This plant is rated hardy in zones 5-9. Once source I checked stated zones 4-9. My guess is that it needs a cold period during dormancy to trigger new flowers; that rules out bringing it inside unless you have a partially heated garage. Plants only live 3-4 years. A better bet is to take stem cuttings and propagate them over winter to set out as new plants in spring. You could also save seed although it needs special care, as do many native plants. Mix the seed with a small amount of moist sand or potting mix. Put this into a plastic bag which is then placed in the refrigerator for 8 weeks. Thereafter, the seed is sown on top of light seed starting mix; it needs sunlight to germinate. Putting your container(s) in a plastic bag away from direct sun helps keep the seed mix moist. Remove the plastic bag once seeds germinate.
