While I was weeding today, I was stung by a plant. I'll do my best to describe what I believe to be the culprit. It is about 3' tall, and doesn't have a whole lot of leaves left. From what I can tell, the leaves are narrow. The stem is hairy, as is the stem that attaches the leaves to the plant. The top part is branched, with each branch ending in a whole bunch of seed pods, about 2 mm in size. The seeds are attached to tiny tan colored hairy things, and it is either the seed or the hair that I believe to be responsible.

There is a strong correlation between where these little seeds fell on my hand, and where it hurts. It feels like pin pricks, and hurt like mad when I washed my hands.