KNOCK OUT® roses were bred to be disease resistant.
William Radler, a Wisconsin rose breeder, introduced the first KNOCK OUT® rose in 2000 and it immediately became an All American Award winner. Mr. Radler wanted his roses to be lower maintenance than any other rose so he experimented with growing roses that were the most hardy, disease and pest resistant.
He was successful with KNOCK OUT® roses and they were immediately popular with a quarter of a million rose plants sold in the first year. Many people, especially beginner rose gardeners think that if a rose is disease resistant, it can never acquire a disease. This is not true. Being disease resistant doesn’t forever protect a plant from disease, it just means it has been bred to strongly resist the disease.
The KNOCK OUT® roses were bred to be cold hardy and resistant to several diseases, especially blackspot. Blackspot is a fungus which grows on roses and other plants. As you might expect, the leaves do develop black spots and will eventually turn yellow and fall to the ground. Some plants eventually die.
If you should have a particularly rainy summer or planted your roses in a spot that is not well-drained, any rose, even KNOCK OUT® roses can get the blackspot disease. The good thing about this variety of roses is that even though they may acquire blackspot, they will not die. They will, in fact, come back the next year. However, if your KNOCK OUT® roses do have blackspot disease, it is best to use a fungicide or alternative treatment to get them healthy again.
Powdery mildew can form on even a disease resistant plant if it doesn’t get enough sun. While the KNOCK OUT® family of roses doesn’t need as much sunlight as other roses, they do need a minimum of around four hours per day. If you plant your roses in a part of the yard that rarely gets sun, even the most disease resistant rose can end up with powdery mildew. The more humid your location is, the more apt your roses are to develop mildew.
The best way to protect your KNOCK OUT® roses from disease is to take good care of them.
While they are low maintenance, that doesn’t mean no maintenance is needed at all. Plant your KNOCK OUT® rose where they will get at least four hours of sun every day and where the soil is not overly wet. Diseases and pests hit the weakest plants so if you go the extra mile in rose care, you can be sure to avoid trouble.
Make certain to add compost to your soil when you plant your roses. A good organic fertilizer will get them off to a good start. Water your roses from underneath and not from above to avoid blackspot. Mulching also helps protect from diseases which can start in the soil and work their way up the base of the plant.
Keep your garden clean at all times because piles of debris and mounds from pruning and weeding can facilitate the growth of both pests and diseases.
If you do have insects, bring in predator insects to eat them. There are also organic sprays and dusts which can protect roses from pests and disease without the use of toxic chemicals.
KNOCK OUT® roses are pest and disease resistant but don’t blame the roses if they are not completely impervious to every disease or every pest. Just giving them good basic care–water, sun, fertilizer, mulch– will keep them healthy and flowering from spring to fall. Prevention is the best pest and disease treatment around.