This paragraph is for Sam, who suggested today's plant. He is a chemistry teacher. The active chemical in poison sumac, ivy, and oak is urushiol. It causes more severe rashes from poison sumac than from poison ivy or oak. The difference is the molecule's side chain. In poison sumac it has 13 carbon atoms, in the others it has 15 or 17.
Poison sumac is an indicator plant. Indicators are plants so dedicated to habitats that you can identify the habitat by the plant. But around here this is an indicator of rattlesnakes. It's also the host for rare Mitchell's satyr butterfly caterpilars. The wood is beautiful, with yellow sapwood, and redbrown heartwood. Too bad we can't use it. The largest poison sumac is 30 feet tall, with an 18 inch circumference.
Barb says I have a lot of strange junk in my head. In my subconcious too. In Viet Nam, we ate fruit that looked like pears, tasted like strawberries, and had a strange external bean-shaped seed hanging from the bottom. We were getting itchy rashes, particularly around our mouths. One night I dreamed that the fruit was cashew. I must have seen it long ago, but had no concious memory. I first ate cashew nuts in Sri Lanka when I was ten. Cashew is in the same family as poison ivy and sumac, and causes the same problems. But it tastes better than C-rations!