My double knockout roses are 3 years old, healthy, and bloom all season. I give them organic fertilizer in the spring. My question is, is it normal for 2/3 of the last years growth to die over the winter? I waited till late May this year to prune the dead branches, hoping they would green up, but every year I lose a lot of old growth. I would like for them to be bigger in subsequent years. Currently, at the end of the season, some are 3 x 3 and others are smaller. One year I wrapped them in burlap but it didn't help.
Knockout Rose Dieback
The die back of rosebushes canes is very normal here in my Colorado rose beds. Some years, like this most recent winter, I have to prune most of my rosebushes down to within an inch or so of the ground. With the use of a good organic based rose food, some kelp meal, Epsom Salts and teas, along with keeping them watered well, they come back very nicely each year. In years where it is very cold, dry and alot of winter winds, the die-back is sure to be more. Those years are also when it is very easy to lose several rosebushes over the winter. The rosebushes need at least a light watering through the winter time on days when we can do so, watering as early as the temps allow us to in the day. That way the water has a chance to get pulled up in the roots before things freeze up again at night. The only way one could save alot of the canes in cold climate gardening is to build some sort of mini greenhouse over each bush for the winter. Even wrapping them with burlap does not prevent the harsh freezing cold temps from getting to them. It helps prevent the winds from getting at them but the cold takes the life out of the canes. As they get established they should come back stronger each year, meaning many more canes and blooms. Some rosebushes do not truly hit their stride until they are 5 years old. Here is a link to an article I wrote about winter rose care prep: https://www.gardeningknowhow.com/ornamental/flowers/roses/roses-winter-care.htm
You may want to give each of the rosebushes some water with root stimulator and a product called super thrive mixed into the water together. It helps get them going well and helps relieve any stresses that may be setting them back.