Maybe you can host plant related classes or workshops? Advertise having some kind of inhouse plant consultant that people can talk to about plant issues, what kind of plants they should get, maintenance, etc.

Sorry I am booked up for the near future. I don’t typically work off my scheduled hours, but if you want to book me off hours my price is (double the price). If that doesn’t work for you, I can try to recommend someone else.

Can you share examples of your work?