Late Boneset, Late Thoroughwort
Eupatorium serotinum Michx. is the correct and accepted scientific name for the Late Boneset. It was named and described as such by André Michaux in Flora Boreali-Americana (Michaux) in 1803.
The genus, Eupatorium L., was named and described as such by Carl von Linnaeus in the second edition of the first volume of Species Plantarum in 1753
As of 1-17-22 when this page was last updated, Plants of the World Online lists 61 accepted species in the Eupatorium genus. It is a member of the plant family Asteraceae with a total of 1,677 genera. Those numbers are likely to change as updates are made on POWO. The number of genera in this family fluctuates quite often.
The distribution map above of Eupatorium serotinum is from Plants of the World Online. Areas in green are where it is native and purple where it has been introduced. The map on the USDA Plants Database for North America is similar.
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 took the above photo of the Eupatorium serotinum in the pasture next to my backyard. Of course, there are several small colonies here and there but this one was quite handy. 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 serotinum is a herbaceous perennial that is quite common from the central part of the U.S. eastward and Northeast Mexico where it is native. The Missouri Plants says is the most common and weediest of Missouri thoroughworts.
Eupatorium serotinum can be found in prairies, pastures, glade margins, savannas. pond margins, bluffs, gardens, along railroads, along back roads and highways, moist areas near ponds, streams, and rivers. Some sites say it prefers moist loamy soil while others say it has little habitat preference and will grow just about anywhere. Here on my farm, I have found it near the ponds and southeast corner where it is low, but also where the soil is dryer. I will admit, the plants look much better where the soil is damper.
Some of the photos were taken in 2019 and some in 2021… They are not in order. 🙂
Eupatorium serotinum has a fibrous root system with spreading rhizomes. New stems grow from the rhizomes as with many perennial wildflowers.
The stems of Eupatorium serotinum I have seen on the farm are a purplish color, but they can also be a greenish tan. The stems have small white hairs (pubescent) giving them a chalky appearance.
The above photo also shows where side branches emerge above the leaf petioles at the nodes
The above photo was taken of a plant that was growing in the pasture next to the backyard on 8-30-19. You can see the main stem is ridged… Notice the petioles of the leaves hanging downward…
The leaves mainly grow in an opposite manner along the stems but can be alternate at the upper nodes. They can be up to 7” long x 2 1/2” wide with long petioles (leaf stems). The long petioles distinguish them from other Eupatorium species found in Missouri. The leaves are narrowly lanceolate to ovate, pointed at the tip, and usually coarsely toothed or serrated. The upper leaf surface is either smooth (glaucous) or moderately hairy (pubescent).
The lower surface is more densely hairy. Leaves have 3-5 distinct veins (usually 3) that grow from the base of the leaves. I have only seen leaves with 3 veins but I haven’t looked at that many…
The stems produce several clusters of leaves (fascicles) that are smaller than the other stem leaves.
The flowers of Eupatorium serotinum are similar to the other two Eupatorium sp. on my farm. The branches terminate with a flat-topped cluster of discoid flower heads that have no ray florets (petals). Flowers contain 9-15 disc florets (sometimes more) with 5-lobed corollas. The long divided styles stick out giving the flower a feathery appearance. The flowers also have black anther tubes which may give them a grayish appearance at a distance.
I haven’t taken good flower photos for this species yet, especially close-ups. The wind was blowing when I was taking the photos for this page in 2021 so any flower photos were blurry. My thanks to Bioimages for allowing people to use their photos for educational purposes. I will replace it when I take suitable photos…
The small black achenes (seeds) have flat tufts of hair that allow them to fly through the air.
I have enjoyed photographing and learning about the many wildflowers growing on the farm and other areas. I have grown over 500 different plants and identified over 200 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 firstname.lastname@example.org. I would enjoy hearing from you.
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)
MSU-MIDWEST WEEDS AND WILDFLOWERS
USDA PLANTS DATABASE
LADY BIRD JOHNSON WILDFLOWER CENTER
KANSAS WILDFLOWERS AND GRASSES
NATIONAL WILDLIFE FEDERATION
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 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 or add new photos but I do get behind. We are all a work in progress. 🙂