Turtleheads grow in U.S. Department of Agriculture plant hardiness zones 3 through 9. Trimming back the plants in fall removes the old seed pods and maintains the plant's shape, which prevents self-seeding and improves the appearance of the sleeping winter garden.

Do you cut back turtlehead?

Pruning Turtlehead

If your plants start to get floppy, prune or pinch back the stems of established plants in mid-spring—this will cause the plant to become more compact, but fuller and showier. Since turtlehead blooms late in the season, there is no reason to deadhead spent flowers.

What perennials should not be cut back in the fall?

Don't cut back marginally hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum).