Using Rain Gardens to Keep Waterways Pollution-Free

This mint produces billowing spikes of blue flowers, a nice contrast to the yellow-flowering plants nearby. Most mints reseed freely, so if you don't want new plants springing up, cut back spent blossoms promptly or plant a sterile kind, such as catmint (N. x faassenii). Blue flowers.

Zone: 3; Hardy everywhere

Height: up to 4 feet.