John, I am not a big fan of Miracle Gro. It's very high in salts and in hot dry weather it can burn the plants. Plants need an inch of water a week. Use a tuna can and measure the water depth after 20 minutes. Do the math. I fertilize my mums in spring with a slow release fertilizer such as Plant Tone. They were beautiful. If you feel the need to fertilize again do so when the buds are forming. I recommend you use a fish emulsion. Never fertilize when the plants are dry or the temperatures rise above 85 degrees. Best time to do this is at sun up. Best And Happy Yardening, Nancy.