Answer: Many gardeners will trim these back by about a half or so when the blooms slow down and the plants begin to flop badly and look too unkempt. This will stimulate another strong bloom flush later in the season as long as the plants are sufficiently watered. Generally these are very drought tolerant but if there is an extended summer dry spell you might water them deeply once or twice to help them along. If you don't cut them back they will still bloom off and on but will not be as showy.
Q&A Library Searching Tips