Answer: In my experience they do best if they are divided each spring or every other spring, this helps keep them vigorous and allows the gardener to rearrange them. Dig up the clump, separate into sections (cut straight down so each section has new shoots and corresponding roots) and replant at the same depth. Water well as you would any new plant. They can also be propagated by tip cuttings in the spring, each cutting will make a small but blooming plant by fall. Trimming them back once or twice in mid to late spring can help them stay a bit shorter and bushier. Enjoy!
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