Tree Trimming and Pruning With a Purpose
The urge to prune is strong in spring. Like most primal impulses this may be directed into constructive or destructive channels. All too often the latter course prevails. Before you prune be sure that you know what you are doing and why.
It is almost as sensible to allow an untrained person to fix your teeth or a non-medical man to operate on your body as it is to tackle pruning without at least a rudimentary knowledge of how plants grow and what their responses to each cut are likely to be. Oh, it isn’t quite as bad as that; trees and shrubs rarely die from faulty pruning (although certain kinds may), and no pain is inflicted. But they may be seriously crippled and their ability to flower and fruit destroyed or curtailed. They may be changed from attractive entities to stylized, unlovely even ugly-specimens;
The results of good pruning are well shaped plants - whether they be in the shrub border, a hedge or tree. To achieve this - pruning must be done with a purpose. There is a reason for removing or shortening branches. Sometimes it is to prevent growth; other times to increase growth - such as in the example of hedges.
No Right Way
There is no one right way of pruning. Techniques must be varied according to the kind of plant and what you want of it. Let’s consider spring pruning from this latter point of view, always bearing in mind that what you would like may not be possible with the kind of plant you have.
When a branch is cut off completely, no further growths can come from it. But if a branch is merely shortened, in most cases it gives rise to several lateral shoots, the strong ones usually springing from near the top of the cut-back branch. Whether or not laterals develop sometimes depends upon the age of the branch at the point where the cut is made. When so many shoots grow that they are crowded and receive insufficient light they will be abnormally thin and weak and will not flower and fruit well.
Proper cutting of branches is also of importance. The correct way is shown at the left - the cut slightly above the bud. On the right are three examples of improper cutting: too close to the bud; extreme slant of the cut; and ragged cut made with hull clippers. Poor cuts will often lead to rotting of the branch tip.
From the above it is plain that when we want more shoots we shorten branches; when we want stronger shoots, more likely to flower and fruit, we cut out branches completely. Often we do both to the same plant, removing some branches so that only a reasonable number remain, and shortening others to encourage new shoots where needed. These facts you must remember when you prune with a purpose.
Purpose: to rehabilitate a deciduous shrub (one which loses its leaves in winter), unpruned for years, that flowers unsatisfactorily and is dense, spreading, overgrown tangle, crowded with dead wood and weak shoots.
Time of flowering governs to an extent the method of pruning. On the left is an example of spring blooming plants before the leaves appear. On the right is a summer blooming plant. These flower after the leaves have formed, often as branches which grew during the current season.
Prune before its leaves appear, no matter when it blooms. You may sacrifice flowers but only then can you see what you are doing and remove prunings without seriously injuring new growth. Be bold. Cut out all dead wood (it is brittle, snaps easily; if you scratch its bark no green shows underneath; buds on it do not become plump in spring as they do on live wood). Next, remove completely all very slender, weak, obviously crowded shoots.
Appraise what is left. Retain a framework of branches so spaced that after pruning you have the skeleton of a well-shaped bush with each framework branch and all shoots that will grow from them assured of plenty of light and good air circulation. The framework branches will probably not all spring directly from the ground; some will originate from other branches. It is important that they be few in number and that there is ample space between them.
An Old Spring-Blooming Plant, unpruned for many years would look something like this. There would be a mass of old and new branches crowded in the center. Examples would be forsythia, shrub roses, weigela and mock-orange.
Most may be shortened, because you get stouter new shoots from the end of a cut-back branch than from one not so treated. Each time you cut back a branch conjure a mental image of two, three or more shoots arising from the upper part of the cut-back stem, because that is what will happen. Make sure the branches are sufficiently far apart that the new growth can develop without crowding. See that the framework retains the basic natural outline of the shrub. Don’t stylize it or lose its grace.
After pruning the plant appears open and lighter. The idea of pruning here is to remove stems from deep in the plant to prevent additional stems from forming. Too many stems prevent light from entering into the plant, reducing flowering and preventing goo development of brances. Avoid “crew-cut” type pruning.
Purpose: to renew a shrub or small tree (evergreen or deciduous) that has grown tall and lanky and is, perhaps, bare at its bottom.
Summer blooming shrubs those that flower on present year’s wood can take drastic pruning. Some plants of this type can even be pruned to the ground. Examples of summer blooming shrubs are: abelia, rose of sharon, crape-myrtle
You can do this with some kinds, not others. The critical point is its ability of producing new branches from the base of the trunk or stems. Among kinds that do are rhododendrons, hollies, camellias, mountain-laurel, aucuba, boxwood, oleander, pittosporum, evergreen barberries and practically all broad-leaved evergreens, lilacs, redbud, crape-myrtle, rose of Sharon, deciduous barberries, mock-orange, privet, viburnums, tamarix, bush honeysuckle and the majority of deciduous shrubs and a few small trees but not most large trees, such as oaks, elms and maples. Most narrow-leaved evergreens, such as firs, spruces, pines and hemlocks, cannot be handled in this way; yews are a notable exception.
After pruning the framework of the plant need remains. All the second-year shoots have been removed to an inch of the major frame. Two or three new shoots will come from each cut made on second year branches. This type of pruning which increases branches will also increase the flowering.
Cut off lanky specimens a foot or less above ground level before new leaves begin to grow. Fertilize the soil and mulch it with peatmoss, compost or similar material and make sure that at no time through the summer do the cut-backs suffer from drought. By fall they will be shapely little specimens and will improve each year under reasonable care. One thing is important: eliminate whatever caused legginess in the first place. If you don’t, the new top will develop as the old. Most likely causes of legginess are shade or crowding. The removal of neighbor plants may be necessary.
Small trees need attention, too. Remove all dead wood and sucker shoots which will come either from lower branches or below soil level. Also trim off lower branches to allow head room when walking underneath. Large tree demanding climbing should be pruned and repaired by professional tree experts.
If you can’t bear to cut your specimen down so completely at one time, much the same result may be had by spreading the work over two or three years if it has a number of stems from the ground. To accomplish this, shorten half or one-third of the stems to within a foot of the ground each spring. before new growth begins. In my opinion this is less desirable than cutting all down at once.
Roses are actually summer-blooming woody plants. They flower on branches formed during the growing season. All dead branches and dead tips or branches are removed first. Weak shoots are then taken out and the firm branches quite often formed during the previous season are shortened approximately 18 inches.
Purpose: to maintain deciduous flowering shrubs that have sufficient space to develop and are not dreadfully overgrown.
A straggly Rhododendron can be rejuvenated by crastic pruning. Rododendrons as well as liliacs, hollies, boxwood and camellias have hidden buds even in older stems which will start into growth if main stem is cut. Some plants do not have these buds and cannot be treated this way.
First, consider whether they need pruning beyond removing dead wood and occasional straggly or misplaced branches. Some, such as azaleas, star magnolia, viburnums and fothergillas, don’t. Prune annually only those that become tangled if this is not done. Some kinds, such as forsythia, mock-orange and early blooming spireas may need attention every two years only.
Next, determine whether flowers are borne on the current season’s growth or older growth. In other words, will shoots that originate this spring bear flowers in June or later, or are flowers that blossom before June borne on branches developed last year or earlier?
Cut main stem to about a foot from the ground. The hidden buds will start growing and by the end of the first season, the new plant will begin to take shape. It is necessary too, to keep the plant well watered and mulched during the first two seasons to prevent the cut main shoots from drying out.
Prune shrubs that bloom on current season’s shoots before they come into leaf, those that flower on older, wood immediately after the flowers have passed. The former may be cut completely to the ground. A framework of permanent branches (or of trunk and branches) may be preserved and the stronger shoots of the previous year pruned back to about an inch of their bases, with the weaker ones removed.
Alternatively, if there is space enough, they may be allowed to grow naturally with little or no pruning. Some, such as peegee hydrangea and crape-myrtle develop into sizable treelike shrubs when left unpruned. Among kinds that flower on current season’s shoots are abelia, butterfly bush. (Buddleia Davidi varieties), spireas of the Anthony Waterer type, blue spirea (Caryopteris), rose of Sharon, peegee hydrangea, chaste tree (Vitex), lespedeza, St. Johnswort (Hypericum), Tamarix pentandm and crape-myrtle.
In several years the new Rhododendron is well developed. To prevent it from becoming straggly again, the causes for the initial poor growth must be eliminated. In a group planting of Rhododendrons, don’t cut all plants back in one year for then the border will be bare.
When you prune spring-blooming shrubs after flowering, cut out dead wood and thin out remaining branches, retaining well-placed ones to emphasize natural outline and grace. It is usually possible to remove completely a few of the oldest branches so that strong, new shoots have opportunity to grow and take their places. This practice, continued over the years, results in gradual renewal of the framework. In some cases an old branch may be shortened to a point at which a strong, younger side branch springs from it. Don’t shear all branches to approximately the same length. This crew-cut technique results in several weak shoots growing from each cut end and a complete loss of naturalness and attractiveness. Shrubs to prune after they flower include forsythia, deutzia, mock-orange, shrub roses, spring flowering spireas, kerria, beauty-bush, weigela and Tamarfx parviflom.
Purpose: to prune, and limit size somewhat, of shrubs valued for their attractive berries such as barberries, cotoneasters, viburnums, snowberry, jetbead, winterberry, sweetleaf (symplocos), firethorn, bayberry, sea buckthorn (hippophae), Russian-olive, euonymus and holly.
Go easy. In the great majority of cases do no more cutting than absolutely necessary to keep the plant shaped a little, to take out dead wood and thin crowded shoots obviously too weak to flower and fruit well. An exception is the beauty—berry (callicarpa); if pruned in spring it fruits in fall.
Purpose: to encourage brightly colored young stems to show to advantage in winter, as should be done with red-stemmed dogwoods (Camus alba, C. stolonifera and C. Baileyi), golden-twig dogwood (C. stolonifera flaviramea) and white-stemmed blackberries (Rubus Cockburnianus and R. biflorus).
Cut all old: stems back to ground level before leaves appear. Afterwards fertilize.
Purpose: to keep plants from getting too big yet retain a somewhat informal appearance.
Consider carefully before cutting. Not all trees and shrubs can be kept small by pruning and still remain attractive. There are usually size limits below which it is not advisable to attempt to keep specimens. lf the space is not big enough for the shrubs or trees when pruned moderately, replace them with smaller kinds or make additional room by taking out neighbor plants. Butchering specimens each year to force them to conform to small spaces is poor gardening.
Pruning practices already described limit growth and if applied keep plants in bounds to some extent. Some plants, especially yews, junipers, Japanese holly, boxwood and certain other evergreens, can be considerably controlled by shortening back the previous year’s growths just before new growth begins.
Purpose: to maintain a hedge or piece of topiary (shrub trimmed in a formal, fanciful shape) that has reached maximum allowable size.
Shear just before new growth begins, cutting back very close to the bases of last year’s shoots.
Purpose: to encourage a young hedge to become large, thick and shapely.
Privet one of the common hedge plants is an example of a shrub which will grow according to the way you prune it. If unpruned (left) it will develop into a small tree and produce flowers. Given half-hearted pruning (center) it looks like a poor hedge. Pruned properly it makes a heavy hedge (right)
Shear just before new growth begins so that the hedge tapers slightly from base to top. Make the top square or round, preferably the latter. Cut so that no more than 6 inches extension in width (3 inches each side) and 6 to 12 inches in height are added in any one year. Too rapid extension may result in a weak, poorly branched bottom.
Pruning hedges starts at planting. Shear back about 6 inches when planting. Shear it back before new growth starts so that it gains no more than 6 inches of width nor 6 to 12 inches in height eah year until desired height and width are achieved. Hedges should taper to the top - the base being the widest portion.
Purpose: to rehabilitate a hedge that is too tall, too wide, not dense enough or poorly shaped.
Evergreen hedges need shearing too. Taxus (yew) hedges (left) can be trimmed severly since this plant also has hidden buds which will grow. Hemlock (right) doesn’t have this type bud; consequently only the very tips can be cut back - heavy wood will not sprount.
What you can accomplish depends upon the kind of hedge. If it is hemlock, arborvitae, spruce or other kind that does not produce new shoots from old branches and trunks when they are cut back there is little to do other than replant. lf the hedge is yew, privet, pittosporum, barberry, stephanandra, five—leaf aralia (Acanthopanax Sieboldianus) or other plant that “breaks” freely from cut-back old branches, prune as severely as you wish before new growth begins. Don’t hesitate to be drastic.
Purpose: to prune large trees
Let a professional tree surgeon do it if climbing or removal of heavy limbs is involved. Slips or mistakes may be fatal or cause serious injury. lf you do prune don’t leave stubs. When removing sizable branches iirst cut into the underside about 2 feet out from where the final cut will be, then saw completely through the limb a few inches farther out. Finally, remove stump flush with trunk or main branch, smooth surface with chisel or knife; coat with tree wound paint.
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