Disease Resistance Trumps Color for Hitmaker
The Knock Out® Rose, a 2000 AARS Winner

From The San Francisco Chronicle by Rayford Reddell

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The Knock Out® revolution begins!

The Knock Out® Rose ushered in the millennium as a 2000 All-America rose in the shrub division.

When William Radler was only 9 years old, he bought his first rosebush at a local A&P market in Milwaukee. His parents warned him that it would bow to the hard Wisconsin winter, but young Bill was determined to coax his favorite flower into bloom by the following early summer, which he did. This initial success spurred a determination to improve upon the rose by conquering hardiness and disease resistance. Even as his optimism grew, it must have been impossible to imagine just how successful he was to become.
Bill Radler, Creator of The Knock Out® Rose

The Knock Out® revolution begins!

When William Radler was only 9 years old, he bought his first rosebush at a local A&P market in Milwaukee. His parents warned him that it would bow to the hard Wisconsin winter, but young Bill was determined to coax his favorite flower into bloom by the following early summer, which he did. This initial success spurred a determination to improve upon the rose by conquering hardiness and disease resistance. Even as his optimism grew, it must have been impossible to imagine just how successful he was to become.

After buying a 1 1/2-acre plot, which he labeled the Rosarium, he became a full-time rose breeder as a young adult. The early years were devoted to crossing after crossing of his parent roses in search of seedlings that matched his criteria for disease resistance, winter hardiness and steady cycles of bloom. His methods for breeding them included innovative techniques, such as deliberately inoculating plants with disease pathogens. He actually plucked foliage from infected plants and ground their leaves in a blender, then spread them on healthy plants and watered them from overhead, guaranteeing the spread of disease. Resistant plants were chosen for further crosses and recrosses.

During the early 1990s, he began realizing success. The new varieties were well received locally, but the first half of the decade resulted in nothing Radler deemed fit to enter into the All-America Rose trials. Then, in 1996, he believed he had a winner on his hands and entered a variety labeled Radrazz (new varieties don't have common names until they prove worthy of introduction to commerce) for the mandatory two-year trial period.

I served as the official judge of one of 22 All-America Rose Selections test gardens during the time, so I was sent four plants of Radrazz to judge for myself. I will never forget that early Petaluma morning when I spotted its first clusters of small flowers. I knelt at the base of the bush to determine if what I was seeing was from rootstock, the rose variety onto which hybrids are grafted. Rootstock is intended to remain underground and form sturdy roots for the comparatively weak hybrid budded above. If rootstock growth sprouts above ground and flowers are allowed to bloom, they're usually unattractive, often downright ugly. I wrote a comment to this effect on my score sheet and gave it a zero for novelty. While the plants hadn't a speck of disease in sight, neither did the vast majority of the bushes from other test varieties. I was unimpressed. Judges in the other All-America Rose gardens spread across the country thought otherwise, however, and the new variety, now named 'Knockout,' ushered in the millennium as a 2000 All-America rose in the shrub division.

Rosarians along the Eastern Seaboard went gaga over 'Knockout.' "We'd grow it for its adamant resistance to black spot, if for no other reason," they said. When I asked if they weren't put off by the color of the bloom, which I labeled Pepto-Bismol pink, they assured me that if I were plagued by persistent black spot the way they are, I'd grow it, too. I don't buy that, but I respect their willingness to overlook garish blooms in favor of disease resistance. Still, 'Knockout' tests my limits.

'Knockout' outdid itself in commerce, too, though sales weren't stellar during the first year after introduction, probably because rosarians had grown weary of empty promises of disease resistance from rose suppliers. But word of mouth spread quickly, and by the 2005 rose season, 3.5 million bare-root bushes of 'Knockout' were sold, and it's never looked back - steadily proving it meant business not only when it came to resisting disease but also by dominating sales during forthcoming bare-root rose seasons, thereby pushing some worthwhile roses aside.

Radler was nowhere near done with his breeding efforts, and a slew of his varieties are now available. Although they don't all match the outstanding merits of their famous forerunner, they're at least more nicely colored, especially 'Rainbow Knockout,' another shrub with masses of single flowers, this time in shades of coral, pink and yellow. I would urge Bay Area gardeners to familiarize themselves with Radler roses, but not rush to buy them.

Always keep in mind that we garden in a virtual heaven as far as roses are concerned. Yes, we have mildew, but it's not that difficult to prevent. As for black spot, I've never seen a serious infestation locally, and sustained deep freezes are out of the question. If you worry about rose disease, consider a rose such as 'Julia Child,' another All-America fuss-free rose that has no more time for disease than Julia herself had for margarine. Similarly, if you like pink, consider 'Gemini,' a stunning rose in heart-stopping shades of soft pink, coral and cream. Your best bet for success would be to contact a rose society as close to where you garden as possible and request its printed guide of local star performers. Disease resistance is a vital factor in such rankings.

In December, I flew to my home state of Louisiana for the holidays and stayed with my niece who lives in Amite, a tiny town an hour north of New Orleans. On the drive home, she told me that I was going to be proud of her because she finally grew roses. (Her previous attempts had failed miserably, primarily because of Louisiana's infestations of black spot, often severe enough to defoliate entire plants.)

"I bought four bushes of a rose said to be unusually healthy, but I can't remember its name." Then she said it was decidedly pink, narrowing the possibilities to some number well into the thousands. "The ID tags are still on the bushes," she assured me, "so you can look at them in the morning."

Because of the abrupt time change, I was the first up the next morning. I took a cup of coffee to the front stoop and skidded to a halt when I spotted her rosebushes. The plants looked healthy, all right, but because early winter had been exceptionally warm, there were still flowers in evidence. I would have bet and given odds that I knew what they were, but stooped to read their tag anyway. Sure enough - 'Knockout.'

It was a punch too close to home to suit me.