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Flaigg, Norman G.
Ambrosia trifida L.
Great ragweed, Giant ragweed
USDA Symbol: AMTR
USDA Native Status: L48 (N), CAN (N)
A tall, rough, hairy plant with elongated, terminal clusters of nodding male flower heads above few clusters of female flower heads; some plants with hundreds of heads.
This is the giant among the ragweeds, reaching towering heights and possessing long flower spikes. The pollen of ragweeds is spread by wind rather than by insects. Can be invasive, especially in disturbed areas such as a streambank. Pollen from Great Ragweed contains many antigens that cause hay fever.
Plant CharacteristicsDuration: Annual Habit: Subshrub Fruit: Size Class:
Bloom InformationBloom Color: Green , Brown
Bloom Time: Jun , Jul , Aug , Sep , Oct
, WY Canada: AB
, SK Native Distribution:
Throughout much of North America, except far north. Native Habitat:
Waste places, fields, and roadsides.
Butterflies and Moths of North America (BAMONA)
is a larval host and/or nectar source for:
National Wetland Indicator Status
This information is derived from the U.S. Army Corps of Engineers National Wetland Plant List, Version 3.1
(Lichvar, R.W. 2013. The National Wetland Plant List: 2013 wetland ratings. Phytoneuron 2013-49: 1-241). Click here
for map of regions.
Record Last Modified: 2011-01-23
Research By: TWC Staff