My knockout roses were blooming, but have quit. Do I need to fertilize them?
My Knockout Roses Were Blooming, but Have Quit
If the temps are in the high 90's to 100's where you are the rosebushes could be just taking a break to gain strength back. Heat stress will do this. Sometimes they do take a break between bloom cycles to regain strength. If you have not fertilized them at all or it has been a month or more, then yes fertilize them now. Make sure the soils moisture is good before and after feeding them as well.
Stan the Roseman