The client called requesting information on when to prune and fertilize Knock Out® roses.
DIAGNOSIS / RECOMMENDATION:
The log sheet indicated that according to the VCE Publication A Guide to Successful Pruning: Shrub Pruning Calendar generally roses can be pruned in February – March and/or in July August.  The client was also advised that “[F]ast release fertilizer is applied in early spring or late fall, with slow-release applied any time during growing season.”
The Knock Out® rose is a hybrid rose bush created by rose breeder Willilam Radler through years of experimentation and cross breeding, and was released in 2000. It has become the favorite of homeowners and landscapers because it requires little maintenance, is hardy to Zone 5, and tolerates hot weather better than many other varieties of roses. In addition, it is ‘self-cleaning,’ (the old blossoms drop off after they have faded), and it experiences fewer instances of disease and pest attacks than other roses.   However, recently Rose Rosette Disease has been taking its toll on Knock Out® Roses.  
Knock Out® roses can tolerate a minimum of four hours of sunlight per day, but they will be thin with reduced flowering. They do best in six to eight hours of sunlight per day. In particularly hot and sunny locations a little light shade during the heat of the day can reduce the stress to the plant. 
Knock Out® roses can tolerate dry conditions, but prefer moist, well-drained soil with a pH of 6.0 to 6.5. It is always advisable to have a pH soil sample test done, and if recommended by the test results amend the planting bed soil appropriately prior to installing any new plants.
Plant Knock Out® roses during their dormancy, generally between November and April. Add 2 to 3 inches of mulch around the base of the plants to help keep the soil moist and provide extra nutrients. Because they can grow 3 to 4 feet wide and 3 to 4 feet high they should be planted at least 3 feet apart on center. This will allow for air circulation between established plants. However, it may be advisable to allow more space between each plant to reduce the possibility of any disease being transmitted between plants. 
Even though Knock Out® roses generally grow to roughly 4 feet by 4 feet they can benefit from annual pruning during dormancy – late winter to early spring. Most references advised cutting the canes down to 18 to 24 inches. According to the University of Maryland extension website: “Cutting them back very severely, like a hybrid tea rose, is not recommended. They won’t die but will require a long time to recover. Periodically, older, declining, and broken canes will need to be removed. This can be done at any time of the year.” 
From The Bedford Extension MG Help Desk
Linda E., Bedford Extension Master Gardener Volunteer; Help Desk Coordinator
All resource links accessed June 24, 2017
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Answers provided herein were based on specific situations and growing conditions.These recommendations may or may not be appropriate for all circumstances.For specific recommendations for your particular situation please contact your local Cooperative Extension Office.
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–A Bedford Area Master Gardeners Association (BAMGA) Publication–