Bees & butterflies love this plant.
Although given a hardiness rating of 9 (which means that a plant is not very frost-tolerant), this species is thriving in a sunny bed at Kew Botanical Gardens and so should be hardy to at least zone 7. Another report says that it withstands temperatures down to about -40°c when dormant. Yet another report says that it should succeed outdoors in the milder and drier counties, but that it is not very long-lived.