... it was rated with a cold index of 8A. Since then, however, it has proven to be perfectly hardy in zone 7A. The clump in the photograph was planted in 2013 and has reliably returned each spring since.

The one in the photo gets about 3-3.5 feet tall and wide each year. It has proven to be a prolific bloomer throughout the season. It has never been necessary to spray with chemicals.

Good to know, and beautiful plant!, although I find the USDA zone system to be only marginally reliable for predicting plant success. More important is the soil, humidity, wind currents, sun exposure and innumerable other variables of that particular spot. When my arid, high-desert zone is the same as humid sea-level Arkansas (for example), comparisons are almost meaningless.

Add the crazy changing climate patterns and it's a total crap shoot. In my opinion 🙂.

I think the success of that plant is likely due more to your gardening skills than anything else.