ellen 
Mums are a fall classic, little puff balls of color, but they don’t necessarily need to be purchased every year. To keep them around year after year, leave the leaves through winter and mulch after the first hard frost to protect the root ball from the cold. Spring growth is a little slow, but once they reach a height of about 6 inches, start pinching a half inch off the stems to create a compact bush. Allow another 6 inches of growth and pinch again. Stop pinching in early July and let the plant develop fully.
The University of Minnesota Extension site offers a guide to hardy varieties that is color and bloom time specific!