Hey. I need an easy and cheap plant idea and I need it quick. So if you would help me find a fast growing plant thanks. Answered

I would recommend that you visit your local nurseries, since they'll be intimately familiar with your local habitat better than someone say from China, the UK., or even from other Americans that live in different microclimates. (For instance, although I live within a ~500 mile radius of your town, what would grow natively nearby my home would not be local flora for Memphis)

oat grass grows quick, like 7 inches in a week

Beans, Water cress, Mustard, Lawn Grass, - All fast germinating and will do so on wet tissue.

Assuming you are going to grow it from seed....dandelions, nasturtiums, grass, beans

Demonstrate what?

Look around in local gardens.