November 11, 2015
The leaves have fallen off the trees and the perennial beds have died back and need to be cut back. This gets gardeners looking at their other plants and they are thinking that maybe it would be a good time of the year to cut back some of the shrubs. Many times I will have customers come into the store and ask if it was Ok to cut back their (fill in the blank) shrubs. Depending on the shrub, that may have been a “too late” question. Yes, there are shrubs that can be cut back in the fall. There are others that you could cut back in the fall if you don’t mind not having flowers on the shrub next year and there are shrubs that probably shouldn’t be cut back in the fall because it may lead to potential winter damage. Let’s take a few minutes to go over some basic fall pruning.
If you have plants that flower in early spring, you should not cut them back in the fall. For example, rhododendrons and azaleas can be cut back after they flower in the spring. During the late spring or summer, they set their flower buds for next spring. If you prune back these plants in the fall, you are cutting off the flower buds. No flower buds means no flowers in the spring. If your shrubs flower in the spring, do not cut them back in the fall.
There are many summer flowering shrubs that can be cut back in the fall. Many summer flowering shrubs set their flower buds on the new growth that comes out in the spring. This would be butterfly bushes and Rose of Sharon. Rose bushes would fall into this category but in New England you need to be careful with fall pruning on Rose bushes. If you prune in late fall, the rose canes may not have enough time to “seal “ the cuts. We get dry winter winds that can pull moisture out of those cuts and cause damage to the canes. Of course, if the rose bushes get covered by 9 feet of snow like last winter, you probably would not have to worry about the canes drying out. If you can do long range weather forecasting, you can have a good answer as to whether to cut or not cut rosebushes now! Your ornamental grasses can be cut back in the fall. You may chose to leave the blades long to enjoy the winter beauty of the dried grass against the snow. However, you do need to cut them back first thing in the spring. If you don’t, the brown blades will be intermixed with the new green blades. Once the green blades get a head start, it is the dickens to cut out the old blades without cutting the new blades. Hydrangeas and clematis are two plants that either can or shouldn’t be cut back in the fall depending on the variety. Many of the hydrangeas set their flower buds on the canes that formed this summer. There are three different pruning times for clematis and the correct pruning time is based on the variety of clematis that you have. This is one of the times that knowing the variety of plant that you have will determine when you prune your hydrangeas or your clematis.
Pruning back shrubs in the fall can be a tricky proposition. Yes there are plants that can be pruned back in the fall. There are others that can be pruned in the spring. The easiest rule of thumb is, if the plant flowers in the spring prune it after it is done flowering. If the plant blooms in the summer, you can prune it now or in the spring. (Keep in mind the exceptions I mentioned earlier.) If you are not sure, ask before you prune.
Well, that’s all for this week. I’ll talk to you again next week.