[f. THOROUGH prep. or adv. + WORT, after THOROUGHWAX.] A North American composite plant, Eupatorium perfoliatum, having opposite leaves, each pair united at the base so that the stem appears to grow through them (connate-perfoliate), and large corymbs of numerous white flowers; valued for its tonic properties; also called boneset or crosswort.
1828. in Webster.
1845–50. Mrs. Lincoln, Lect. Bot., 185. Florets tubulous, without rays; as, boneset, or thorough-wort (Eupatorium).
1857. Gray, First Lessons Bot. (1866), 100. Cases of real leaves growing together…, those of the common Thorough-wort, and the upper pairs in Woodbines or Honeysuckles.
1893. F. P. Humphrey, New Eng. Cactus, 27. Aromatic herbs, pennyroyal, thoroughwort, and catnip.
† b. = THOROUGHWAX. Obs. rare–1.
1597. Gerarde, Herbal, Table, Throughwoort and his kinds.
