I've been watching this patch of milkweed for almost two weeks, and today I stopped. There was nice light, only a light wind, and pleasant temperatures so I wandered around a bit trying to get that special spot. I wasn't getting what I wanted, so I decided to pull a few stems and seed heads to bring home. Just as I was pulling the second stem I heard that warning rattle that says "back off now!" The dried grass was thick, and I couldn't get a good look, but what I did see was very large and starting to coil. I swear it wasn't a rattler. Bullsnakes can make a similar noise. Whichever it was though, it wasn't leaving and it was very agitated. Took my plants and walked the long way around back to the car.