Common Yarrow

Achillea arenicola A. Heller, Muhlenbergia 1: 61. 1904
A stout perennial, with a long creeping rootstock; stem 3-5 dm. high, densely covered by silkyvillous white pubescence; leaves bipinnatifid, densely whitevillous, 5-10 cm. long, usually less than 1 cm. wide, the lower linear-oblanccoIatc in outline; divisions densely crowded and ascending, the ultimate ones ovate or lanceolate, with callous mucronate tips; heads in dense round-topped corymbiform panicles; involucre campanulate, 5-6 mm. high, 4-5 mm. broad; bracts densely villous, 20 or more in 4 scries, the outer ovate, acute, the inner elliptic or oblong, obtuse; margins dark-brown; ray-flowers about 5; ligules white, nearly orbicular. 2.5-3 mm. long; disk-flowers 20 or more; corollas cream-colored, 3 mm. long; achenes 2 mm. long, slightly margined.
Type locality: Sandhills at the upper end of Bodega Bay, Sonoma County, California.
Distribution: Coast and islands of California; apparently also in subalpine situations, Nevada County, California, and on Vancouver Island.