July seems like an odd time to think about your fall blooming Chrysanthemums. However, you will benefit from pruning and fertilizing them before the middle of this month.
In mid-July, mums form their fall flower buds. The hours of dark that increase as fall comes, trigger the flowering. Pruning them after mid-July reduces the flowers.
Photo: Viceroy butterfly on Chrysanthemums from Texas Aggie-Hort - (Texas A & M Extension) -
a great resource for all things gardening. The main page of their site is here.
When summer pruning your mums, cut just above a leaf node, leaving at least one set of leaves on each stem. Think of the letter Y as a leaf node and snip just above that.
Ohio State University has a fact sheet on mums here.
And the National Chrysanthemum Society has growing tips here.
If your weather does not include rain in for the next two months, be sure to water your mums. They will reward you with fall color when the rest of the garden is beginning to fade.