What small plants produce seeds quickest?

Dandylions are small plants that produce many seeds fast, and we all love to blow them in the wind, they are pretty weeds, for sure.

A hemp plant can produce enormous amounts of seeds in a short time.

cannabis can produce seeds a couple months after germinating

Any kind of weed. (Not Maryjane). Ever notice how fast and how many can crop up over night?

Kalanchoe daigremontiana :P it's like weed.