fleabane

(noun) hairy perennial Eurasian herb with yellow daisylike flowers reputed to destroy or drive away fleas. Synonyms: feabane mullet, Pulicaria dysenterica.

(noun) any of several North American plants of the genus Erigeron having daisylike flowers; formerly believed to repel fleas.

(noun) common North American weed with linear leaves and small discoid heads of yellowish flowers; widely naturalized throughout temperate regions; sometimes placed in genus Erigeron. Synonyms: horseweed, Canadian fleabane, Conyza canadensis, Erigeron canadensis.