A high school friend of mine, Kurt, recently asked a great question about pruning Knock Out roses. He has heard many different opinions and recommendations about how to do this.
In 2000, Conard Pyle Nursery introduced the first Knock Out rose that was created by William Radler. This rose stormed the market and set the scene for the introduction of so many new roses that are quite popular today.
Shrub roses have actually been around for a long time, but the older varieties weren’t that pretty and couldn’t hold a candle to the beautiful hybrid tea and floribunda roses. However, the latter two take quite a bit of care and people have been looking for a low-maintenance rose for quite a while.
Compared to traditional roses, shrub roses have smaller leaves, a bushy full vigorous growth and more but smaller flowers. The flowers are considered self-cleaning, which means that they drop their petals and don’t require deadheading in order to encourage more blooms. The plant then produces more blooms that cover the entire plant.
Knock Out is a shrub rose. Radler, the breeder, started in the 1970s to develop a plant that had good habit and flower characteristics. He worked for years to develop a low-maintenance variety that looked good and was resistant to black spot, a major disease problem of roses.
He didn’t hit upon Knock Out until 1989. And when this plant was introduced, it took the market by storm.
As I mentioned above, Knock Out and other shrub roses (Oso Easy, Carefree, Meidiland and many more) are self-cleaning and do not need deadheading, as do hybrid tea and multiflora roses. These will have around three to four sets of blooms during a growing season. I had four last year because the season started so early.
I don’t prune during the season unless a branch is broken. Otherwise, I let them go as they are. However, last spring, in early April, I cut them all back to about 12 inches above the ground. I also take out any broken or dead branches and shape the plant if needed.
Pruning in the early spring helps to keep the plants from getting straggly. Technically you could let them go without a spring pruning, but they tend to get a little straggly in their shape.
That’s it, Kurt: These roses are very easy to grow. But, wait. There is one other thing that tends to get me worked up about this plant. When we find a plant that we really like and it’s easy to grow, all of a sudden they are everywhere. Keep in mind diversity in the landscape is essential.
There are lots of other varieties of shrub roses besides Knock Out, and they are equally as good (or better in some cases). Next week I’ll continue with the other pet peeve I have about Knock Out.