Time to give the Knockouts a cut!
Today I saw the last petals fall from my Blushing Knockout Rose. It’s time for rose pruning! Repeat blooming roses like the Knockout, Drift, and Flower Carpet series, as well as others, perform their best with periodic pruning and fertilization throughout the growing season. They are by no means maintenance free, however they are very forgiving as far as timing on these treatments. Here’s what works for me…(keep in mind this is for shrub roses, not hybrid teas, grandifloras, or climbers)
My shrub roses begin the growing season as stumps that were cut back severely in late winter as the buds were starting to turn red. After the stumps really start to flush out new growth on their own, they get a granular fertilizer. I prefer granular or dry organic fertilizers for shrubs because they give a fairly consistent feed, unlike liquids which give a quick burst then dissipate. Fertilization is especially important for rebloomers in order to keep them growing, blooming, and healthy looking. A starved rose will still bloom, but it will show the signs of stress by mid to late summer much more clearly than will a fed rose. The stress can also lead to opportunities for disease and insect infestation.
The bloom cycle can last quite a long time, well over a month between the first flower opening and the last petal dropping. When it is over there are two options: do nothing or prune. Doing nothing will allow the pollinated flowers to form rose hips which are the rose bush’s fruit and are loved by certain wildlife. If you are growing your roses for the love of the bloom and not to feed wildlife, you should choose the second option. Pruning removes the spent blooms so that the shrub puts energy into growing and blooming instead of ripening fruit. Each time you prune the plant, it is also a good idea to fertilize. This cycle will happen multiple times throughout the growing season. One note of caution: the final pruning should be at least a month prior to the first frost date in order to allow ample time for new growth to harden off before winter and avoid cold damage.
To prune these shrub roses, first consider what it is you are trying to accomplish:
1. Remove the spent blooms.
2. Reduce the size of the plant so that when it blooms again it will be a good size.
3. Thin the branches to give good air circulation within the plant.
4. Remove damaged branches. Begin with a wholesale reduction in size.
I use use a pair of loppers and cut back the longest and thickest branches first, removing up to 25 percent of the overall size of the plant. Then clean up what’s left of the plant with a pair of hand-held pruners. Look for spindly or dead branches to remove, also congested areas of the plant should be thinned to a single dominant stem. When finished the plant will be a little shorter and narrower, a lot more sparse, with a well balanced shape.
This is a good time to check for and treat insect or disease problems. Roses are known for black spot. Fortunately my Knockout roses are resistant, and show no signs of that. On the other hand, Japanese beetle season is here, and my foliage is riddled with damage. I bought traps today that I will place well away from the roses, but more on Japanese beetles in another post.
When pruning is complete, be sure to clean up the debris. If you have had problems with rose diseases, bag up the material and get it off your property. I haven’t had disease problems, so the junk goes on the pile to get burned. Wrap up the project with a regular application of rose fertilizer following the directions on the label. In three to four weeks, your roses will be blooming again. Happy Summer!