On the topic of winterizing knockout roses, I have found all kinds of conflicting information out there on whether it should be done and what techniques are appropriate. Granted, most were coming from amateur gardening blogs, I could not find a definitive resource out there. I decided to interview with our horticulturalist to get the facts straight. Here is what I found out:
Q. What is the importance of covering roses? Is this necessary in our area?
A. Yes, it is absolutely necessary. We live in an area that gets well below freezing and we get several days above freezing throughout the winter. Covering roses is not only important to guard from freezing temps but to protect from the continual thawing and freezing cycle that can happen above ground on a sunny day. Once the plant starts to thaw it lowers its natural defense in order to start growing again. If the plant goes into this state or [“comes out of dormancy”], it will die with the next cold night.
Q. I have found many conflicting gardening resources stating how to cover roses, everything from Styrofoam cones to wire mesh filled with straw and leaves. What have you found to be the best method for covering roses?
A. A mound of mulch covering the crown, the base where the canes grow from, will be sufficient. The rest of the plant will need to be heavily pruned in the spring so any dieback that the canes experience will be removed.
Q. You mentioned pruning, what about cutting them back in the fall? Many pages have said to leave them alone, some have said to cut back as branches die, while others have said to cut them back pretty far and pluck all the leaves off to aid in keeping moisture in. What are your thoughts on this?
A. Cutting roses back in the fall is important to decrease the surface area that moisture can escape from in the winter winds. It is important not to cut back too far. We leave the plant 24" or higher depending on age. Cutting the plant too short will kill it. If you cut back too far, it will shock the plant and it will not have enough time to recover before freezing.
So there we have our answer. Knowing that there are various techniques out there ranging in cost and labor intensity, these are the techniques that work best for us:
- Cover roses using a mound of mulch to protect the crown.
- Cut back roses, being aware of not cutting back too far.
If you are one of our regular maintenance clients and have roses on your property, you will see us stopping by to winterize your roses in the next few weeks! If you have any questions please give us a call!