Pruning Landscape Evergreens
By Joan Allen
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Alberta spruce |
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University of Georgia |
Late winter through early spring is the best time to prune most evergreen plants. Evergreens can be divided into two broad groups, the narrow-leaved evergreens and broad-leaved evergreens. Narrow-leaved evergreens include most coniferous plants such as pine, spruce, fir, hemlock, yew, juniper and arborvitae. Broad-leaved evergreens include Rhododendron, azalea, Pieris, mountain laurel, holly, boxwood and Leucothoe. The coniferous plants are mostly grown for their attractive foliage and form while the broad-leaved evergreens are often grown for their flowers.
Pruning is done for various reasons including removal of dead, weak or diseased wood, maintaining the shape or size of the plant, or thinning and reinvigorating the plant. Specialty pruning is done to create formal effects such as clipped hedges, topiary, and shaped shrubs. To minimize pruning requirements in a more informal landscape, trees and shrubs should be planted in a location that will match their mature height and width.
Trees, with the exception of the smaller dwarf cultivars, should not be used in foundation plantings close to a home or building.
Pruning tools that you will find useful include hand pruners, lopping shears, a curved pruning saw, and, in some cases, hedge shears. There are two styles of hand pruner: bypass (scissor type cut) and anvil (blunt cut). The scissor style will make a cleaner cut but either type will work. Lopping shears have long handles and are used with both hands to trim branches. Pole pruners are also useful if you need to trim or prune branches on trees that are high off the ground.
Evergreens should in general be pruned less severely than deciduous trees and shrubs because of their slower growth rate. Do not try to do major pruning to most of them in one season. Most needle-leaved evergreens do not have latent buds on the older wood so pruning cuts should be made where there is green foliage. Right above a whorl of needles (ie pines) or at an adjacent branch (ie arborvitae, juniper) are the best places prune. Some needled evergreens, including yew, hemlock, juniper and arborvitae can be pruned more heavily. These can be pruned in early spring and withstand a second light pruning during June if necessary. Make cuts close to an adjoining branch to facilitate healing of the wound by the plant.
Broad-leaved evergreens that bear spring flowers should be pruned right after flowering. The Rhododendrons, azaleas, Pieris, mountain laurel and leucothoe form flower buds in late summer and fall for the next spring bloom period, so pruning in late winter or early spring will remove some of the flowers. In addition to pruning branches to maintain shape and size, remove spent flowers. The energy resources that the plant would have expended for seed development will then be available for new shoot growth and flower bud formation.
Prune out dead, diseased or broken branches or growth at any time during the growing season. Prune out diseased tissue during dry weather and disinfect the pruning tool between cuts by dipping it in either 70% alcohol or a 10% solution of household bleach.
This time of year, some evergreens show evidence of winter injury. Exposure to sun or wind during the winter can cause desiccation of the leaves because water lost to the atmosphere through transpiration cannot be replaced by the roots when the ground is frozen. Browned foliage is often evident on one side of the plant and usually the outermost tips of branches are affected. This damage can appear to be quite severe, but the buds may still be alive. Check to see if the branch or twig is dead by scraping a tiny bit of bark off and seeing if the inner tissue is green. If it is, wait until after the new growth begins in later spring and the shrub may be able to recover. Dead branches can be pruned off as necessary at this time.
Dwarf Alberta spruce is a popular landscape plant that usually requires no pruning. An interesting abnormality that occurs on 1 of every 10-20 mature dwarf Albertas is called genetic reversion. This dwarf conifer is a cultivar of white spruce (Picea alba). Occasionally one branch or growing point on the tree will revert to the full-sized white spruce genotype and produce growth that looks like a tree growing out of a tree! If this occurs, it is best to prune out this growth when it is noticed because it will eventually dominate the dwarf tree.
For more information on pruning evergreen plants and other garden and landscape information, contact the UConn Home & Garden Education Center toll free in Connecticut at (877)486-6271 or by email at ladybug@uconn.edu.
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