I have a number of “Knock Out” roses (planted two years). Plants have developed wild looking stalks, large stalks and thorns. Not producing beautiful blooms. I have been pruning wild stalks back to base, but they keep on coming. Any sprays or actions to suggest?
The Gardener’s Answer
Hi, Harry: The abnormal growth that you described on your roses is an indicator of Rose Rosette Disease. The stems on infected roses turn reddish in color and are thicker with more thorns. The foliage is smaller and the blooms are irregular. This devastating virus enters the plants by microscopic mite that feed on the roses. Once infected, the virus will spread from one rose to the next. Unfortunately, removing infected stems will not get rid of the virus and if the pruners were not sanitized between cuts, this would have helped the spread. Removal is the recommendation for roses with this disease. For a positive diagnosis you can take a sample to the Grayson County Cooperative Extension Service. The horticulture agent will be able to confirm the problem or send it off to the University of Kentucky for diagnosis. Most offices have a drop box outside with instructions for leaving plant material for disease identification purposes. The Grayson county offices are located at 123 Commerce Drive in Leitchfield. The phone number is (270) 259-3492.
Kentucky Living-Ask the Gardener