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Pruning is important for both trees and shrubs. Pruning is selectively removing unwanted twigs or branches. There are several reasons to prune: branch structure, form, disease eradication, shrub size control, to rejuvenate old shrubs, and to promote fruit and flower production. Additionally with trees, pruning allows you to lift the crown of a tree or thin the interior of a tree for the prevention of wind damage.
Begin pruning deciduous, or leafy, trees to correct any poor branch structure within the first two years of planting. Normally, nursery-grown trees have already received corrective pruning to help them develop properly. It is still important to remove any branches that cross or rub and any branches that break so that disease cannot attack through open wounds. Remove a few of the lowest branches each year to raise the canopy of the tree as the tree grows so that it is easier to walk underneath. This is typically not done on evergreen trees. It is also good to thin the interior of the tree’s canopy as it matures to allow wind to freely pass through to prevent damage. You should never have to prune a tree for height control if the proper tree was chosen for the site. The best time to prune deciduous trees is in late winter. Magnolia, Redbud and lilac trees are exceptions as the flower buds are set the previous year on old wood and pruning while dormant would remove the flowers. Prune magnolias and lilacs within 3 weeks after flowering. Oaks, in particular, should only be pruned in January and February so that they do not contract disease. Crabapples and other fruit trees are best pruned in March.
The natural form of an evergreen tree is usually the most desirable, and pruning should be limited to correcting growth defects and broken branches or maintaining its natural form. It is sometimes desirable to prune pines to promote dense, compact specimens. Do not cut the terminal leader of an evergreen tree unless it is extremely long or tall. Evergreen trees should be pruned before the new growth, often referred to as candles, is fully expanded or becomes stiff to the touch. This normally occurs in late June, so prune in early to mid June when the candles are about three-fourths elongated. Up to one-half of the new growth can be removed if necessary.
Deciduous shrubs are best pruned in the early spring when the leaves are still off. Fall or early winter pruning is the second best time, however, it can make the shrub more vulnerable to winter injury. The exceptions are early spring flowering shrubs such as azalea, forsythia, fothergilla, blue and pink flowering hydrangea, lilac, rhododendron, and white spring-flowering spireas such as snowmound and renaissance. These spring-blooming shrubs set their flowers on old wood about a month after bloom, therefore the proper time to prune is within a month after flowering.
Evergreen shrubs should be pruned to promote density, to remove any dead branches and for form and size control. This can be done almost anytime except August through November. Pruning during this time will promote late growth that is more susceptible to winter damage. Pine, spruce and fir shrubs are the exception, and should be pruned in early to mid June before the new growth becomes woody or hard to the touch.
Proper pruning tools should be used and each one has a specific job. For twigs and small branches up to one-inch in diameter, use a sharp by-pass pruner. Branches under 2 ½” in diameter require a stronger by-pass lopper for best results. Hand saws work best on branches up to five inches in diameter. For even larger limbs, a power saw is a better tool. Remember to sterilize your equipment between cuts when pruning species prone to disease, or any plant known to be diseased, to prevent the spread of infection. For large trees where it is difficult and dangerous to do your own pruning, we recommend using a professional tree service in your area.
Technique is important when pruning to promote safe and fast healing of the wound. To cut back twigs and branches, cut at a 45 degree angle about ¼ to ½” above a bud. Evergreen branches look best when the cut is near a side branch so that the result is more natural looking. When cutting large shrub branches or tree limbs, a three part cut can prevent damage to the plant. First make a small undercut 6-12” from the trunk. Now move out a few more inches and cut all the way through. This will remove the weight of the branch and prevent bark peeling. Now remove the stub by finding the “branch collar” first. The “branch collar” is a swollen collar right where the branch meets the trunk. Cut the stub off leaving the branch collar undamaged. This promotes faster healing of the wound. The latest research has shown that wound sealants and dressings actually can slow down the healing process. It is recommended that when trees susceptible to disease such as oak or elm receive wounds while the temperatures are above 50 degrees, that you use a wound sealant. The protection from insects and disease outweigh the detriments of slowed healing.
Protect the trunks of any smooth barked trees from winter sunscald by applying tree wrap in the fall before the snow arrives. Remember to remove the wrap in the spring before the weather warms so insects and diseases don’t make it their home. Some species such as pink and blue flowering hydrangeas, hibiscus, and other marginally hardy plants will benefit from some winter mulching for protection.
After the first season, apply a slow release fertilizer to all trees and shrubs. A good nitrogen-phosphorus-potassium ratio to look for on the bag is about 10-10-10. Do not go over 14 for any of the numbers. Follow the manufacturer’s recommendations for rate of application. Please do not fertilize the first season, as we applied a starter fertilizer when we installed your plantings.