David Robson Extension Educator, Springfield Extension Center, University of Illinois
Yard & Garden
The Rose is the Flower for the Masses
Knock-Out roses are making it easy to landscape with the National Flower
June is National Rose Month, which President Ronald Reagan designated as our National Flower. Sadly Everett Dirksen could never achieve the same designation with the marigold.
Almost 50 years ago, Dr. Griffith Buck at Iowa State University started work on hardy roses that need little care. His criteria for success were roses that needed little to no winter protection, were black-spot and mildew resistant, and bloomed several times throughout the summer if not continuously.
Others around the world were doing the same, and about 30 years ago, success started pouring in. Most of this breeding work led to the newest class of roses for the gardeners: the landscape or shrub rose.
You could safely say that these were the roses for the masses.
The phrase “landscape rose” is a great marketing term, saying so much more than “shrub rose.” There’s the impression that landscape roses fit nicely into the landscape and, like most landscape plants, require little care. For most of the time, that’s true.
Of all the landscape or shrub roses, the Knock-Out series seems to be taking the forefront.
Knock-Out roses first made the headlines with a splashy red, semi-double flower that bloomed all summer. Plants are resistant to black spot disease. That in itself would be enough to shout from the highest mountain. They are also resistant to powdery mildew, and winter hardiness isn’t a problem unless you’re in Alaska.
Word of warning: “resistant” doesn’t mean immune. Occasionally, you’ll find black spot disease on many of the landscape and shrub roses, but it doesn’t appear to denude them like it does the hybrid teas, and others.
So far, the biggest problems have been with Japanese beetles (next month’s topic) and rabbits.
Rabbits tend to eat anything during the winter and the stems of the roses seem particularly flavorful. Fencing helps, but that sort of defeats the purpose of the landscape rose.
The original Knock-Out rose was red. That was followed by a pink and white form. In the last couple of years, we’ve had a double flower form, which are twice as large and as full as the initial Knock-Out.
This year, there’s a yellow flower form, though it may be hard to find as everyone seems to be grabbing them up. Just be patient and keep asking for it.
There are other shrub and landscape roses besides the Knock-Outs. Check the tags carefully for what they promise and what they don’t, or more likely, what’s not listed on the tag. Look for disease resistance and winter hardiness.
Anything that says the rose will do well in the shade is probably not accurate. Roses, even the landscape types, need at least six to eight hours of direct sunlight per day.
Two things to remember about landscape roses:
David Robson is an Extension Educator, Horticulture, at the Springfield Extension Center, University of Illinois Extension, P.O. Box 8199, Springfield, IL 62791. Telephone: 217-782-6515.
© 2008 Illinois Country Living Magazine.