giant ragweed

(Ambrosia trifida)

Conservation Status
giant ragweed
  IUCN Red List

not listed


N5? - Secure

SNR - Unranked


not listed

Weed Status

County Noxious Weed in Sibley and Waseca Counties.

Wetland Indicator Status
  Great Plains

FAC - Facultative


FAC - Facultative

  Northcentral & Northeast

FAC - Facultative


Giant ragweed plant is easily distinguished from other ragweeds by its large size and palmately-lobed leaves.




2 to 9


Flower Color




Similar Species


The leaves of other ragweeds are pinnatifid (western ragweed) or bipinnatifid (common ragweed).


Moist soil. Disturbed sites, fields, roadsides.




August to September


Pests and Diseases






Distribution Map



2, 3, 4, 5, 7, 28, 29, 30.









  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Asteranae  


Asterales (sunflowers, bellflowers, fanflowers, and allies)  


Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Asteroideae  
  Supertribe Helianthodae  
  Tribe Heliantheae (sunflowers and allies)  
  Subtribe Ambrosiinae (cockleburs, ragweeds, and wild quinines)  
  Genus Ambrosia (ragweeds)  

Subordinate Taxa






Ambrosia trifida var. integrifolia

Ambrosia trifida var. trifida


Common Names


giant ragweed

great ragweed














Palmately Lobed

Similar to a hand. Having more than three lobes that radiate from a single point at the base of the leaf.



Deeply cut, more than half way to the midrib but not to the midrib, into lobes that are spaced out along the midrib; the lobes do not form separate leaflets.

Visitor Photos

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    giant ragweed   giant ragweed  
    giant ragweed   giant ragweed  


    giant ragweed   giant ragweed  

Flower Heads

    giant ragweed      


    giant ragweed   giant ragweed  

Early Spring

    giant ragweed   giant ragweed  



Ambrosia trifida GIANT RAGWEED
Frank Mayfield
  Ambrosia trifida GIANT RAGWEED  



Visitor Videos

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Other Videos
  Giant Ragweed - University of Missouri
MU Plant Sciences

Uploaded on Feb 28, 2012

Giant Ragweed, MU Weed Science, University of Missouri

  Greenhouse Giant Ragweed .m4v
Ohio State University Weed Science

Uploaded on Feb 22, 2012

Dr. Mark Loux from The Ohio State University talks about herbicide resistant giant ragweed research being done in the university greenhouses.

  Weed of the Week #790 - Giant Ragweed (Air Date 5/26/13)

Published on Jun 4, 2013

It's our Weed of the Week, Giant Ragweed.




Visitor Sightings

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Location: Wyoming

I have one about 5 foot tall in northern Wyoming. 

  Terry Pfleghaar

Location: Elk River, MN

I allowed this to grow in my garden, not knowing what it was. I finally was able to identify it when it was about 10’ tall!


Baker Park Reserve

Bertram Chain of Lakes Regional Park

Blaine Preserve SNA

Blue Mounds State Park

Bur Oak WMA

Carpenter St. Croix Valley Nature Center

Carver Highlands WMA, South Unit

Carver Park Reserve

Cedar Mountain SNA

Cedar Rock SNA

Cherry Grove Blind Valley SNA

Clifton E. French Regional Park

Compass Prairie SNA

Cottonwood River Prairie SNA

Crosby Farm Regional Park

Crow-Hassan Park Reserve

Des Moines River SNA

Dodge Nature Center

Elm Creek Park Reserve

Falls Creek SNA

Felton WMA

Forestville/Mystery Cave State Park

Franconia Bluffs SNA

Frontenac State Park

Glacial Lakes State Park

Glynn Prairie SNA

Great River Bluffs State Park

Hastings SNA

Hayes Lake State Park

Holthe Prairie SNA

Hyland Lake Park Reserve

Hythecker Prairie SNA

Iron Horse Prairie SNA

John Murtaugh Memorial WMA

John Peter Hoffman Spring Brook Valley WMA

Joseph A. Tauer Prairie SNA

Kasota Prairie SNA

Kellogg Weaver Dunes SNA, Kellogg Weaver Unit

Kilen Woods State Park

King’s and Queen’s Bluff SNA

Laible Woods

Lake Louise State Park

Lake Rebecca Park Reserve

Lebanon Hills Regional Park

Lost Valley Prairie SNA

Lundblad Prairie SNA

Malmberg Prairie SNA

Mary Schmidt Crawford Woods SNA

McKnight Prairie

Minneopa State Park

Minnesota Valley NWR, Louisville Swamp Unit

Minnesota Valley NWR, Rapids Lake Unit

Minnesota Valley NWR, Wilkie Unit

Minnesota Valley State Recreation Area, Lawrence Unit

Morton Outcrops SNA

Mound Prairie SNA

Mound Spring Prairie SNA, North Unit

Myre-Big Island State Park

Northern Tallgrass Prairie NWR, Spieker Unit

Ordway Prairie

Oronoco Prairie SNA

Osmundson Prairie SNA

Oxbow Park & Zollman Zoo

Partch Woods SNA

Pine Bend Bluffs SNA

Prairie Coteau SNA

Prairie Creek WMA, Koester Prairie Unit

Racine Prairie SNA

Red Rock Prairie

Rice Lake State Park

River Terrace Prairie SNA

River Warren Outcrops SNA

Robert Ney Memorial Park Reserve

Rock Ridge Prairie SNA

Rockville County Park

Rushford Sand Barrens SNA

St. Croix Savanna SNA

Sandpiper Prairie SNA

Savage Fen SNA

Schaefer Prairie

Seminary Fen SNA

Seven Springs WMA

Shooting Star Prairie SNA

Split Rock Creek State Park

Spring Lake Park Reserve

Swedes Forest SNA

Tiedemann WMA

Tympanuchus Prairie

Uncas Dunes SNA

Upper Sioux Agency State Park

Vermillion River WMA

Wahpeton Prairie WMA

Western Prairie SNA

Whitetail Woods Regional Park

Whitewater State Park

Wild Indigo SNA

Woodbury WMA

Yellow Bank Hills SNA







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