearly horizontaland will be prone to suckering. Heavy growth ontops of low, wide trees limits light penetration tolower limbs. Fruit on shaded limbs is small andpoorly colored. The limbs become weak and maydie.

Tree 16 feet tall, 15 feet wide

To avoid these problems, space trees aboutas far apart as their final height will be, keep theprimary scaffolds fairly upright and the secondaryscaffolds short with more spreading. Trees inhedgerows may be taller than they are wide.

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Maintain ladder bays between the scaffoldsystems for more convenience in picking and prun-ing. With large trees ladder bays also facilitatespraying.

Ladder hole

Pruning Young Trees

Finish training for basic tree shape by thefifth season. Prune young trees to control treeheight, to improve fruit quality by reducing limbrub, and to prevent excessive spreading of limbsunder the weight of fruit.

In young trees, the equilibrium between fruit-ing arid growth is easily tipped in the directionof growth by too much pruning. Too much vigorgives excessive growth and small crops of largefruit are subject to bitter pit or cork. Obtaingreater production through light pruning com-bined with strapping, wiring, or propping to keepthe fruit from breaking limbs rather than byheavier pruning to further increase limb strength.(The extensive heading used in the spreading-and-head system for young Anjou pear trees is anexception.)

Also remember that pear trees stimulated torapid growth by pruning are more susceptible tofire blight.

Make relatively few cuts on the tree, remov-ing one-year shoots if the tree is growing morethan is desired or if there are few flower buds dueto a heavy crop the previous season or to freezedamage. Any corrective pruning required onyoung trees, such as removal of excess limbs,balancing leaning trees, or reduction of height,should be done gradually over several seasons tominimize the stimulatory effect.

Fruiting habit effects on applesType I, the spur-type. Since spurs are long-

lived, it is not necessary to prune this type asmuch to renew fruiting wood as it is with treeswith other growth habits. If the tree is growingvigorously, accomplish renewal with a few largecuts to remove whole limbs back to six or seven

year old wood. Usually a vigorous shoot formsnear the cut, which if left alone, will serve as areplacement limb. Accomplish renewal with afew cuts low on the tree. On trees with "deadbud" disorder or spur-type trees which lack vigor,extensive heading is needed to maintain tree vigorand to renew spurs.

Type II, "non-spur" Delicious. More cuts intoyounger wood are required to force spurs andside branches in Type II trees. Make well-dis-tributed lopper cuts to remove limbs which have5 or 6 year old spur systems. Always cut at abranch point in order to avoid leaving a stub.

Type III, Golden Delicious. More frequentcutting further from the trunk is required to keepa majority of spurs in the 1 to 3 year old class.Selectively remove the downward hanging, olderfruiting wood.

Type IV. A relatively large number of smallcuts made far from the trunk is necessary to keepa high percentage of fruit spurs in the 1 to 3 yearold class. Cut to an upright shoot where thebranch arches.

Fruiting habit effects on pearsBartlett and Bosc. Thin out the previous

season's shoots and leave the remaining shootsunheaded except those which are so long that theywould be distorted by wind or fruiting. Headingall shoots reduces both yield and fruit size.

Anjou and Cornice. Fruit set usually limits pro-duction more than the quantity of bloom. Do nothead shoots formed the previous season. Eitherleave the entire shoot uncut or remove it com-pletely. Head at a flower bud in 2 or 3 year oldwood.

1-year shoot of Anjou pearleaveunheaded

terminal flowerbud of Anjourarely sets fruit

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Second dormant season

left unheaded flower buds form

Strong scaffolds and a cone-shaped tree aredeveloped without bench cutting.

3 year 07

1 year/year

stimulate fruit set, head to

-.: flower buds

a flower bud\

Third dormant season

___- Cut made previous season

3-year old wood2-year old bud base

_P bourse which supported a pear theprevious season

Vegetative bud

Enlarged drawing showing fruit spurs

"Bench cutting" leads to weak limbs and anumbrella-shaped tree.

Bench cut

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Once the young tree has reached the desiredmaximum height, establish a renewal point onthe leader by thinning to an upright shoot eachyear. Head the shoot to keep it stiff and uprightand to prevent distortion by wind.

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Right practice

Occasional bench cutting is useful in direct-minor secondary and tertiary scaffold limbs.

Apical dominance helps control suckering intree tops.

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- Suckers

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Wrong practice

Terminal cut to outside wood suckers pro-fusely.

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//

Spurs.

Terminal cut to upright wood forms fruit spursand few suckers.

Central leader treesThe central leader pruning system is a con-

tinuation of the training procedure, except thatspreading is no longer needed. Horizontalbranches may need to be tied up, however. Re-move all upright shoots on upper sides of scaffoldlimbs. Thin the ends of scaffolds and the centralleader to a single shoot. Remove or thin out weakspur systems.

This shows the fifth dormant pruning of a well-trained central leadered tree. Do a minimum

amount of pruning on trees of this age. Removevertical-suckers on the upper side of scaffold limbsevery year. Unless the top portions of the treeare suppressed by pruning, they will overgrow,shade out, and weaken the lower limbs. Removeextra limbs which have been left in the tree toincrease early-year cropping before such limbsbegin to crowd.

Multiple-leader treesFirst prune out limbs extending into the lad-

der bays, then start the detailed pruning from aposition in the top of the tree high enough tolook down on the whole scaffold system. If thetree is too tall to do this, either get a taller ladderor cut out the tree top. Always cut to a lowerlimb to the point where it can be reached easilyfor pruning. Remove or cut back horizontal ordownward hanging branches in the upper-outerportions of the tree. Thin the shoots around theends of all main and secondary scaffold limbs to asingle upright shoot.

Do not leave forks on branch ends. This willencourage spur and shoot development furtherback on the branch by increasing light penetra-tion; discourage excessiv. spreading by removingthe weight from ends of branches; and preventdevelopment of excess unwanted shoots throughmaintenance of apical dominance.

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Move downward through the tree, pruningmore lightly as you go. Give preference to re-moving the thinner spurs underneath limbs. Re-new old spur systems by cutting them part wayor by knocking them off to favor newly formedspurs. Keep replacement leaders coming on thesides of scaffold limbs and cut back to them asthe outer portions become too horizontal ordrooping. Thin out shoots to desired spacing andlightly head the longer ones.

Pruning Mature Trees

Mature trees require more pruning than youngtrees. In addition to maintenance of height andspread, it is necessary to maintain ladder bays.

In a well-pruned tree, the shoot growth isevenly distributed through the bearing limbs frombottom to top. Most spur systems have some newshoot growth. Maintain even growth by makingmany cuts into thin wood throughout the tree.There are few suckers to remove because cuts areevenly distributed and apical dominance ismaintained.

14

Renew fruiting wood in the same manner asdescribed for young trees.

Trees that have not been pruned for severalyears are overgrown and bushy. Restore the bal-ance of vigor and fruitfulness in trees by makingmany thinning cuts throughout the tree withemphasis on the upper, outer portions. Cut intowood that is several years old at an upward grow-ing branch or shoot. Do this for several years.Remove no more than one or two large limbs peryear. Too much pruning at one time may causethe tree to stop producing.

Excessive suckering may be due to loss ofapical dominance on nearly horizontal limbs,excessive pruning and/or excessive use of fer-tilizer. Suckers or "water sprouts" may be removedin summer.

The "umbrella-shaped tree" is the result offailure to cut into older wood and always pruningto outside wood. New growth consists primarily ofsuckers in the tree top. Lower limbs are weak andshaded. There is little new growth in the weak,devitalized spur systems. Much time and effortis expended annually in the removal of suckersand in placement of props.

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Dominant top

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'Weak lower limbs

Wrong practice

A common mistake made with central leadertrees in close planting is to allow the top to be-come too dominant. This reduces growth of lowerscaffolds and shading occurs.

ued top

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igorated lower limbs

Right practice

Constantly subdue the top of central leadertrees by pruning.

Pruning limb ends to more upright shootshelps maintain a good equilibrium of fruiting!shoot growth. If the tree were pruned to hori-zontal or hanging branches, apical dominancewould be lost, the equilibrium would be shiftedtoward shoot growth, and the tree would producemany suckers.

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The pruning of "umbrella-shaped trees" canbe reversed gradually if they are not too old.Yield will decline temporarily during the con-version.

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Controlling suckering in mature trees

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First year. A typical "sucker crown" found onthe upper side of the highest branches of a maturetree.

a. Leave a vigorous vertical sucker in thecenter; head it.

b. Leave a few weak suckers with wide angles;do not head them.

Second yeara. The vertical, headed sucker will grow vigor-

ously, suppressing growth of shoots below dueto apical dominance.

b. Unheaded weaker shoots will set flowerbuds.

Third yeara. The central, vertical sucker is renewed in

its dominant position each year by cutting to aupright shoot.

b. The weak, unheaded suckers bend underthe weight of fruit and form spur systems.

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The weak, pendulant spur systems of "um-brella trees" have little new shoot growth.

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Removal of the lowest hanging spurs andthinning the others stimulates shoot growth nearthe spurs.

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Second year

Mechanical topping and hedging is sometimesused in an attempt to reduce labor costs. If mis-used, it can reduce yield and fruit quality so thata serious net loss occurs even though some sav-ings were made in pruning costs. Masses of newshoots form along the plane of cutting and lower,inner wood is weakened or dies due to shading.Mechanical pruning best confines the tree to itsallotted height and spread before hand pruningcommences. Do not reduce the height or spreadof trees with mechanical pruning more than about2 feet in a single season. Always thin out theexcess shoots formed by the previous season'smechanical pruning. Prune by hand throughoutthe tree to stimulate growth away from the areaby topping or hedging.

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Summer Training and PruningThis bulletin has oniy discussed pruning during

the dormant season. But you can train or pruneduring the growing season to accomplish the sameor different objectives. The term "summer prun-ing" actually covers pruning at any time from thestart of shoot growth in spring until leaf fall.

As with dormant season pruning, summer prun-ing is intended to accomplish certain well-definedobjectives, such as tree training, flower induction,increased fruit set, improved fruit quality, or re-striction of tree size. These objectives may be metonly under certain circumstances. Under thewrong circumstances, summer pruning may giveunexpected, undesired results such as stunting,freeze damage, or sun-burnt fruit.

Timing for summer pruningResponse to summer pruning depends not only

on the type of cut or bend made but also on itstiming. Pruning during or just after bloom stim-ulates only slightly less regrowth than does prun-ing in the dormant season. Regrowth doesn't makeup for the growth that would have occurred with-out pruning, therefore all pruning is dwarfing.The later in the growing season the pruning isdone, the more dwarfing it is.

Pruning before the end of shoot growth almostalways results in growth of shoots from buds in theaxil of leaves in the same season. This regrowthusually is weak and spindly. Pruning after theterminals have stopped growing, generally in Au-gust, often does not stimulate regrowth the sameseason. Pruning at this time removes leaf surfacethat would have increased root growth and pro-.duced reserve starch for growth the followingseason, with the result that the dwarfing effect ofpruning is much increased. Pruning in autumn,which is not advisable where freeze damage canoccur, is less weakening than summr pruning.

Tree vigor and summer pruningTree vigor, as determined by rootstock, crop

load, variety and strain, and growing conditions, isan important determining factor in a tree's re-sponse to summer pruning. Spur-type trees, espe-daily when grown on such rootstocks as M26 or'I7a, can be badly stunted by summer pruning.frees under moisture stress or low in nutrientsnay also be undesirably stunted by summer prun-ing.

For tree trainingUsed as part of the training program, summer

bending and pruning can direct more of the tree'sgrowth into limbs that will be retained as part of

the framework and away from those that will ulti-mately be removed. When this replaces most dor-mant pruning, a large tree usually results. Startthis process in the first summer after planting. Re-move only the terminal 1 to 2 inches of the excessshoots because the leaves on the remainder of theshoot are needed to feed the growth of roots andpermanent shoots. A second tipping 45 to 60 dayslater is desirable.

Pinch temporary shoots at the same time thatclothes pins or small spreaders are installed (invarieties which require them) to develop wide-angled crotches on permanent limbs. This is whenmost shoots reach 5 to 8 inches in length. Don'thead these summer tipped shoots the followingwinter. In trees that are off to a slow start, spread-ing and pinching may stop growth entirely.

To increase flower formationOnce the tree is established and growing rap-

idly after the first season, head back unwantedshoots to the basal 2 or 3 buds that are locatedwithin an inch of the bud scale scars within 3 to5 weeks after bloom. This sometimes results information of flower spurs from those basal buds.However, if flower-promoting rootstocks and/orflower-promoting growth regulator sprays are em-ployed, summer pruning to increase bloom maynot be necessary.

To increase fruit setYoung Anjou pear trees frequently bloom well

but the fruit all abscise from the tree after reach-ing the size of a pea. Removing shoot tips beforethe fruit drops sometimes retains the fruit.

To reduce the amount of "blind wood"Certain apple varieties (Rome Beauty, Granny

Smith, and Tydeman's Red) have "blind" woodbehind the shoot terminal. That is, many of thebuds in the axils of leaves fail to grow as that por-tion of the limb enters its second season. headingshoots about 90 to 100 days after full bloom timewill allow those lateral buds to develop a littlefurther so that they may produce leaves the fol-lowing season. Remove one-third to one-half ofthe current season's growth. Do this only to vari-eties that need it because it increases susceptibil-ity to damage in an early freeze.

To restrict tree sizeSummer pruning can restrict the size of mature

trees. Make cuts into wood two years or older inlate July or early August preferably next to strong-

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growing shoots. Be careful not to expose fruit tosunburn. Summer pruning the tree tops maystrengthen flower buds below. This kind of prun-ing replaces dormant pruning in the parts of thetrees that are summer pruned, and makes the treesmore susceptible to damage in an early freeze.Pruning in mid-August or later further increasesthe risk of freeze damage. If regular summer

pruning is required to control tree size, considerthinning the orchard.

To eliminate unwanted "water sprouts"Removal of "water sprouts" or "suckers" in

June or July may reduce the amount of regrowthin comparison with dormant season pruning. Itwill reduce competition between shoots and fruitfor calcium.

Pacific Northwest cooperative Extension bulletins are joint publications of the threePacific Northwest statesOregon, Washington, and Idaho. Similar crops, climate, andtopography create a natural geographic unit that crosses state lines. Since 1949 thePNW program has published over 200 titles. Joint writing, editing, and production hasprevented duplication of effort, broadened the availability of faculty specialists, andsubstantially reduced costs for the participating states.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30,1914, by the Oregon State University Extension Service, Henry A. Wadsworth, director;Washington State Cooperative Extension, J.O. Young, director; the University of IdahoCooperative Extension Service, H.R. Guenther, director; and the U.S. Department ofAgriculture cooperating.

The three participating Extension Services offer educational programs, activities, andmaterials without regard to race, color, national origin, or sex as required by Title VI ofthe Civil Rights Act of 1964 and Title IX of the Education Amendments of 1972. TheOregon State University Extension Service, Washington State University CooperativeExtension, and the University of Idaho Cooperative Extension Service are Equal Op-portunity Employers. 50/50/50

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