Ragweed Parthenium (Parthenium Hysterophorus)
Asteraceae (Sunflower Family)
Group: Dicot (Broadleaf)
Erect, annual herb, which forms a basal rosette in the early stage of growth, native of tropical America. It is common along canals, ditch-banks, non-crop areas, and cultivated fields. Ragweed parthenium is often confused with common ragweed.
Seedling leaves are pinnately lobed and form a basal rosette. Leaves and stem will be hairy.
Leaves of mature plants alternate, deeply divided, and hairy. Leaf divisions are sometimes opposite or alternate. Lower leaves form a basal rosette and lobed while upper leaves are entire to slightly lobed. Leaf stalks are very short.
Stem is erect, much branched, ridged, has short hairs (not as hairy as common ragweed), and 1 to 3 feet tall.
Flowers are small, numerous, white, and arranged in clusters at the tip of branches. Seeds are black and topped with two lateral scales (pappus).
