My "Knockout" rose bush has not bloomed in 4 years. What do I need to do to get it to bloom?
Did you fertilize it?
You need to prune the rose bushes by their stems to make them bloom properly. Also, you should not plant the rose bushes very close to each other because they need good air circulation for blooming.
When they finish blooming, you need to cut off the dead heads (rosehips). Cut each branch back to where you find the first set of 5 leaves. And fertilize like MLY said.
maybe it is just the lack of sunshine. if you expose it more to sunshine, it might bloom.
Proper pruning and sunlight helps.
Mix up some epsom salt water and water them. This is assuming you are already pruning and dead-heading properly.