There is no standard type of pruning they require. You can shear them back periodically to encourage more bushiness. Since they go dormant in winter I would not think that a shearing at this time is of much benefit. After freezes shut the plant down for winter cut it back to about 6" from the ground and mulch the soil around the base of the plant.
Thanks for the question. Please stop in again soon!
Q&A Library Searching Tips