Question: I have shrubs which have become overgrown and need to be pruned. I have been told there are some shrubs which should not be pruned in the winter or spring. What can I prune now?
Answer: March is an excellent time to prune most trees and shrubs. With deciduous plants it is easier to see what needs to be pruned when there are no leaves. The exceptions are spring flowering shrubs which already have their flower buds formed. Examples are lilac, spiraea, forsythia and viburnum. Pruning now would remove some of those flower buds and reduce the amount of bloom. The best time to prune spring flowering shrubs is within a month or two after their bloom. Shrubs which bloom after June develop their buds in the spring. Those summer flowering shrubs can be pruned now.
If you want to retain the natural shape and thickness of a shrub, do not use power clippers. Shearing multiple branches at the same time removes the tips of all branches and causes them to produce multiple branches from each cut. After two or three years plants become artificially thick. There is also a tendency to shear into boxes and balls which is also unnatural.
You can reduce the size of a shrub more by pruning one branch at a time. Take the longest branch and follow it inside the shrub several inches. Prune just above a side branch or remove it back to its origin. The surrounding growth will hide your pruning cuts. Continue this process by selecting the longest remaining branch until you have reduced the size to what you want. You should not reduce the size of a shrub by more than 25 percent.
Evergreen shrubs like juniper and arborvitae only have green tissue for a few inches on the outside of the shrub. If you prune too deeply, you will remove all green tissue. Brown branches will not produce new green growth. Any new growth to cover brown areas will have to come from other green tissue on the sides.
All the dead growth should be removed on rose canes down to green tissue. I like to remove all canes of hybrid tea roses which are less than pencil size. These thin stems produce poor flowers. All cuts should be made just above a node (bulge where a leaf was attached).
This is a good time to remove the dead top growth from perennial flowers. If you wait too long you may damage the new growth that has already started. This is also a good time to remove the dead tops of ornamental grasses.