It definitely does help to pinch the Parkers back several times. My Anthony Parkers have been in the ground several years now and I see that they are developing now into more of a 'patch'...some spreading going on. I like that. Yours will grow thicker..they do with a couple of years on them. Some are trial and error for me, some of the ones that thrive for other people go belly-up on me. Once I have two or three of something then I can experiment more with where they want to live...and I can see the difference in response. Every last one of them but the natives wants to live around my one avocado tree with the best exposure and soil and close to the leach lines and septic also..lol..when I ask which ones get to live there, they all jump up and shout, "Me! Me!" I have a madrensis in quite a bit of shade...first one I had and didn't want to lose it, now I have one in partial shade and after seeing the one you have out in the full sun, I'll put one out there also. The Hot Lips that lives in the 'good place' is incredibly vigorous, has not stopped flowering. One that lives further out, in not really great soil has not been flowering, is not lush. Leucantha is good about growing just about anywhere, but there again, the ones over the leach lines are 'better'. The Parkers seem to be good about growing well wherever they are also.