Roses and hydrangeas are the two plant types for which I consistently asked questions. I don’t think it is an exaggeration to say that every day during the spring and summer someone asks me a question about either Endless Summer Hydrangeas or Knockout Roses. These are two beautiful plants that many gardeners either have already planted in their yards or are considering planting. For this column, I have asked Tim Wood, the Territory Manager for Star Roses and Plants to help by answering a few questions about Knockout Roses.
Tim, can you tell us a bit about the breeding history of the Knockout Rose?
The Knockout Rose was bred in the backyard of William Radler outside Millwaukee WI.
Will was looking to breed a rose which could be grown on its own roots as opposed to budding, increase hardiness, and improve disease resistance. The prolific flower power was a fortunate result of the cross.
What makes a Knockout rose different from other roses?
What makes The Knockout Rose different from other roses is the exceptional disease resistance to Black Spot, prolific flowering, cold hardiness, and its ability to grow on its own roots.
Why do you encourage gardeners of all ability levels to plant Knockout Roses?
It’s the longest flowering and easiest flowering shrub to grow in the landscape. The Knockout Rose requires one basic thing to provide years of success. Trimming by 2/3’s every spring, which stimulates continuous flowering, and helps keep the plant healthy. They like to eat, so slow release fertilizer in the spring will also help.
When referring to Knockout Roses the phrase “the Family of Roses” is frequently used. Why is that?
They are all from the same breeder, many with the same parentage or mutations of other Knockouts. As a result they are all related, and are family.
What are a few of the differentiating factors between the 10 different Knockout Roses?
We have 3 with double flowers The Double Knockout, The Pink Double Knockout, and The Coral Knockout. A compact form in the White Knock Out, A fragrant variety in The Sunny Knockout, and multiple varieties with different shades of Red and Pink with single flowers.
Which rose do you have the most of in your yard?
At one point I had several of each of The Knockout Family, over time I have removed most to make room for new test varieties. However I have two of The Sunny Knockouts remaining, and one of the original The White Knockout Rose’s. The Sunny Knockouts made the cut due to the summer long fragrance, and prolific flowering. The White Knockout rose I left has outstanding habit, foliage color, and flower power. They are also the most cold hardy (zone 4), and my two personal favorites.
In what environmental conditions do Knockout Roses grow best?
6 or more hours of sun.
What type of care do Knockout Roses require?
Trim them by 2/3’s in early spring, and apply a well balanced slow release fertilizer immediately after trimming.
In Northern Illinois, should Knockout Roses be cut back? When do you recommend that this be done?
The Family of Knockout Roses should be cut back by 2/3’s in early spring. Trim just as they are breaking dormancy in spring.
If a gardener wants to fertilize their Knockout Roses, what type of fertilizer do you recommend?
A well balanced slow release fertilizer.
Are there any other plant care products that you recommend for the care of Knockout Roses?
Mulch.
If our readers want more information about Knockout Roses, what resources are available to them?
Visit our website starrosesandplants.com or theknockoutrose.com
Kathleen Carr is the owner of The Growing Scene, Inc., a garden center and landscaping company. She can be reached by calling 815-923-7322 or Kathleen@thegrowingscene.com. Have a gardening question? Please contact her. She may address it in an upcoming column.
