THE STATE COLLEGE OF WASHINGTON PULLMAN, WASHINGTON

EXTENSION SERVICE W. S. Thornber, Director

PRUNING APPLE AND PEAR TREES

By 0. M. MORRIS - Horticulturist

The State College of Washington and United States Department of Agriculture Co-operating

March, · 1919 - Series I No. 50

Pruning Apple and Pear Trees By 0. M. MORRIS

Th~ best place to study pruning is in the most productive orchards in the community. .. Study there the system of pruning that has been practiced on the best and most satisfactory producing trees. Become acquainted with the habits of growth of the different varieties and the form of the tree at different ages. Adopt a system of tree de­ velopment that has given satisfactory results in your community in the quantity and quality of fruit produced. Systems of pruning recommended by fruit growers from different sections than yours may not be at all satisfactory in your district. A system once adopt­ ed and established should not be changed except for very good reasons. APPLE TREES The one-year-old tree just set in the orchard should be cut back to a straight stock about three feet in height. This cutting back should determine the height of the trunk. The upper buds left will usually be the ones to produce the branches that will form the framework of the head. These branches which are to form the permanent. frame­ work of the tree should be distributed through a space of 12 inches, extending downward from the top of the young whip. The branches that are only three or four inches apart on the young tree will be too close together by the time they are four or six inches in diameter. Trees with a clean trunk 20 to 24 inches high are easier to cultivate and work around than trees with a shorter trunk, and a few inches difference in the height of the trunk of the tree does not modify greatly the convenience of the work of pruning. spraying and har­ vesting the fruit crop. The extremely short trunk is not a8 popular after the trees are in full bearing as it is while the trees are two or three years of age. Trees that are growing very rapidly and producing long slender shoots can be made more stocky bv clipping off the growin~ tip of the branches during the summer. Branches on the windward side of trees exposed to strong nrevailing winds ~an sometimes be kept growing in almost normal position by careful attention to summer tipping back. Trees that are vigorous and strong will ~row in better form with little or no care, than weak trees can be developed with all the pruning and training that may be given them. The two-year-old nursery tree is seldom used in this State for planting commercial orchards. It can sometimes be used to ad- 8 vantage for home orchards and in replanting, but must be severely cut back at the time of transplanting. The three to five branches selected to form the framework are cut back to about one-third of their length and all others removed. In varieties like Jonathan, Winesap, and Ben Davis, the center or leading branch should be left several inches above the highest side branch. Cutting all branches back to three or four buds may be advisable if the trees have been exposed to drying conditions after digging, or if they are to be plnnt­ ed in a district of light rainfall without irrigation. When good treH:; are planted in a section where moisture is abundant, as in most Jis­ tricts of Western Washington, they wHl make a good growth if given only enough pruning to secure a well balanced top.

Figure I. A young Jonathan tree pruned to a central leader form. This is a good type of tree and is well pruned, altho not quite ideal, because of the low trunk.

4 The tree that has made one year 's growth in the orchard shot1l:i be carefully pruned, although this pruning should not necessarily be extremely heavy. A few years ago, when so many commercial .orchards in the Northwest were young, the practice of very severe pruning of young trees was common. It was carried to a destructive extreme in many cases. Winter pruning that cuts away three-fourths or four-fifths of the previous summer's gr owth of wood does not assure a stocky growth of trunk and permanent branches, but cam~ es the production of another crop of long, whip-like branches. It is not necessary at the first winter pruning to select the branches that fi.re to form the permanent frame of the tree and remove all others; h:It

Figure 2. A Delicious tree that has been excessively pruned. It is now carved out to the .vase form. if they can be selected, the pruning should be so done as to give them the advantage. A little thinning out of the top to let sunlight in ;md tipping back of the longest shoots is usually all that is necessary at this time. It may not ruin the tree to do more, but usually, light pruning will accomplish about all that can be accomplished by a more severe pruning. The old controversy as to the advantages of a treP with 9 central leader or one that has been developed in vase form is not discussed so much as the orchards grow older . Neither extreme form is desir· 5 able and both forms are foreign to the natural development of the tree, ~nd if the tree is given reasonable opportunity to develop this extreme soon disappears. The natural and best form is about mid· way between these extremes. The center of the tree must be open to light without regard to the particular way in which the scaffold limbs are distributed. Trees that are prone to develop low drooping side branches, as the Jonathan, can often he developed in a form of central leader type for a few years to advantage. Other varieties, as

Figure 3. A Jonathan tree excessively pruued by con­ stant cutting back and removal of small twigs, resulting i.n an over abundance of large branches about the same size. A tree of this type requires the removal of a large number of these large branches with a minimum cut­ ting of small ones. the Esopus and Rome Beauty, do not lend themselves well to this type of young tree. The vase form is purely an artificial type con­ ceived in the mind of the grower. The trees can be trained to this type, but· it is seldom a profitable form. The Second Winter Pruning . Thin out the top of the tree where the number of branches growing is so great as to cause the 1imhs that are mo;e or less permanent to 6 be very slender. Small side shoots should not be removed because of their value in helping to develop and make more stocky the main branches to which they are attached. The top should be opened by removing large limbs as far as possible ·without destroying the frame of the tree. The large limbs and trunk require protection from ex­ treme heat of the summer sun and the development of a reasonable quantity of laterals tends also to bring the tree into early fruit pro­ duction.

Figure 4. Trunk and framework of a young Jonathan tree after bearing its second crop of fruit A form "thought to be almost ideal by many grow­ ers. The trunk is too short and the branches too nearly horizontal in their direction. Such trees usually require heroic treatment later, with the re­ sulting loss of production.

Beginning · with the second winter pruning the work should be mostly corrective in its character. Prune out wo'od that ]s where none is wanted and correct faulty distribution of branches. The main business of the tree during the period of development before heavy fruit production begins is to produce wood, or to grow, and for this purpose an abtmdance of foliage and small twigs are neces­ sary. It is a wise plan to leave plenty of wood in a tree t o be taken 7 out later, but all branches that interfere with the framework should be removed. Wood once taken out can not be easily r eplaced by new growth, but excessive growth can be cut away at an y time. From the time of the second winter pruning until fruit production is established, pruning should be done with the idea of training to the adopted system more than modifying growth. Most of the work should be done in the winter, but constant attention thruout the year is necessary to have the trees make the most rapid permanent prog­ ress. The top should be open enough to let a little of the direct rays of the sun reach the ground beneath. The change from a nursery tree

Figure 5. A Jonathan tree of the same age as Figure 4 but of better form. to a tree in full fruit production is gradual without definite dates o~ sudden .changes from one stage to another. Pruning is only one of several cultural practices necessary to secure the maximum fruit pro­ duction and it can not be used successfully as a substitute for soil fertility or good tillage. If the trees are well grown in the nursery and well planted on good soil and if thereafter they receive plenty of moisture and soil tillage, they will develop into good fruit pro­ duction. 8 In pruning :5 oung trees, a great deal has been said and practiced relative to the point at which one-year-old branches should be cut. A great deal of emphasis has been placed by some pruners upon cutting the branch diagonally so that the base of the cut would be opposite a bud. If they desire to have the trees spread more they cut back to a bud pointing toward the outside of the tree. The careful cutting close to the bud avoids the dead stub that develops if a twig is cut one-half inch or more above the bud. The tip bud.

Figure 6. A common type of trunk and base of the framework of a mature fruiting Jonathan tree. left on the branch usually assumes almost the original direction of the branch and the lower branches from side buds because of their position and exposure to light assume lateral directions. It is often advisable to develop lateral spreading branches by first pruning to an inside bud and the following year cutting back to the second or­ third branch which has assumed a distinctly lateral direction. This is especially true with Rome Beauty and Wagener. - In pruning trees four years old, or older, the extra care required to "cut to a bud" is not worth while. Side branches, however, that are removed should be .cut close to the parent branch; and ter minal branches, when cut back to side branches, should be cut close so, that no stubs are left. 9 Fruiting Trees Green skin varieties may be permitted to develop a more dense top that red skin varieties; but a thick top tends to shade and kill the interior branches and twigs, and to cause the production of fruit to be carried by the branches further from the trunk. This reduces the load of fruit that can be carried by the tree and is not desirable. Red skinned varieties should have the tops of the trees kept suf­ ficiently open so that good strong sunlight can reach past the center of the tree top. This will maintain strong, even development of the fruit spurs and lateral fruiting branches, and secure the maximum coloring of the fruit. As the trees attain age, the amount of pruning done on each tree should be increased and the amount that should be done will depend upon the growth and development of each individual tree. Enough of the top .should be removed to keep it open and shapely, and in a good, vigorous growing condition without reducing its fruit produc­ tion. No definite rules can be given, but the skill of the grower will be measured by the degree of accuracy of balance b~tween his prun­ ing and other cultural operations that cause the tree to yield its maximum quantity and quality of fruit annually. Special practices in pruning such as girdling, stripping of the bark, and other mechanical injuries intended to induce fruit pro­ duction on vigorously growing trees, are extreme measures and are not to be advise& under ordinary conditions. If trees will not bear good crops of fruit without these special treatments they are not adapted to their location and should be removed.

Season "of Pruning The general practice is to do the larger part of the pruning during the winter. This has two things to justify it. The workman can have a better view of what he is accomplishing and there is then more time for the work: As a rule, tree8 pruned in winter have a stronger tendency to respond to producing ·new growth .in the form of water sprouts or new twig growth at the points where the cuts were made. Summer pruning as usually practiced by careful growers 6s as much training as pruning, and is practiced for the purpose of modi­ fying the form rather than the growth or fruit production of the tree. Heavy summer pruning may accomplish the same results that heavy winter pruning ordinarily accomplished. It may increase or decrease wood production or fruit production. Summer pruning can be practiced for the purpose of modifying the shape of ·the tree top without altering its habit of growth or fruiting. The exact dates at which summer pruning may be done for the purpose of increasing fruit production can not be indicated by the calendar with any de­ gree of exactness. Results depend upon growth conditions follow­ ing. the pruning and the kind of pruning done more than upon the date of pruning. 10 Figure 7. The fruiting branches of a Jonathan tree. Note all of the large terminal buds both on the twigs and the spurs are blossom buds for next year's crop. At the point A the fruit spur has developed into a twig. Such forms are common to this variety.

11 Late w1nter and early spring pruning is less liable to be followed by the ill results of the killing back of tissue around the edge of ·large wounds than the pruning done in late fall and early winter. The wood should not be frozen when the pruning is done, but in many of the irrigated sections pruning while the wood is frozen fre­ quently results 1n no harm to the tree.

Figure 8. A common type of trunk and lower framework of a Rome Beauty tree.

The young, rapidly growing tree constantly tempts the pruner to head back severely each year. Heading back causes the development o:E lat eral buds and branches in the immediate vicinity. It does not greatly modify growth nor strengthen the main branches or limbs of the tree. Shortening of" the longest branches is often necessary. This can be done with a minimum loss of time and energy to the tree by frequent tipping back in summer. Persistent annual heading back delays as often as it hastens fruit production. It commonly results in the formation of a tree with an excess of lar ge branches and an 12 undersupply of fruiting wood in the center of the tree top. The thin­ ning out of the top should consist 0f the removal of crossing and in­ terfering twigs and small brancht> ~ and of such larger branches as will prf>Yvnt the best development of the remaining limbs. A great aea1 of small sidewood should be left. It increases the diameter of the main limbs and causes the tree to come into fruit production at an earlier age. Thinning out by the removal of large branches is not so frequently overdone as is heading back.

Varieties The commercial varieties grown in Washington differ greatly in their general shape and characters of gr owth and each r equires more or less different lines of treatment to prune them best .

Jonathan The Jonathan tree is typical of those that are inclined to start with a strong central leader and very quickly develop strong lateral branches. The central leader usually subdivides by developing in lateral directions and the strong side branches have a tendency to assume a horizontal position and, with a heavy crop of fruit, to be­ come pendant and drooping. The extremely short trunked trees of this type are disappointing because the fruit is produced so low that it hinders the ordinary cultural processes and the fruit produced on such branches is of poor color and quality. A constant effort is necessary to keep the tref' growing in an upward direction suf­ ficiently vigorous to deve.lop and color its fruit well. Young trees should be trained to grow upward with the knowledge that heavy fruit production will cause the top to spread and as the trees grow older more severe training and more thorough fertilizing of the soil is necessary to maintain vigor in this variety. This variety has a good habit of bearing fruit on small side branches and with proper training the fruit will be well distributed from center to circum­ ference of the top. Rome Beauty Rome Beauty produces a tree that, until fruit production begins, has a strong tendency to grow upward and the branches assume a lateral direction only when trained by the grower or held in that position by a load of fruit. This variety has a strong tendency to produce its fruit on long fruit spurs which are often more like ter­ minal branches than fruit spurs of other varieties. A rather thick, bushy top is required by this variety for the production of a crop of fruit distributed throughout its top. The most common experience of the unskillful grower is to have the Rome Beauty produce a large amount of fruit in the outer part of its top. This causes a drooping of the branches and often a canopy form of top in late summer and early fall, with the result that a very large proportion of the crop 13 iS not well exposed to the sun and colors poorly. A rather severe thinning out of the large branches and careful tipping back of the ~oung shoots is necessary to secure an even distribution of fruiting wood throughout the top of this variety. It does not develop its fruit well on short side spurs, as does the Jonathan; and growers expect it normally to produce a larger proportion of its fruit in the c;mter part of the top.

Figure 9. The fruiting branches of a Rome Beauty tree. The enlargements of the branches marked by B are the points at which fruit was produced last summer. The buds marked A are blossom buds for the next spring's crop. Note the long twig growth beneath each of last season's fruit spurs.

BEN DAVIS The B-en Davis, Gano, Black Ben Davis, Arkansas, Winesap, Stay­ man Winesap, and Delicious, as young trees, have a strong tendency to grow in height with a development of well distributed lateral branches capable of making a good well-balanced top. All of these varieties can be well developed by starting the young trees with a central leader and maintaining it for three or four years. The maintenance, however. 14 of the central leader with these varieties is not as important as with the Jonathan and, as with that variety, it will usually cease to be noticeable in trees seven or eight years of age. All these ·varieties are vigorous growers as young trees and can be easily trained to open tops with well-balanced heads. The Ben Davis, Gano, Black Ben Davis, Arkansas, Stayman Winesap, and Delicious are vigorous trees even while in heavy fruit production. These varieties are moderate­ ly heavy, annual fruiters. The Arkansas Black is often a light pro­ ducer and should be pruned so as to open the top as much as possible t J

Figure 10. Base and framework of a Gano tree. This shows the type of frame­ work that is common but the individual tree has too short a trunk to be satisfact­ ory.

with the removal of a minimum amount of wood. This process will usually bring the trees into their heaviest fruit production. The Winesap is a vigorous growing tree while young; but, when heavy fruit production begins, the tendency of the tree is to over-bear and lose vigor. This must be corrected by sufficient pruning to prevent an excessive development of fruit wood and the maintenance of a good supply of young growing shoots. Pruing alone can not secure the best results with this variety; but thinning of the fruit and im- J5 provement of soil fertility and tillage must be depended upon to secure the annual production of extra fancy fruit. The Stayman Winesap js less inclined to over-bear, but in other respects is very much like the Winesap tree. Esopus The Esopus (Spitzenburg) is difficult to prune to the best form. The tendency of the tree is to produce long branches and to produce the fruit on short spurs distributed along these larger branches. Young, vigorous growing shoots that are headed back frequently fail to produce three or four side branches as desired, but produce one and sometimes two branches which assume the direction of the or­ iginal branch. Every effort posible is usually necessary to cause this variety to produce sufficient side branches to carry a good crop of fruit. The variety also has a strong tendency to biennial crop pro­ duction. Thinning the fruit and careful, regular annual pruning with good cultural care will do the most possible to overcome this unsatisfactory tendency. Wagener The Wagener tree must be treated very much the same as the Spitzenburg in as much as it fundamentally develops in the same way. Careful thinning of the fruit of this variety is necessary: to avoid biennial fr.uiting. · Another peculiar characteristic often mani­ fest is the tendency of the tree to produce a heavy crop of fruit on two or three large branches while the remaining part of the tree will have very little, if any fruit. Careful thinning and regular an­ nual pruning ~ill do the most possible to correct this habit. Yellow Newton This variety often puzzles the grower with its tendency to produce many long slender branches with a strong upward tendency of growth. Careful thinning of the largest branches with light heading back and encouragement of small side branches will produce the best results. Wounds W ounds heal by the growth of the adjacent camb.ium layer and bark which gradually spreads over the exposed area. The more rapid the growth of the plant in that area the more rapid the healing .. Stubs of branches left by pruning heal slowly because they are usu­ ally removed from the line of travel of the sap which feeds the new developing tissue. Not only the fresh cut wound that is exposed must be healed, but the entire stub should usually be considered as the area to be healed in the growing process. This makes it doubly important to prune carefully in r emoving large branches and to make the cut as close as possible and almost par allel to the main branch or trunk. 16 Figure 11. A fruiting branch or a Gano tree. Note the distribu­ tion both on long and short spurs or twigs of last· year's fruit crop produced at points B.

17 Wounds made in the process of cutting away diseased parts oi trees should always be disinfected and for this purpose there is prob­ ably nothing better than a 1 to 1000· solution of corrosive sublimate (mercuric chloride). It ·is now prepared in tablets, one of which dissolved in a pint of warm water, gives the desired solution. Hr:tft­ ing wax and similar preparations are often used on stubs left by removing branches but this material is of doubtful value. The nse of common white lead paint is growing more in favor and ~ eems under the greatest range of conditions to produce most uniformly satisfactory results. The practical value of any dressing for woun•ls lies in the extent to which it disinfects the wound without injury to the tissue, and prevents ex cessive drying.

Broken Trees Branches broken by an overload of fruit or by a storm can seldom be repaired with good results. Small branches that do not .leave large enough open spaces in the trees t o be a serious loss should be cut back to side branches or to a parent branch. The neighboring branches will, if permitt ed, soon fill such spaces. Large branches, when broken should be cut off smooth with a saw and the following ·winter top grafted. If the work is well done .the open space left will be filled in jwo pr three years by the new wood. This form of renewal can very often be quite satisfactorily used and r educes the loss from such breakage to the minimum. Large branches that are split from the trunk of mature trees can often be lifted back to their original position and fastened there with a bolt through the base. Guy wires should then be attached to the oranches higher up to help hold the load. The bolt used should have no larger head than is positively necessary to hold the weight and should be sunk into the wood. This will enable the wood to heal over quickly. Large wood screws that will not reach quite through the base of the tree can often be used with better results than bolts. This work must be done very soon after the damage has occurred. If a top is permitted to retain this broken poshion long the wound will dry badly and worse breakage will occur when the repair is att empted. If this repair work can not be done very soon, it is usually better t o remove entirely the broken parts. Young trees badly split or broken can best be renewed by .trimming away the broken parts and permitting . the trunk to de­ velop a new top. In extreme cas.es, it is best to remove the tree entirely and replant with a young tree. There are many.forms of supports used in trees to prevent break­ age. The best system is to prune and train the tree so that the large limbs will be evenly distributed and sufficiently strong to support a large crop when the fruit is properly thinned. The special prop­ ping of individual limbs will be required occasionally in heavily bearing orchards that have received the best pruning and training 18 possible to give, but proper thinning of the fruit will usually enable the grower to dispense with nearly- all props. Live ties, formed by twisting together two young shoots from op­ posite branches, have been used in a great many orchards. The ob­ jection to this is that it is sometimes a ~breeding , and ~odging place for insects and that it is not where the support is most defi­ nitely needed. It is practically impossible to use these at any other position than low down in the framework and for that reason they are unsatisfactory. It is better to avoid so far as possible, the forma­ tion of a tree that makes necessary the use of such ties.

Figure 12. A Wagener tree that has been in fruit production three or more years. Note the distribution of the fruiting spurs along the side of the long pole-like large limbs.

Cross tying opposite limbs with wire that is fastened to screw eyes placed in the limbs is sometimes used to good advantage. Usually~ -however, such ties are too rigid and do not completely avoid break~ age. The center prop system with guy wires running from the top of a pole standing in the center of the tree to each individual branch

19 is used by many with very satisfactory results. The damage that is liable to occur with this form of prop is that the point of support is placed under the limb too near the trunk, with the result that the l!imb breaks near the point of support. In order that this system ~nay be used to its best advantage, it is necessary that the pole ·stands well above the highest branches of the tree. The individual pole prop has the advantage of be­ ing susceptible to adjustment in any way that the situation may demand and can be removed easily as soon as its need has ceased to exist. All forms of props should be considered as a temporary relief from the unsatisfactory situation that has developed and no form. can be devised that will be of any more than temporary value. The growth of the tree and its development from year to year will change the position and amount of assistance needed to carry the load of fruit.

PEARS Young pear trees are pruned very much the same as young apple trees. A greater effort is usually -made to cause the young trees to assume a spreading form. A little summer pruning may be very helpful ir. accomplishing this. The top branches, if cut back to an inside bud, will throw out several branches and the following year the two-year-old branch can be cut back to the one-year-old outside branch. This process will usually secure a greater spread of frame­ work than cutting to an outside bud. Heavy cutting back is often carried to an excess in an endeavor to cause the young tree to develop more side branches and to cease its strong upward tendency. Better re­ sults will often be attained if the trees are brought to bearing age with no more pruning than is necessary to secure a good well balanced framework. After the habit of fruit bearing is well established heavy pruning is most successful. The trees, while bearing heavy crops of fruit, develop more lateral wood and assume a more spreading form. The fruit may be thinned by pruning, but hand work in removing the fruits is much more successful. The most important work in pruning is to head back the few longest and strongest growing

Figure 13. A fruiting branch of a Wagener tree show­ Ing the short fruit spurs and the tendency of the variety to produce extensional branches when headed back. 20 branches and remove enough wood to mai11tain the v.igor .of _the tree, Mature trees in heavy bearing require heavy annual pruning., _The top should be kept sufficiently open to let some of the direct rays of the sun reach well into the center.

Figure 14. An ideal form of Bartlett pear tree in full fruit produc­ tion. Note the upright form of the main branches or framework of the tree and the crooked stub form of the smaller wood.

The pear. bears its fruit from blossoms borne in winter terminal buds on spurs, and the heavy fruiting tree tends to fill the top with short crooked spur wood. This must be greatly thinned each year at the same time the strong terminal branches are cut back. By care­ fully maintaining a balanc.e. these spurs will continue a vigorous. 21 growth at the same time the outer branches are making strong wood growth. The varieties of pears differ greatly in their habits of growth and the. system of pruning followed must be especially adapted to each variety. The Bartlett and the Kieffer are very vigorous growers as young trees and all the branches grow nearly straight up. Heavy winter pruning seems to accentuate this characteristic. The older trees develop a more rounded top. The Winter N elis produces such crooked branches that all that can be done for it is to thin out the top to admit light and cut back some of the longest .and strongest growing shoots. In pears, as in apples, heavy pruning of young trees tends to delay fruit production and if not well done will do more harm than if pruning had been. neglected. The presence of diseases sometimes makes it necessary to cut away most of the fruiting spurs developing on the large branches. Th1s, however, should be practiced only as an expedient under abnormal conditions. Best production can take place only when fruiting spurs · are distributed from the center to the circumference of the tree top.

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