ACHILLEA. Both for borders and the rockery the achillea or milfoil (q.v.) is useful. millefolium, ptarmica and tournefortii are three good species for borders. The most popular is the ouble Pearl, producing white flowers in summer and much esteemed for cutting. For rockeries the best are the white-flowering clavcnnae and tomentosa. The achilleas can be raised from seed, and thrive in plain soil. Pron. Ak-i-lec’-a.