Parthenium hysterophorus L.

Santa Maria; Feverfew

Herb

Annual

Vascular

Santa Maria Feverfew is an introduced herbaceous annual in the Sunflower family (Asteraceae). It is native to Mexico, Central America, and South America. It has spread to North America, Australia, Africa, India, and other tropical and temperate areas around the world. In Alabama it occurs primarily in the Black Belt region of central Alabama, but can occur anywhere. Santa Maria Feverfew grows in pastures, in fields, along roadsides, on vacant lots, in prairies, and on cedar glades. It is most common in areas where disturbance has occurred. It is an annual with a taproot. Leaves initially form a basal rosette. As the stem elongates, they are alternate. The stem is 1-4 feet in height, branched above the middle, green in color, with distinct ribs. Leaves are petiolate or sessile, ovate to elliptic in outline, 1-2 times pinnately lobed, pubescent, and gland dotted. Flowers are produced in heads. The heads are arranged in open panicles. There are 5-6 very small ray flowers and 12-30 disc flowers per head. The flowers are white. The seed in an achene. Santa Maria Feverfew is a serious invasive species in many parts of the world. It is allelopathic (releases parthenin and other chemicals that inhibit the growth, survival, and reproduction of other plants), toxic to livestock, and causes serious contact dermatitis and allergies in humans and animals.--A. Diamond

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Not Native

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