The History of Knock Out Roses


The Knock Out Rose, one of the hardiest, most disease-resistant and prolific breeds of roses ever created, is the culmination of years of selective breeding and testing. More than that, it is the result of a deep appreciation and an abiding passion for the beauty and grace roses possess, and the joy they provide.


While beautiful, roses can be very sensitive plants. They are prone to a litany of diseases and pests. Maintaining the vitality of roses is often ongoing and laborious. Some diseases, such as black spot, are so devastating to roses, it is impossible to grow them in certain areas. For decades, rose breeders and growers have been seeking the holy grail of roses; a plant that is easy to grow, resistant to pests and disease, and beautiful.


From his early years, William Radler was fascinated with roses. He actually spent his allowance money on his first rose when he was 9 years old. He became an avid collector, acquiring hundreds of plants and a deep understanding of rose husbandry in the process, winning many awards for his roses.

Early Beginnings

Having little money, he quickly learned that propagating plants from cuttings or bud grafting was an effective way to increase his collection. He also learned caring for roses was demanding. He sprayed his roses regularly for diseases and pests. Preparing for winter was also a significant undertaking. During this time, Radler began pondering the creation of a rose anyone could grow easily. This thought became a lifelong pursuit. Radler would become a rose breeder.

Selective Breeding

Radler began by assessing traits that a perfect rose should have. He wanted his rose to be cold hardy, allowing it to grow in a broader range of climates. He wanted disease resistance to reduce the need for pesticides. Above all, he wanted it to be beautiful, blooming consistently and often. Creating a new rose required a new form of rose hybrid. Roses with some of the traits Radler was looking for were cross-pollinated. The resulting seeds were then planted and grown. Each year, Radler would evaluate these new plants for the multitude of desirable traits he was seeking. The process was then repeated, year after year.

Innovative Techniques

Radler employed many innovative techniques in identifying traits in newly grown roses. One example involved drying and grinding black-spot infected leaves to a fine powder and applying it to the young plants. Any that eventually exhibited the disease were culled out and only disease-resistant plants were grown to maturity. These would then act as breeding stock for future generations.

Final Product

After 15 years of this process, the Knock Out Rose was born and is today the most disease-resistant rose available. The rose Radler created was eventually sent to The Conard-Pyle Co. for years of extensive testing throughout the country. Once completed, commercial production of the rose began, and it is now available in nurseries, garden centers and home improvement stores nationwide. It is easily one of the best-selling roses today. In 2000, the Knock Out Rose was awarded the All American Rose Selection Award, one of the most prestigious awards in the rose-growing community.


Radler's passion for roses has not waned. He continues to breed roses, seeking new and improved varieties. There is no doubt the Knock Out Rose is only the beginning of Radler's beautiful creations.

Keywords: knockout, rose, breed, disease, resistant

About this Author

In Jacksonville, Fla., Frank Whittemore is a content strategist with over a decade of experience as a hospital corpsman in the U.S. Navy and a licensed paramedic. He has over 15 years experience writing for several Fortune 500 companies. Whittemore writes on topics in medicine, nature, science, technology, the arts, cuisine, travel and sports.