The mature form of Swampweeds, Stinkweeds emit the same deadly poison in greater quantities.
They are taller than The Kid and spew out toxic gas. It will release the gas when the Kid is close, it is hit, and will release 5-6 gas clouds when killed. The toxic clouds will move outward, lingering for several seconds.
There is another kind that will launch balls of gas at The Kid.
These can be blocked by the Bullhead Shield, but move much faster and can go over terrain, unlike their cloud counterparts.