Canadian wood nettle (Laportea canadensis, Urticaceae) is a common herb in a floodplain forest I frequently visit near Blissfield, Michigan. It’s often found in wet wooded areas throughout eastern North America.
I wrote about the wood nettle here a couple of years ago when they were flowering in August. This past September these plants instead bore the result of the wind-pollinated flowers; vast arrays of dark seeds in circular arrangements.
The fine white hairs in the photo above are siliceous trichomes. When disturbed they break off and release chemicals that are irritating to the skin, leading to mild contact dermatitis. While not as severe as that caused by stinging nettle (Urtica dioica, Urticaceae), it’s still somewhat unpleasant in large doses.