compass plant or rosinweed, large, coarse North American perennial herb ( Silphium laciniatum ) of the family Asteraceae (aster family), found chiefly in open grasslands. The deeply cut leaves tend to point north and south. It has been used medicinally and is sometimes cultivated. Other plants that have a similar leaf orientation are sometimes called compass plants. Compass plant is classified in the division Magnoliophyta, class Magnoliopsida, order Asterales, family Asteraceae.