Deep violet-purple flowers cover a vigorous plant from midsummer to fall. Prune hard each spring and stand back.
Toxic to cats and dogs. The bitter taste usually stops them before they eat much, so serious cases are uncommon.
The sap irritates skin and can raise a rash or blisters on people who react to it. Wear gloves when pruning, and wash your hands afterwards.
For gardeners who like to stay ahead.