By Jim Crawford
University of Georgia
It’s every homeowner’s dream: the beauty and color of landscape
flowering plants without a lot of maintenance to keep them
healthy and vigorous.
Thanks to Canadian rose breeder William Radler, we can now plant
Knock Out roses. They’re exceptionally hardy and maintenance-free.
Before Radler’s creation, most of the roses we had were bred in
California, where the humidity and warm temperatures created
roses that weren’t as tolerant of harsher environments.
The Knock Out roses I’ve planted didn’t even lose their blooms
when transplanted, which usually happens with other plants due to
the shock of being moved from the container to the ground.
They’re fast-growing plants that will fill in nicely as a
background for shorter, colorful annuals. You see them popping up
more and more in the landscape as people become acquainted with
their looks and the ease of their establishment and care.
Intentionally exposing plants to diseases
During the breeding process, at one time Radler had more than 600
rose seedlings in his basement. He purposely inoculated these
plants with black spot pathogens and used overhead sprinkling to
induce disease. He did this to see which plants didn’t become
infected.
He settled on a cross between “Carefree Beauty” and “Razzle
Dazzle,” a floribunda rose. When this patented rose was released
by Conard-Pyle and Star Roses, it sold 250,000 plants the first
year.
It was recognized as an All-American Rose Selection and received
the Texas Superstar Award and Arkansas Select Award.
Knock Out roses are a knockout
Radler’s new plant, the Knock Out rose, ranges from 3 to 5 feet
tall and equally wide. It produces multiple clusters of terminal
blooms, each 3 to 3.5 inches across. These very light, fragrant
flowers come in red, pink and blushing pink and will bloom from
spring until frost.
Humidity doesn’t seem to bother the Knock Out rose, and it’s
drought- and cold-tolerant. It’s somewhat shade-tolerant but does
need about six hours of full sun per day.
True to its low maintenance reputation, the Knock Out rose
doesn’t require deadheading and is resistant to aphids, powdery
mildew and black spot, the scourge of rose enthusiasts.
Plant Knock Outs during their dormant season between November and April. (They are so tough, you could probably plant them anytime of year.) Choose a well-drained sites with good air movement.
It’s perfect for grouped planting or even hedges. The foliage
turns from a lustrous green to burgundy in the fall, and the new
growth is slightly burgundy, too.
Lightly fertilize, prune slightly
These roses require a light fertilization every four to six weeks
with a 12-6-6 or 10-20-10 fertilizer. Prune any canes growing
straight up by simply cutting them in half. Pay close attention
to the bud orientation, so they’ll grow to fill in the gaps in
the canopy and establish the desired shape.
Knock Out roses are practically foolproof. The only things I’ve
seen that may cause problems are improper soil pH and not enough
sunlight. To test your soil’s pH, bring a soil sample and $8 to
your local UGA Cooperative Extension office. To find your local office, call 1-800-ASK-UGA1.
We planted two this spring at the Cooperative Extension office in
Louisville, and they’ve already grown to 3 feet by 3 feet with
constant blooms. If you aren’t an experienced rose grower, I
think you’ll be thrilled with these roses. If you’re already a
rose gardener, you’ll love not having to spray for diseases and
insects.
