Common Ragweed, Annual Ragweed, Annual Bur-Sage

Ambrosia artemisiifolia

am-BRO-zhuh  ar-te-miz-ee-eye-FOH-lee-uh

Synonyms of Ambrosia artemisiifolia (22) (Updated on 11-29-23 from Plants of the World Online): Ambrosia artemisiifolia subsp. diversifolia Piper (1906), Ambrosia artemisiifolia var. diversifolia Piper (1906), Ambrosia artemisiifolia var. elatior (L.) Descourt. (1821), Ambrosia artemisiifolia f. gracilissima D.Cîrțu & M.Cîrțu (1972), Ambrosia artemisiifolia var. jamaicensis Griseb. (1861), Ambrosia artemisiifolia var. octocornis Kuntze (1891), Ambrosia artemisiifolia var. paniculata Blank. (1907), Ambrosia artemisiifolia var. quadricornis Kuntze (1891), Ambrosia artemisiifolia f. villosa Fernald & Griscom (1935), Ambrosia chilensis Hook. & Arn. (1841), Ambrosia diversifolia Rydb. (1922), Ambrosia elata Salisb. (1796), Ambrosia elatior L. (1753), Ambrosia elatior var. artemisiifolia (L.) Farw.(1913), Ambrosia elatior f. aurea Priszter (1985), Ambrosia elatior var. heterophylla Farw. (1913), Ambrosia glandulosa Scheele (1849), Ambrosia monophylla (Walter) Rydb. (1922), Ambrosia paniculata Michx. (1803)(nom. superfl.), Ambrosia senegalensis DC. (1836), Ambrosia umbellata Moench (1802), Iva monophylla Walter (1788)

Ambrosia artemisiifolia L. is the accepted name for the Common 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.

As of 11-19-22 when this page was last updated, Plants of the World Online lists 46 species in the Ambrosia genus. It is a member of the plant family Asteraceae with 1,702 genera. Those numbers could change as updates are made on POWO. 

The distribution map above for Ambrosia artemisiifolia is from Plants of the World Online. Areas in green are where the species is native and purple is where it has been introduced. The map on the USD Plants Database for North America is similar and also includes South Dakota.

The map on iNaturalist shows where members have made observations. Anyone can join and it is a great website to confirm and share your observations. The maps on iNaturalist are continually updated as members post new observations.

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 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 hay fever, it has allelopathic properties that can inhibit the growth and development of surrounding plants.

Writing descriptions in layman’s terms can be complicated but I will give it a shot… There are several links at the bottom of the page to websites with more technical descriptions.

The leaves of the Common Ragweed are, as the name implies, raggy. 🙂 The leaves grow up to 6″ long x 4″ wide in an opposite pattern toward the base of the plant and alternate toward the stem tips. The leaves are deeply pinnatifid with broadly lanceolate to ovate segments…

They say a photo is worth a thousand words… The above photo shows how the flowers appear at the tip of the stems (terminal).

The above photo shows where a branch is emerging from a leaf node…

Stems can be green, reddish, or a combination of both…

<<<<2021>>>

The above photo and the next 7 were taken along the edge of the south hayfield on July 17 in 2021. They are much better…

The Common Ragweed grows in sort of a tree-like shape that branches out more toward the upper half of the plant. Plants can grow 3-4′ tall, more or less, and can form good-sized colonies.

The stems have a combination of long and short hairs (pubescent).

The above photo is a good example of how the plant branches out at the leaf nodes. The branches terminate with flowers…

Hmmm… The stems can be green or a maroonish color. Oh, already mentioned that…

Older stems appear ribbed with shorter hairs…

Missouri Plants describes the leaves as being 2-3 times pinnately lobed with more than 5 primary lobes. As you can tell, the leaves emerge with a long petiole (leaf stem) and the overall outline of the leaf is basically broadly ovate. The leaf segments are lance-shaped in outline and taper to a blunt point…

I haven’t taken good photos of the flowers yet, but I will describe them anyway. The stems terminate with weird flower spikes with separate male (staminate) and female (pistillate) flower heads. That is as far as I go without good close-ups. 🙂

The above photo was taken of a small colony close to the barn on September 24 in 2021. It was kind of a windy day so I couldn’t get good close-ups…

I live on a small farm in Windsor, Missouri where I enjoy gardening, collecting plants, and identifying wildflowers. The farm is in Pettis County but Henry County is across the street, and Benton and Johnson aren’t far away. I have grown over 500 different plants and identified over 250 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 thebelmontrooster@yahoo.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)
TROPICOS (GENUS/SPECIES)
FLORA OF MISSOURI (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
FLORA OF NORTH AMERICA (GENUS/SPECIES)
WIKIPEDIA (GENUS/SPECIES)
USDA PLANTS DATABASE
DAVE’S GARDEN
MISSOURI PLANTS
MSU-MIDWEST WEEDS AND WILDFLOWERS
iNATURALIST
WILDFLOWER SEARCH
ILLINOIS WILDFLOWERS
MINNESOTA WILDFLOWERS
KANSAS WILDFLOWERS AND GRASSES
IOWA PLANTS
UNIVERSITY OF NORTH CAROLINA 
PFAF(PLANTS FOR A FUTURE)
GO BOTANY
LADY BIRD JOHNSON WILDFLOWER CENTER
FLORA FINDER
FRIENDS OF THE WILDFLOWER GARDEN
LEWIS GINTER BOTANICAL GARDEN

NOTE: The data (figures, maps, accepted names, etc.) may not match on these websites. It depends on when and how they make updates and when their sources make updates. 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. Some of the links may use a name that is a synonym on other sites. In my opinion, Plants of the World Online by Kew is one of the most reliable and up-to-date plant databases and they make updates regularly. I make updates “at least” once a year and when I write new pages or add new photos, but I do get behind. We are all a work in progress. 🙂