Oddly, it's poison to pigs.

Palmer Amaranth may sound like a J.D. Salinger protagonist, but it's actually a nuisance weed spreading across the American south. Also called "pigweed," it's immune to most pesticides. It's incredibly competitive, thriving even in extreme heat and drought conditions. And it's moving north. But here's the thing; this 6 1/2 foot tall plant has a one kilogram edible seed head with more and better protein than whole wheat, while the leaves and stalks are more nutritious than spinach. If I was a farmer, I'd be doing everything I could to keep cotton and soy out of my amaranth fields.