how much epsom salt should you use per bush
When was the last time you had your soil tested? Do you know the pH around your roses?. That would be helpful to know. Would you be applying the Magnesium sulfate to large established roses, or to younger plants? The amount you use will depend on how much magnesium is already in your soil. Your soil condition, sandy or clay based soils and how big or how long a rose has been in the ground also be a factor in how much you should use.