“Pruning is one of the most important tasks to keep shrubs and bushes healthy,” explained Ross Penhallegon, horticulturalist and pruning expert with the Oregon State University Extension Service. “Yet pruning often gets neglected or forgotten.”
Shrubs that flower in the summer and fall are blooming on this year’s growth. They should be pruned early in the dormant period or very early spring so there’s plenty of time for new growth to form and bloom.
Shrubs can be pruned drastically if they get out of hand and need rejuvenation. Multi-stemmed species such as spirea and forsythia can be heavily pruned by removing the older stems or branches, lowering the height of the plant. Rhodies and azaleas can be heavily pruned to 12-14 inches or just above buds that are on the lower part of the plant.
An overgrown shrub with a single lead or trunk growth form needing rejuvenation should be gradually pruned down or brought under control to maintain the natural form of the plant. Don’t be tempted to shear off the top of this kind of plant. Always cut back to a good side branch. Shearing may be faster, but it will produce a leggy plant with brushy growth at the stem ends. Each cut will often produce two more branches. Some large shrubs, like laurel, will sprout from bare wood even when they’re cut back nearly to the ground. Evergreen shrubs, both broad-leafed and needled, should not be pruned back to bare wood.
About Garden News from OSU Extension Service: The Extension Service Gardening web page, http://extension.oregonstate.edu/community/gardening, links to a broad spectrum of information on Oregon gardening, such as tips, monthly calendars, how-to publications, audio programs, the Master Gardener program and “Northwest Gardeners e-News.”
By Judy Scott, O.S.U., Corvallis Ore
Source: Ross Penhallegon, O.S.U.Extension Service