I would prune back and root cuttings as suggested earlier. To save over
winter dig up in fall, remove all dirt from roots, hang upside down in
a cool dark place. If place where you want to store isn't dark place
plants in a paper bag. In spring repot, cutback to new growth and they
will grow another season. Have saved plants for many years this way.
Not all survive but most do..

Marv-Montezuma, IA
http://community.webshots.com/user/vmwood