Eupatorium altissimum (Tall Thoroughwort) on 9-8-18, #504-27.

Tall Thoroughwort, Tall Boneset

Eupatorium altissimum

yoo-puh-TOR-ee-um  al-tiss-ih-mum

Synonyms of Eupatorium altissimum (6) (Updated on 12-1-23 from Plants of the World Online): Eupatorium elatum Salisb, Eupatorium floridanum Raf. ex Torr. & A.Gray, Eupatorium ramosum Mill., Eupatorium rupestre Raf., Eupatorium saltuense Fernald, Uncasia altissima Greene

Eupatorium altissimum L. is the accepted scientific name for the Fall Thoroughwort. The species and genus were both named and described by Carl von Linnaeus in the second edition of Species Plantarum in 1753.

As of 12-1-23 when this page was last updated, Plants of the World Online lists 67 species of Eupatorium. It is a member of the plant family Asteraceae with 1,702 genera. Those numbers could change as updates are made on POWO. The number of genera in the family fluctuates quite often.

Distribution map of Eupatorium altissimum from Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/. Retrieved March 18, 2020.

The above distribution map for Eupatorium altissimum is from Plants of the World Online. Areas in green are where the plant is native. The map shows no other country where the species is native or has been introduced. The map on the USDA Plants Database for North America is the same.

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 and continually updated as members post new observations.

THERE ARE SEVERAL LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING AND BETTER POSITIVE ID.

Eupatorium altissimum (Tall Thoroughwort) on 9-8-18, #504-28.

There are quite a few small colonies of Eupatorium altissimum growing on the farm in Windsor, Missouri in Pettis County (Henry County is across the street). You can find them along back roads, fence rows, and just about anywhere around here. I have identified three species of Eupatorium here on the farm and E. serotinum and E. altissimum were somewhat difficult to tell apart if it weren’t for the leaf petioles (leaf stems). Eupatorium perfoliatum is easy to tell because of its leaves.

Eupatorium altissimum is a perennial plant that typically grows to 3-4 feet tall. The hairy stems are unbranched except for the flowering stems on top. 

I had more photos but I discovered they were Eupatorium serotinum… I will take more photos of Eupatorium altissimum at some point.

The stems can be green or have a purplish tint (Missouri Plants says tan). The fine hairs on the stems give them a powdery appearance.

The top of the flowering stems terminates in kind of a flattish inflorescence with numerous small white flowers. The flowers attract many different insect species.

Its dark green leaves grow in an opposite manner, up to 5” long x 1” wide, and occasionally with teeth along the margins. The leaves are typically lance-shaped, narrowly-ovate, and end at a point. Leaves are also covered with fine hairs (pubescent) making them have a kind of a coarse texture. Leaves feature a prominent midrib with a lateral vein on each side and several veins running toward the margins. The leaves normally have no petioles (sessile) while Eupatorium serotinum has long petioles.

I have enjoyed photographing and learning about the many wildflowers growing on the farm and in other areas. I have grown over 500 different plants and identified over 250 species of wildflowers ( most have pages listed on the right side of the blog). 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 horticulturalist 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. 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.

FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
INTERNATIONAL PLANT NAMES INDEX (GENUS/SPECIES)
TROPICOS (GENUS/SPECIES)
FLORA OF MISSOURI (GENUS/SPECIES)
FLORA OF NORTH AMERICA (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
WIKIPEDIA (GENUS/SPECIES)
MISSOURI BOTANICAL GARDEN
MISSOURI PLANTS
MSU-MIDWEST WEEDS AND WILDFLOWERS
iNATURALIST
WILDFLOWER SEARCH
USDA PLANTS DATABASE
ILLINOIS WILDFLOWERS
MINNESOTA WILDFLOWERS
KANSAS WILDFLOWERS AND GRASSES
GO BOTANY

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. 🙂