frostweed

(noun) perennial of the eastern United States having early solitary yellow flowers followed by late petalless flowers; so-called because ice crystals form on it during first frosts. Synonyms: frost-weed, frostwort, Helianthemum canadense, Crocanthemum canadense.

(noun) tall perennial herb having clusters of white flowers; the eastern United States. Synonyms: Virginia crownbeard, frost-weed, Verbesina virginica.