One of our rose family recently posted a question on our discussion forum about pruning back blind shoots this late in the season. Their concern was promoting new growth close to a potential frost. (They live in Ottawa, Canada)
First of all if you are not familiar with the term “blind shoot” let me explain what it means.
A blind shoot is a stem that grows and grows but a flower never appears at the end of it. There are a few reasons why this happens. The most common one is a late frost in spring that kills the tiny rose buds before they can fully form. Other causes can be lack of nutrients, shortage of light and tiny midges. But generally it’s frost.
The “cure” is to simply cut the stem back as if deadheading and it should produce a new stem that will flower.
That’s fine early in the season.
But our rose family member’s question brings up an important point about going into fall. A great deal of trimming of your roses late in fall is not a good idea because it does stimulate new growth. And that new growth is tender and will likely be severely damaged by a hard frost.
During late fall I would advise you not to trim your roses much if at all. Besides risking damage to new growth you also inhibit the rose from setting hips, which is part of their going dormant. Additionally rose hips are a valued source of winter food for birds so it’s nice to keep them on.
If you do need to do some trimming late in the season on an out of control rose wait until you have had two good frosts. After that the rose should be shutting down and you can go ahead and do some trimming without the risk of stimulating a lot of new growth.