Answer: The Achillea millefolium types tend to sprawl, especially if grown in less than full sun all day long or if grown in moist or rich soil or overfertilized. There are some different "lookalike" types, too, so you might ask your neighbor for some of theirs next time they divide it. A. "Moonbeam" on the other hand is a more upright grower with a distinct crown, and dopes not spread out the way the millefoliums do.
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