Answer: The sooner you plant them, the better. The reason is that they need as much time as possible to become rooted before the ground freezes for winter.
After the flowers fade you can trim off the dead flowers if you wish. After frost, you can cut the plant back to about six inches. In late fall, mulch around them (but not over top of them) with organic mulch several inches deep. Next spring, cut the stems back as short as you can -- close to the ground.
Once they begin to grow again next spring, you will need to pinch out the growing tips or lightly shear them periodically. This helps them grow dense and bushy with more flowers. Begin when they are three to four inches high and pinch every few weeks until the fourth of July.
Enjoy your mums!
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