Horse Chestnut Tree leaves are doing their fall furling now, revealing their seed/fruit “capsules,” which look a bit like the ancient spiked ball-and-chain weapon aptly called a flail.
The Horse Chestnut Tree (Aesculus hippocastanum), although fairly common here, is a European introduction named under the questionable belief that its seeds are good for panting and congested horses.
Confusingly, this import often is called a Buckeye Tree, but we have native Buckeye Trees of the genus Aesculus. Both of these chestnut tree species have nutlike seeds that look like a deer’s (buck’s or doe’s) eye. (For Big 10 fans: Ohio State University sports teams are known as “Buckeyes” because Ohio was named the Buckeye State due to the prevalence of its Buckeye Trees when the territory was settled in the late 1700s.)
To add caution to confusion, there also are American Chestnut Trees (Castanea dentata) in a different family that look similar and produce sweet, edible seeds. By the way, don’t try to eat a Horse Chestnut seed; it’s toxic to humans. As for edibility, if there’s doubt, throw the chestnut out or give it to a panting horse. (Images taken in Brooklin, Maine, on September 19 and 20, 2023.)