Love and poison ivy

We live near the local high school, and there's a nice stonewall at the end of our streets. Periodically I see teenage couples sitting on the wall while canoodling. It's not indecent, though it usually looks a bit awkward for them; however, the entire wall is covered with poison ivy. Sometimes when I'm passing by, I'll point this out to them, but other times I just think it's a useful metaphor for teenage love--not without its unexpected costs.