Achillea millefolium L.
Family - Asteraceae
Stems - To +70cm tall, from rhizomes, herbaceous, lanate, branching in upper half, erect, fragrant when crushed.
Leaves - Alternate, sessile, linear to lanceolate or oblong, twice or ternately pinnatifid, lanate below, sparse lanate above. Basal leaves to +25cm long. Cauline leaves typically to +10cm long, +3cm broad.
Inflorescence - Flat or domed terminal cymose arrangement of flower heads.
Involucre - 5mm tall(long), 3mm in diameter. Phyllaries in 2-3 series, with scarious margins, lanate pubescent, imbricate. Outer phyllaries shorter than inner.
Ray flowers - Ligules typically 5 per flower head, white to pinkish, 5mm long, clawed. Expanded portion of ligule 3mm long, 2-3mm broad, emarginate or shallow 3-toothed at apex. Claw 2mm long, greenish, glandular. Achene flattened. Pappus none.
Disk flowers - Disk to 3mm in diameter. Flowers typically 5-20 per flower head, fertile. Corolla tube to -2mm long, greenish, 5-lobed. Lobes white. Achenes flattened. Pappus none. Receptacle slightly convex, with chaff equaling disk flowers.
Flowering - May - November.
Habitat - Roadsides, railroads, disturbed sites, pastures, fields, prairies.
Origin - Native to the U.S. and Europe.
Other info. - The plant has a strong odor when bruised or crushed.
Photographs taken at Hermes Nursery, Kansas City, Kansas, 07-14-00, and in the Ozark Scenic Riverways, Shannon County, MO., 5-24-03 and 6-16-05 (DETenaglia); also at Matson Hill County Park, St. Charles County, MO, 5-17-2012, and at Shaw Nature Reserve, Franklin County, MO, 5-27-2015 (SRTurner).