I don,t know anything about your zone so hopefully someone who does will chime in soon. You don,t need to prune unless it runs out of growing room. When you remove the dead flower heads just remove them to the first set of leaves so you don,t cut off next years flowers. You will probly need to add some winter protection by covering the plant up for the winter( I just stick my pots and all under the house) so you will get blooms next year. Some bloom on old and new wood so that increases your chances of getting blooms if the plant gets zapped by a late freeze. The people who live in your zone can probly tell you how hardie the one you bought is for your area if you post the name.