Helenium amarum

Helenium amarum, bitterweed or yellow sneezeweed, is an annual herb of the daisy family (Asteraceae) native to the south-central United States from Texas, Oklahoma and Louisiana to Arkansas and New Mexico, and to adjacent northern Mexico; it has spread as a weed across the south-eastern United States and is naturalised in parts of Australia and the West Indies. The plant forms a bushy, much-branched, erect mound 20-70 cm tall, with very narrow, thread-like, linear leaves that give the foliage a feathery look. From early summer through autumn the branches carry numerous long-stalked flower heads, each with eight to ten lemon-yellow, three-lobed ray florets reflexed downward around a near-spherical, golden-yellow disc bearing up to about 250 tiny disc florets. The fruit is a small pubescent achene topped by scarious pappus scales. The whole plant contains the bitter sesquiterpene lactone tenulin, which gives the herb its name and renders it toxic to grazing livestock and capable of imparting a bitter taint to milk.