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Pruning deciduous trees and shrubs

By: Khursheed Mama, CSU Extension Master Gardener in Larimer County | The Surveyor | March 12, 2021 | Local News

Pruning Deciduous Trees and Shrubs

This winter has not been consistent in temperature or precipitation, but cooler nighttime temperatures help keep plants dormant. Now is the time to prune your deciduous trees and shrubs. It is recommended to remove no more than 25% (10-15% in stressed trees) of a tree’s canopy each year. This will help eliminate stress to the tree and give it the ability to seal over pruning wounds. However, removing crossing branches, water sprouts and suckers, and dead wood will help promote tree health and reduce potential damage from storms.

When pruning make good pruning cuts and use sharp tools. A pruning saw and a pair of hand pruners are often the most useful tools. Aim to keep your pruning cuts less than 2” in diameter. For large branches, use the three-cut pruning method, diagramed below (graphic courtesy of the University of Missouri). Do not leave “stubs”.

For more detailed information on pruning ornamental and shade trees, refer to https://cmg.extension.colostate.edu/Gardennotes/615.pdf. For details on pruning fruit trees, refer to https://extension.colostate.edu/topic-areas/yard-garden/training-and-pruning-fruit-trees-7-003/.

Pruning Evergreens

Appropriate selection and siting of evergreen trees and shrubs will reduce the need for pruning, but on occasion a dead or damaged branch may need to be removed to maintain plant health. While shearing shrubs is considered to be quick and easy, it often results in unattractive browning and abnormal plant form. Evergreen trees can be pruned to remove multiple leaders. If you’re trying to control growth on pine trees or shrubs, you can pinch back or prune the emerging candles by half. For additional information on pruning firs, spruce, pine and junipers, refer to https://cmg.extension.colostate.edu/Gardennotes/617.pdf.

Pruning Flowering Shrubs

Summer-blooming shrubs that bloom on new growth (e.g. many hydrangea, potentilla, blue-mist spirea, etc.) can be pruned during the late winter/early spring. However, shrubs like lilacs and forsythia are best pruned shortly after they have flowered; pruning spring-blooming shrubs now will likely remove blooms, since you’re pruning off the flower buds. Like evergreens, it’s not recommended to shear flowering shrubs, as it can lead to unattractive growth in the center of the shrubs. More details on pruning shrubs is available through https://planttalk.colostate.edu/topics/trees-shrubs-vines/1713-pruning-shrubs/ and https://cmg.extension.colostate.edu/Gardennotes/616.pdf.

Another shrub pruning approach is rejuvenation and renewal pruning. Rejuvenation is cutting back the entire shrub to a few inches above ground. This will encourage the plant to sucker. This is successful on spirea, potentilla, and burning bush. Keep in mind the re-growth will depend on the overall health of the shrub, so give the plants some extra water following pruning. Renewal pruning is thinning plants and removing one-third of the oldest branches over a period of three years. This works well on red-twig dogwood and lilacs.

If you want to watch the CSU Extension video on renewal versus rejuvenation pruning, check it out here: https://www.youtube.com/watch?v=q88db-I3aw8

Pruning Roses

Wait until mid-to-late April to prune roses; pruning too early can result in winterkill from late spring frosts and freezing temperatures. Roses are usually pruned back to remove dead canes and to shape the plant. For more information on pruning roses, refer to https://planttalk.colostate.edu/topics/trees-shrubs-vines/1763-pruning-roses/

If you have gardening or landscape questions, please contact the CSU Extension Master Gardeners in Larimer County. They are available by email: [email protected] or you can leave a message for them to return your call: 970-498-6000.

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