Swaziland's Alien Plants Database

Parthenium hysterophorus L.
ragweed parthenium, parthenium weed, ragweed, Santa Maria feverfew, bitter weed, carrot grass, congress grass, false ragweed, ragweed parthenium, whitetop, demoina weed
Invasive, Major problem species
Origin: Tropical America, Caribbean
Growth Form: Herb
Plant Description: Plant: Annual herb, 0.3–1.5 m high, with an erect, longitudinally grooved stem and deep tap-root; stems and leaves shortly hairy; regular contact with the plant causes allergenic dermatitis and asthma. Leaves: Pale green with some of the hairs containing allergens; rosette and lower stem leaves deeply pinnately lobed, 80–200 mm long; upper stem leaves shorter, less divided. Flowers: White, bisexual, in small compact heads, about 3 mm across, on slender peduncles in a terminal, open panicle, September–May. Fruit: Achenes; seeds black, 2 mm long.
Key Features:
Control: systematic non-selective chemical, pull individual plants by hand, clean vehicles, machinery and animals that come from infested area
More information:
Weeds & Invasive Plants Home Page
NRCS Plants Database


USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada.

Photo - plant

Larry Allain @ USDA-NRCS PLANTS Database

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K Braun, Swaziland's Alien Plants Database

Photo - plants

Rob Mackenzie, Swaziland's Alien Plants Database

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