Most shrubs and trees are best suited to be pruned in the fall after most of the leaves have dropped. This gives you the best view of the plant’s structure and allows you ready access to the interior of the plant where most problems occur. Remove any broken and dead branches and also any branches that are growing toward the interior of the plant.
Pay close attention to any branches that are in contact with each other or will be soon; Rubbing away the bark will allow disease to flourish instead of the shrub or tree. Removing upright branches will allow the tree to spread, while removing horizontal branches will encourage more upright growth. You should be familiar with the trees and shrubs planted on your property and prune them accordingly. Certain plants are more susceptible to winter weather than others, so it is best to hire a skilled professional if you are not experienced in pruning. Even with fall pruning, there will most likely be a need for some pruning in the spring to remove any damaged braches.
Common Pruning Types are:
Crown Thinning - Removing branches throughout the tree to promote growth and maintain tree health.
Crown Raising - Removing lower branches to provide space for pedestrians, vehicles, or timber. After pruning the remaining crown should be no less than two-thirds the height of the tree.
Crown Reduction - Also known as Drop Crotch Pruning, this is used when the tree has grown too large for its space. Prefered over topping to maintain a more natural appearance.
Some general tips are as follows:
Major limbs growing at a narrow angle to the main trunk (less than a 45-degree angle) is likely to develop a weak crotch and may split during heavy winds and ice loads. Remove branches that have narrow crotch angles.
Remove branches that grow inward or threaten to rub against nearby branches.
Remove branches that grow downward from the main limbs, which may interfere with mowing and other maintenance practices.
Lateral branches should be no more than one half to three-quarters of the diameter of the stem at the point of attachment.
Avoid removing all inner lateral branches as this can lead to sun-scalding, numerous sprouts, and weak branches.
Crown thinning - branches to be removed are shaded in blue; pruning cuts should be made at the red lines. No more than one-fourth of the living branches should be removed at one time.
Prune branches damaged by insects, diseases, winter cold or storms below the damaged area. For diseased branches, cut several inches below the infected area and thoroughly clean tools before moving to another tree.
Trees such as Bradford pear, ornamental cherry, and crabapple form vigorous shoots (Also called suckers or bleeders) at the base of the trunk and many upright succulent shoots (watersprouts) along the main branches. These shoots starve the tree of valuable nutrients and detract from the tree’s overall appearance. Remove them while they are young.
Some trees develop upright shoots, which compete with the main trunk for dominance. Remove these shoots if you want to maintain a conical or pyramidal growth habit.
Broadleaf evergreens, like magnolias and hollies, usually require little or no pruning. In fact, most broadleaf evergreens develop a naturally symmetric growth habit when left alone. Most upright-growing plants in the conifer group such as spruce, pine, cedar and fir have branches spaced evenly around the main trunk. They develop a symmetrical growth habit and become quite large at maturity. If planted in open areas and given plenty of room to grow, they require minimal pruning. Avoid cutting back into the hardened older wood because new shoots will not grow and the form of the plant will be destroyed.
Ornamental grasses should also be pruned back severely unless you prefer their dried appearance. If heavy snowfalls or ice storms occur in your part of the country, then this look will be quickly destroyed. Either way, they will have to be cut back to promote new growth in the spring so you may as well do it in the fall when all of the other work is ongoing.
When to Prune
Conifers (Evergreens) may be pruned any time of year, but pruning during the dormant season may minimize sap and resin flow from cut branches.
Hardwood trees and shrubs without showy flowers: prune in the dormant season visualize the structure of the tree, to maximize
wound closure in the growing season after pruning, to reduce the chance of transmitting disease, and to discourage excessive sap flow
from wounds. Recent wounds can attract insects that spread tree disease; open wounds on oaks are known to attract beetles that spread the oak wilt fungus. Take care to prune these trees during the correct time of year to prevent spread of these fatal diseases. Contact your local tree arborist to find out when to prune particular tree species in your area. Typically the best time is during the late fall and winter.
Flowering trees and shrubs: these should also be pruned during the dormant season for the same reasons stated above; however, to preserve the current year’s flower crop, prune according to the following schedule:
- Trees and shrubs that flower in early spring (redbud, dogwood, etc.) should be pruned immediately after flowering (flower buds arise the year before they flush, and will form on the new growth).
- Many flowering trees are susceptible to fireblight, a bacterial disease that can be spread by pruning. These trees, including many varieties of crabapple, hawthorn, pear, mountain ash, flowering quince and pyracantha, should be pruned during the dormant season.
- Trees and shrubs that flower in the summer or fall always should be pruned during the dormant season (flower buds will form on new twigs during the next growing season, and the flowers will flush normally).
Dead branches: can be removed any time of the year.
References
ANSI Z133.1. 1994. Safety standards. American national standard for tree care operators. Washington, DC: American National Standards Institute. ANSI A300. 1995. Standard practices for tree, shrub, and other woody plant maintenance. Washington, DC: American National Standards Institute. Fazio, J. R. ed. 1992. Don’t top trees. Tree City USA Bulletin No. 8. Nebraska City, NE: The National Arbor Day Foundation. Harris, R.W. 1994. Clarifying certain pruning terminology: thinning, heading, pollarding. Journal of Arboriculture 20:50-54. ISA Performance Guidelines Committee. 1994. Tree-pruning guidelines. Savoy, IL: International Society of Arboriculture. Ryan, H.D.P. III. 1994. Arboricultural pruning methodologies. Arborist News Volume 3(4):33-38. Shigo, A. 1991. Modern arboriculture. Durham, NH: Shigo & Trees, Associates. Shigo, A. 1989. Tree pruning: a worldwide photo guide. Durham, NH: Shigo & Trees, Associates.
