Winter is a good time to prune trees and shrubs.
Many trees and shrubs can be pruned in the winter, said a University of Illinois Extension horticulture educator.
"However, due to the weather being on the cold side, it is not always the most pleasant of gardening activities," said James Schuster. "Summer-blooming shrubs may actually benefit when pruned correctly in the winter. Summer-flowering shrubs produce their buds and, thus, their flowers on the new growth produced in the spring. The more new shoots that the plant grows, the more flowers."
There are some woody plants that often die back to the ground during the winter. These plants tend to produce an abundance of flowers on their new growth. Butterfly bush and some of the hydrangeas are examples of this type.
"Spring-blooming shrubs can be done, too," Schuster noted. "Winter pruning of spring-blooming shrubs is less stressful to the plants. However, you will be reducing the number of flowers if you thin them now. If you just lower the height of spring-blooming shrubs, you will remove almost all of the flowers without improving the health of the plants.
"You need to thin the plant of one-fourth of the largest stems near the soil line to improve the plant's health. Do not reduce the height of the remaining stem in order to have spring flowers."
Spring-blooming shrubs like potentilla or Anthony Waterer spirea need to have every stem cut almost down to the ground every five to eight years, he added.
"Winter pruning is also less stressful on these types of shrubs than if you wait until they are done flowering," said Schuster. "These plants may not have any flowers the following spring. However, these plants will often produce flowers later in the summer and then in the following years will bloom in the spring."
Schuster said there are three pruning methods.
- "The first is called rejuvenation. All the stems in the plant are cut off close to the ground," he said.
- "The second pruning method is called renewal. Plants are thinned of about one-fourth of their stems near the ground.
- "The third pruning practice is called heading back. This term is often confused with topping. Topping is butchery because plants are cut at some predetermined height even if it is destructive. Heading back is pruning back to a leaf, leaf bud, leaf scar, side branch, and main branch or to the trunk.
"Heading back is the pruning practice that is for single-stem shrubs, deciduous trees, and evergreens--both needle and broad leaf."