A service pust nutrient applications on all of my shrubs 3 times a year. They call it deep root fertilization. If this is donedo I need to[ or should I] do feedings throughout the year?
Knock Out Roses
You may not need to. I would ask for a breakdown and the NPK rating for their applications. This way you can be sure what they are getting. Giving the rosebushes some kelp meal and alfalfa meal (1/2 cup of each) twice a year would likely be good to do. Work the meal into the soils lightly and water it in. I would apply one then wait a couple weeks and apply the other.