William Radler, creator of Knock Out, collected strains of black spot from around the country. Tests have shown there are five, distinct types, families, strains (whatever you wish to call them) of black spot in the US, fifteen different ones in the world. He deliberately inoculated his seedlings with the diseases and began selecting for those the least affected by spotting and defoliation. While not "immune" to spotting and foliage loss due to black spot, the Knock Out line of roses is the best we have for the widest area of the country.

Yes, others are working with Knock Out in hopes of mining its improved resistance to the diseases. Others which have shown themselves to be resistant to some of the strains are also being used. And, there is always the hunt for other material which may prove itself even more resistant and successful in providing greater health. But, it's sexual reproduction. Each seedling can inherit greater health against more types of disease...or not, so it takes many seedlings and a lot of time to create, raise and test them.

If sufficient funding could be found, there are also plans to create a test so material from seedlings could be provided and tested in a lab for documentation of resistance to specific strains of black spot, which would eliminate the need to actually plant in areas containing the various types for testing.

A lot is already known about the races of the fungi as well as the two types of resistance. It's how to put those types of resistance to as many strains as possible together in ONE plant that is the question. Until money is available for the seedling resistance lab testing, deliberately infecting your seedlings with all the available types of disease, or planting them in as many locations as possible to expose them to all types are the only ways to actively test for wide spread resistance.

As someone who raises seedling roses, I would LOVE for there to be a test available. Imagine taking your goals and removing them from theory and supposition and being able to document actual resistance to specific strains of fungi. THAT would be worth the price of testing! Kim

History of Knock Out RoseWilliam Radler Develops

Hybrids That Are Knockouts
By STEWART DEMPSEY
From the July 9, 2006 edition of the Milwaukee Journal Sentinel

It is hard to imagine a garden without roses. Their captivating beauty and lore are entwined in the hearts and minds of gardeners everywhere.

So strong is the connection to this flower that gardeners would often spend more time and effort growing their roses than any other flower.

But today, in large part because of one local man’s lifetime work, we can enjoy the beauty of roses with little of the effort once required.

William Radler is responsible for many of the easy-to-grow new roses that are extremely disease-resistant, drought-tolerant and ever-blooming.

In 2000, the All America Rose Selections committee named Radler’s original red Knock Out shrub rose as one of its winners and it quickly became the best-selling new rose on the market. Last year alone, some 3 ½ million Knock Out were sold, a total only this rose can claim.

Radler’s Pink and Blushing Pink (a paler version) Knock Outs followed to equal acclaim. And Radler’s Rainbow Knock Out was just named an All America Rose Selections winner for 2007 and will be available next year.

Radler spent his earliest years living with his family at 7th and Burleigh streets in Milwaukee.

They were living in Whitefish Bay when he bought his first rose at a local A & P store with money he saved from his allowance when he was 9.

His parents warned him that the plant would not survive the winter.

Radler was confident it would, and the following year the plant thrived.

From this early fascination, he developed a lifelong passion to develop and improve upon the rose.

He went on to earn a degree in landscape architecture and served as the director of Boerner Botanic Gardens, all the while working on breeding roses as a hobby.

Hundreds of Roses

He now is a full-time rose breeder.

His 1 ½ acre lot in Greenfield with its hundreds of rose bushes is his laboratory.

In 1992, when he moved to his current home and garden, it was the yard and not the house that drew him to the property. He calls it the Rosarium.

His basement is a facility for developing new roses and an incubation area for seedlings waiting for evaluation and possible inclusion in the outdoor Rosarium.

These roses are tested and evaluated for disease resistance, repeat blooming, winter hardiness, resistance to insects and many other desired qualities.

“I keep on selecting the best and continue crossing and crossing,” he says. “There are five hundred or more rose seedlings in the basement at any given time.”

What does he look for in a rose seedling?

The three most important characteristics at this early stage are breaking, habit and flower.

Breaking is how, when and where the plant naturally sends out additional shoots from the main stem.

Habit is the overall growth pattern of the plant (dense and bushy, or tall and spindly, for example).

Flowers are rated on color, size, petal count and fragrance, among other things.

Initial evaluation is critical, but some characteristics will change once the plant is grown outdoors.

Developing a rose, even for someone with a horticultural background, is not an easy task.

It takes a rare individual with the skills to recognize what he is looking at, and someone with an enormous amount of patience.

At its introduction, Knock Out set the standard for Black Spot resistance and repeat bloom.

This beauty has single, bright flowers all season that seemingly float above dark green, lustrous and disease-free foliage.

Knock Out is winter hardy, and is self-cleaning (no dead flower removal is necessary). Its path to market was long and painstaking for Radler.

“The very first crosses I made were in the 1970s,” he says. “Knock Out first saw the light of day in 1989. Knock Out was the only seed in a hip from a reluctant female.”

It can take years to get the right crosses, and there are so many factors including weather, temperature, viability of seeds and genetic unpredictability that can impede the quest for the perfect rose.

Making it disease-free

To ensure disease resistance, the roses in the Rosarium are inoculated with disease pathogens.

“I encourage disease on the property,” says Radler.

Infected leaves are dried and ground in a blender then spread on the healthy plants when the leaves are wet.

Overhead watering during the growing season guarantees the spread of disease. Resistant plants are easily observed and documented, then used in future crosses.

“In the fall of the year disease and insects are at their peak. Does a rose still look great? It has to look good. That’s what people are looking for,” he says.

The plants are further tested and analyzed by the companies responsible for propagation and commercial sales, such as Conard-Pyle Company/Star, the company testing and producing of many of Radler’s introductions.

This year’s introduction is Bright Eyes. It is an upright, pillar-type shrub rose that also can act as a medium sized climber, suitable for smaller gardens.

Its flowers are a delicious salmon-pink with a lighter central eye. In addition to superior hardiness and disease resistance, Bright Eyes is a repeat bloomer and has a lemon-spicy aroma.

Other recent introductions besides those in the Knock Out series include Carefree Sunshine, and Ramblin’ Red. Some of the roses credited to Radler actually are mutations of his roses.

And what does Radler say of his success?

“I’m overwhelmed,” he says. “I can’t believe this has really happened to me. What started as a hobby for me has resulted in what has been called the most sought-after rose in the country. I’m beyond proud.

“But what’s truly wonderful is that something that has brought such joy to me has also helped gardeners who never thought they could grow roses.”

Dr. Griffith Buck set the stage for Bill Radler's roses. Dr Buck began his rose breeding in the 1950's at Iowa State. Because he didn't have a lot of money to work with, he didn't spray his young roses in their trial beds (actually an old corn field) so he lost many of his young roses to BS. Years later he noticed that his surviving roses had much better disease resistance than other roses & realized that he had created a group of roses with better than average BS resistance.

I was at a meeting where a lady who had worked some with Radler stated that he took Dr. Buck's experience one step further by intentionally exposed his young roses in their trial beds by collecting & scattering leaves from BS infected roses in his trial beds & thus eliminating the ones that came down with BS.

Another rose breeder, Ping Lim, is also introducing a number of disease resistant roses, many are sold as Bailey's "Easy Elegance" roses. At another meeting info was given that Lim plants very BS susceptible roses in his trial gardens & uses them to expose his trial roses to BS & find which ones are resistant. I prefer the Easy Elegance & Dr Buck roses to the Radler/Knock Out roses because they are hardier in my Z4 area.

Another group of roses that are being bred for disease resistance are coming out of Germany and they are called ADR roses for short or "Allgemeine Deutsche Rosenneuheitenprüfung''. Many are sold by Palatine & Pickering & this year even Edmunds has a few. The 2013 AARS winner 'Francis Meilland' is an ADR rose.

Another program that tests existing roses, they're not a breeder, is the Earth Kind program from Texas. They've ID'd about 2 dozen roses but it doesn't help me a lot because they're in a much warmer zone but may be useful to to warm zone gardeners.

Somewhere I have a print-out (ie, you could probably find it online) of Knock-out's genealogy. It makes a 5th generation American look-like a purebred. Everything under the sun has been crossed into that rose.

There are other hybridizers doing work in this area. Kordes in Germany has also done extensive work with disease resistant varieties under the ADR program that wirosarian mentioned. I have two of the Kordes "Fairy Tale" roses (Caramel Fairy Tale and Floral Fairy Tale), and they have been just as resistant as Blushing Knock Out.

There are other colors in the "Knock Out" series, you don't have to limit yourself to the original (I don't like the color of the original). Mr. Radler has continued to work on additional disease resistant varieties. Tom Carruth's "Home Run" has Knock Out as a pollen parent.

Jim Sproul, creator of Star Roses' Eyeconic Series Hulthemia hybrids, has also created Thrive! from Home Run, Baby Love and Marmalade Skies. It's a well mannered, very disease resistant red shrub. From many reports, City of San Francisco is also very disease resistant and one of the parents of Home Run. Kim

Here is a link that might be useful: Thrive! on HMF

What interesting histories! Thanks for putting this info here.

Whimsy is a miniature rose whose parent is a double knock-out. I haven't grown this rose, but I heard that it's disease resistance is similar to a knock-out.

Here is a link that might be useful: HMF - Whimsy

Roseseek--Thrive is lovely! If I didn't already have 3 HomeRuns, I'd get some Thrives!

My only complaint about Home Run is that it is probably the thorniest rose in my garden. It attacks if you even just walk by it!

Kate