Answer: It is best to plant them as early as possible so they have more time to become rooted before the ground freezes for winter. (Ideally you would purchase and plant mums in the spring.)
In the fall you can shear off the faded blooms if you wish, or leave them alone. After frosts have killed the foliage you can trim the plant off to about six inches if you wish, or leave it intact. In late fall, mulch around the plant but not over top of it.
Early every spring, cut the plant back very short, as short as you can. When you cut, be careful not to damage new growth coming up from the roots around the perimeter of the plant. Good luck with your mums!
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