News Release

Pierce County Office

Diana Alfuth, Pierce County Horticulture Educator

February 12, 2007

It’s Pruning Time

Pruning trees and shrubs is important for several reasons. Pruning can help control a plant’s size, influence flowering or fruiting, determine a plant’s shape, and maintain the health and appearance of the plant. Now is the best time to get out and prune most of your deciduous trees and shrubs.

Late winter, meaning February and March in our area, are good pruning times for a variety of reasons. You can see the overall branch structure easily without leaves blocking your view, and most insects and disease-causing organisms are dormant. Any pruning of oak trees should especially be done at this time of year to prevent the spread of oak wilt.

Keep in mind a couple things before deciding to prune. Some trees and shrubs that are pruned in late winter will bleed or ooze sap in early spring until the pruning wound heals over. This is common on maples, willows, birch and elms, but it does not hurt the tree at all—it just might make for an unsightly sticky mess.

Also keep in mind that any trees or shrubs that bloom in early spring have formed their flower buds last year, and pruning now will remove some of those buds and result in fewer spring flowers. Examples of plants affected in this way include lilacs, apples and crabapples.

Always use sharp pruning tools to make clean cuts which will heal faster. Also be sure to disinfect your pruning tools by dipping in alcohol or a 10% bleach solution between cuts to prevent the unintended spreading of disease.

When deciding what needs pruning, start with the “Three D’s”. Prune away anything that is dead, dying, or diseased. Any branches that have bark falling off are dead and will not recover. Always prune branches back to the next healthy branch. In other words, prune away the whole branch, and do not leave a stub or partial branch attached. However, do not prune flush with the trunk, or you will leave too big of a wound. Prune just outside the branch collar, so that a small protrusion will remain.

Trees newly planted last year should not be pruned unless there is damage to a branch. Maintain as many leaves as possible on young plants so they can conduct photosynthesis and create energy for growth. Once the young tree becomes established after 3-4 years, prune to encourage good scaffold branches and a good canopy. Remove any crossing branches, branches forming a narrow crotch angle with the trunk, water sprouts or root suckers. If the tree has a double leader, remove one of them to prevent problems in the future. Do not remove more than 1/3 of the canopy or it may overly stress the plant.

Older trees, if pruned properly when young, rarely need any pruning unless branches have sustained damage or died back for any reason. When removing larger branches, be sure to use a 3-point pruning method to prevent the bark from peeling back down the trunk as the large branch falls. Hire a certified arborist to prune larger limbs and remove trees, as it can be dangerous work, especially if buildings or powerlines are nearby.

Deciduous shrubs also can benefit from regular maintenance to maintain their form, health, and flowering ability. As shrubs get old, they often don’t flower as well. Pruning away old wood will encourage new growth resulting in better flowering and fruiting.

If a shrub is too big for its location, heading back can reduce its size. Rather than shearing the shrub into an unnatural form, trim each branch back to the next larger branch or to a bud. Do not leave branch stubs, which will invite diseases and insects, and look unsightly in winter when leaves are gone.

Shearing should be used only on formal hedges. An exception is the common spireas, such as ‘Little Princess’ and ‘Goldflame’, which can be sheared off about 6-8 inches from the ground. They will shoot up new growth in spring and form a compact mound of foliage with good flowering in summer.

To rejuvenate an older, multi-stemmed shrub that is not flowering well, such as old fashioned lilacs, remove 1/3 of the biggest stems all the way to the ground. This will encourage new shoots that will produce flowers in future years, and will shorten the overall size of the shrub as well. This type of pruning is good for all multi-stemmed shrubs, including red-twigged dogwoods. Younger stems on red-twigged dogwoods provide better winter color than older, rough-barked stems.

Selectively pruning the tips of branches will encourage side branching and can increase the bushiness of a shrub. It can also be used to direct the new growth to improve the overall shape of the shrub.

After making your pruning cuts, allow the plant to heal naturally, and avoid the use of wound dressings or tree paint. These compounds have been found to slow the plant’s natural wound healing ability, and may result in more disease and insect problems. The only exception would be in the case of oaks that are pruned in summer because of damage by storms or other causes. Sealing the wound with a paint or dressing in that case is important to keep out the insects that transmit the oak wilt fungus.

For more information about pruning your trees or shrubs, or any other horticulture issue, contact Diana Alfuth, Horticulture Educator, Pierce County UW-Extension office, 273-6781, or diana.alfuth@ces.uwex.edu.

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