Ok, here is an idea and of course it can be expanded on. In my town in one of our parks, once a year, around Arbor Day they plant rows and rows of small tree seedlings/saplings(what ever they are called). This area is pretty much left undisturbed throughout the year, and is right out in public view, many people see this area. It gets mowed and trimmed but not all that well; they cant be mowing down baby trees now can they. Near the end of the year they start digging them up and distributing them.

Now just imagine the headline: Arbor Day Growers Come Back To Huge marijuana Field.