Common white yarrow is almost too easy to grow. Be sure to plant it in a clump or where you need tough groundcover on poor soils; never include it in a wildflower mixture. This is because this species, if distributed over a wild meadow, will absolutely dominate it in two years or so. Yarrow is beautiful with deep green foliage and graying white flowers, but it spreads so rapidly it quickly crowds out everything else. Great for a bank that can't be mowed, when you realize it will cover the ground there, even crowding out all other weeds. Obvioulsy, very easy to grow.