Giant Ragweed, Wild Hemp, Tall Ambrosia, King’s Head, Crown Weed, Buffalo Weed, Bitter Weed, ETC.
Synonyms of Ambrosia trifida (6) (Updated from Plants of the World Online on 5-2-21): Ambrosia integrifolia Muhl. ex Willd., Ambrosia trifida var. heterophylla Kuntze, Ambrosia trifida f. integrifolia (Muhl.) Fernald, Ambrosia trifida var. integrifolia (Muhl. ex Willd.) Torr. & A.Gray, Ambrosia trifida var. normalis Kuntze, Ambrosia trifida var. polyploidea J.Rousseau. I didn’t update this list of synonyms on the last update because POWO is working on their synonyms.
Ambrosia trifida L. is the correct and accepted name for the Giant Ragweed. Both the genus and species were named and described as such in Carl von Linnaeus in the second volume of the first edition of Species Plantarum in 1753.
Plants of the World Online lists 45 accepted species in the Ambrosia genus (as of 10-17-21-21 when this page was last updated). It is a member of the plant family Asteraceae with 1,677 genera. Those numbers could change as updates are made on POWO. The number of genera fluctuates often.
The above distribution map for Ambrosia trifida is from Plants of the World Online. Areas in green are where the species is native and purple where it has been introduced. The map on the USDA Plants Database for North America (above Mexico) is the same.
THERE ARE SEVERAL LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING AND TO HELP WITH A BETTER POSITIVE ID.
I am not sure I really need to write lengthy descriptions about this all to common weed. It grows on my farm from one end to the other. It is found in every state in the United States, almost all of Canada, and many other countries.
Besides it being one of the major causes of hayfever, it has allelopathic properties that can inhibit the growth and development of surrounding plants.
I am going to write better descriptions soon. I have quite a few wildflower pages to publish, but I wanted to get photos and links at the bottom of the page ready first. If not, it could be next winter before I am able to work on their pages again.
Large colony of Ambrosia trifida along the edge of the south hayfield on 7-17-21.
Ambrosia trifida behind the chicken house on 9-24-21… The roots from the Chinese Elms are above the ground making it impossible to mow in this area…
Same patch of Ambrosia trifida from a different view…
I have enjoyed photographing and learning about the many wildflowers growing on the farm and other areas. My farm is in Windsor, Missouri in Pettis County (Henry County is across the street and Benton and Johnson aren’t far away). I have grown over 500 different plants and identified over 100 species of wildflowers (most have pages listed on the right side of the page). I am not an expert, botanist, or horticulturalist. I just like growing, photographing, and writing about my experience. I rely on several websites for ID and a few horticulturalists I contact if I cannot figure them out. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.
I hope you found this page useful and be sure to check the links below for more information. They were written by experts and provide much more information. Some sites may not be up-to-date but they are always a work in progress. If you can, I would appreciate it if you would click on the “Like” below and leave a comment. It helps us bloggers stay motivated. You can also send an email to me at email@example.com. I would enjoy hearing from you especially if you notice something is a bit whacky.
FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
INTERNATIONAL PLANT NAMES INDEX (GENUS/SPECIES)
FLORA OF NORTH AMERICA (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
USDA PLANTS DATABASE
MSU-MIDWEST WEEDS AND WILDFLOWERS
KANSAS WILDFLOWERS AND GRASSES
PFAF(PLANTS FOR A FUTURE)
LADY BIRD JOHNSON WILDFLOWER CENTER
FRIENDS OF THE WILDFLOWER GARDEN
INVASIVE PLANT ATLAS
TREE OF LIFE WEB PROJECT
NOTE: The figures may not match on these websites. It depends on when and how they make updates and when their sources make updates (and if they update their sources or even read what they say). Some websites have hundreds and even many thousands of species to keep up with. Accepted scientific names change periodically and it can be hard to keep with as well. In my opinion, Plants of the World Online by Kew is the most reliable and up-to-date plant database and they make updates on a regular basis. I make updates at least once a year and when I write new pages and add new photos but I do get behind. We are all a work in progress. 🙂