I hope someone with more experience can help me. A few years ago, I bought an Achillea "The Pearl" from a nursery. The blooms were a fully dbl. small white ball. The plant has since died, and I've tried to replace it, but the plants and/or seeds I've gotten since ( all from reputable suppliers) do not look the same-the blooms are not dbl., and the center is yellowish. Also, the new plants do poorly, whereas the first plant was almost invasive. Does anyone know where to get a plant or seeds that will be true? Thanks for any help.