White Yarrow (Achillea millefolium)
A perennial with leaves finely divided, flowers are white, in dense, flat-topped clusters; plants very aromatic. Quite drought tolerant. Blooms from mid- June through August. Naturalized throughout the U.S., usually in fields and roadsides. Prefers full sun, dry to moist soils; very aggressive with spreading rhizomes, difficult to eradicate. Can be mowed to form a groundcover, good for soil erosion, withstands combination of heat and humidity.