A plant of the genus Bupleurum (family Apiaceae), characterized by perfoliate leaves, especially (more fully "American thoroughwort") B. americanum. Now chiefly North American.

A North American plant bearing large corymbs of numerous white flowers and valued for its tonic properties, Eupatorium perfoliatum (family Asteraceae), having opposite leaves, each pair united at the base so that the stem appears to grow through them (connate-perfoliate). Also: (usually with modifying word) any of various other plants of this genus.