What would I need to do to be qualified to work with growers in the marijuana industry?

You would need the willingness to work with criminals and to forego any possibility of having a federal security clearance, or possibly any federal job whatsoever, and have to make sure you don't include any friends or family in your conspiracy to commit a federal crime.

Don't work in the pot industry. All you'll be doing is contributing to legally making people lazier and dumber.