I planted chrysanthemums last fall that were in flower.

Hi Arline. You can cut them back in early spring which we are still in and then you should see more growth in the fall.

I keep the bloom buds cut off mine through the summer until around mid-September and then let them go to bloom. If you don't cut the buds off they will bloom in the summer.

Don't cut down because they do it them self. The woody stems you can cut them later

Yes ,once they are about a foot tot feet high you have to cut them in half.this will give you a better flower production for the fall.

I keep them trimmed until about September. Otherwise the become too leggy.

I'm in Texas so have warmer winters than you or any of the other commenters. I've just let mine go, cutting the dead growth off in the early springtime just before, or sometimes along with, the new green sprouts. Amazingly hardy, they are down here.