The other day I noticed a TON of these seed capsules littering the ground in a local floodplain forest. They were papery thin, three-lobed, and when shaken the seeds rattled inside. I wanted to find out what plant these capsules came from, so I looked around until I came across some still attached to the plant.
These capsules belong to the American bladdernut (Staphylea trifolia, Staphyleaceae). This woody plant is common in the moist soil of floodplains, which explains the abundance of capsules on the ground in this area.
American bladdernut grows as a large shrub or small tree. It frequently produces adventitious shoots that create dense thickets. You can see the tangled arrangement of shoots in the background of the second photo above.
In the next few weeks the oppositely-arranged leaf buds will grow compound leaves of three (hence the species name S. trifolia). I thought I would try growing some of these from seed, but germination is a bit complicated. The seeds require double cold stratification (two winter cycles) and roughly 18 months before they will sprout.