Answer: Well, that's kind of a tough question. You should always "dead-head" (pick off the spent blossoms) your perennials (as well as annuals). That will help them put energy into the plant instead of trying to generate seed. If you have a late blooming perennial like asters and chrysanthemums, you can (and should) trim them down very early in their growing season. This will generate a fuller, shrubbier growth habit. However, for early bloomers if you cut them back too early you'll cut off their flower buds. With them, you can trim them back after flowering and hope for a second round of bloom. If you don't get that second round, at least you'll have a "shrubbier" plant.
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