Rough Boneset, new to Ohio

A group of botanists explores a very special wet meadow in Athens County yesterday. I met up with Brian Riley, Dan Boone, Dave Minney, Andrew Gibson, Rick Gardner, and Susan Nash for a day of botanizing in southeast Ohio. We had a few targets in mind, and the Numero Uno plant was the white specks in the meadow shown above.

As an aside, this was a sensational field trip for me. I seldom get out on dedicated botanical missions anymore, and only rarely with botanists the caliber of this bunch. I'm always looking at plants everywhere I go, of course, but it is entirely special to be afield with people who know EVERYTHING botanical. Our inner geeks can come out, seldom are common names mentioned, no one looks at you oddly for rattling off scientific names, and I don't think one could find a vascular plant that someone in the group would not know. It was fun engaging in friendly debates over the latest in botanical taxonomy, and catching up in the current state of affairs in the plant world. Dan Boone is always fun to engage with. He loves the obscure genera, and is currently on a dogbane (Apocynum) splitting tear. Go Dan.

The two primary reasons we convened this expedition: Brian Riley, and the plant that he is posing with. Riley, who is an extraordinary field botanist, found Rough Boneset, Eupatorium pilosum, in two off the beaten track Athens County wetlands, and one in nearby Hocking County. I believe Brian found these stations last year, and this was exciting news as this species had never been found in Ohio.

Rough Boneset has a rather spotty and scattered distribution, and occurs south and east of Ohio. It ranges fairly near in Kentucky and West Virginia, and its occurrence here fits with numerous other species of southern plants that reach their northern limits (at least in the interior) in southern Ohio.

A wet meadow full of Rough Boneset. One of the first big questions involving a new botanical find is whether it is native or not. Many plants are introduced to new areas by people, either intentionally or unintentionally. We all felt that Brian's boneset showed no signs of being a likely introduction. The populations were in areas that would not seem likely places for any sort of intentional introduction, and insofar as we know, Rough Boneset is not in cultivation or sold in the nursery trade. The associated plants in each site were natives, and the seep-fed wet meadows that support the boneset seem to be stable plant communities without evidence of any recent disturbance. Of course, it is possible that some natural agents of dispersal such as birds have helped the plants migrate in recent years, and changing climate is abetting its spread. At this point, that would be hard to conclusively demonstrate, however.

The boneset is an eye-catching plant, but it is undoubtedly quite rare and local. If it were in many sites, someone probably would have picked up on it before now. Bonesets and thoroughworts in the genus Eupatorium do have a tendency to look similar, and chances are only a skilled and aware botanist such as Riley would have recognized this species for what it is. Now that he's found it in Ohio, and we have a distinct search image, it'll be interesting to see if anyone turns up additional populations.

Quite a handsome plant, with broad inflorescences of small white flowers, and comparatively small opposite leaves in ramrod straight stems.

The leaves are sessile; they lack petioles (leaf stems). Note the relatively few coarse rounded teeth on the leaf margins. These sorts of details are important in identifying bonesets.

The specific epithet pilosum in the plant's scientific name refers to hairs, which are quite evident on the stem. Long ago, this species was considered a variety of the Round-leaved Thoroughwort, Eupatorium rotundifolium. After seeing Rough-leaved Boneset in the flesh, and knowing Round-leaved Thoroughwort fairly well, I'd say that such a lump was nonsensical and treating them as separate species is appropriate.

I spent quite a while photographing the bonesets, watching an endless parade of insect pollinators come and go. Bonesets provide a bonanza of nectar, and are especially attractive to beetles. Their fluffy clouds of flowers are conducive to insects that are adapted to clambering around the blooms, rather than rapidly flying from plant to plant or hovering before the flowers. Bonesets provide an inordinately valuable contribution to the plant communities to which they belong, when one factors in their importance to insects.

This handsome little beetle is, I believe, a flower beetle in the genus Macrosiagon. A great many were working over the Rough Bonesets. This group of beetles parasitize various bees and wasps, and as such factor into the infinitely complex ecological web of predator and prey. The beetles, of course, are undoubtedly prey for others. Their role in Nature far transcends colorful eye candy at some pretty boneset flowers.

Scads of Pennsylvania Leatherwing beetles, Chauliognathus pennsylvanicus, were feasting on the bonesets. If one were to dock themselves by a patch of these flowers for an hour or so, I imagine the diversity of insect visitors would be fairly startling.

Congratulations to Brian Riley on another in an ever-growing string of fantastic botanical finds. I appreciate him organizing this outing, and inviting me along. I look forward to his next great find.