Do I cut down this plant in the fall?
Certified GKH Gardening Expert
According to my research, this is a very hardy plant. It is often considered over-bearing. You may cut, chop, and divide this plant as often as you would like.
Here is a link to a few articles on the plants care: https:https://www.gardeningknowhow.com/ornamental/flowers/obedient-plant/