Cynthia - the sooner you get them in the ground, the better. You want the roots to become as established as possible before the ground becomes frozen. I can't remember when the first frost starts in MI (been awhile since I lived there), but I would plant them in August. There are some Midwesterners on this forum that can probably give you their planting timeframes, like Tom
@tveguy3.
You chose a nice group of colors for your first order! I hope you enjoy them!