The Encyclopedia Americana (1920)/Hardhack

HARDHACK, or STEEPLE-BUSH, an erect species of American Spiræa (S. tomentosa), common in pastures and low grounds, and celebrated for its astringent properties, which cause it to be used medicinally. It is distinguishable by the dense woolly tomentum, which covers its stem and the underside of its leaves; and bears in late summer “a compact, steeple-shaped panicle of peach-blow pink.”