Imagine a field of plants that when walked through cuts human skin. Unlike a Stinging Nettle, the leaves would have to have razor-like edges, without the trichome hairs. The leaf edges should cause a finger to bleed if it were lightly dragged across the skin. The plant can be any height, shape, color, etc., but preferably about the size of a sword fern. The razor characteristic also needs to be consistent across seasons (it's not a rare event). 

How would these plants achieve their sharpness? Would metals absorb through the soil accumulate in the leaves? Could a symbiotic relationship help achieve organic razors?

Bonus points if the plant is sharp enough to potentially kill someone while walking through a field.