Posted: 05/05/2014 at 12:18
It won't divide, and by their nature they're not tidy plants. Some cultivars are more sprawly, some are more upright than others. Miss Jessup's Upright is the most tidy one I know, but it grows quite tall.
Do you know which one you have? If it's one of the sprawly ones you might be fighting a losing battle.
Also they're not long-lived plants. I find the best plan is to take cuttings and replace the plant when it gets too straggly.