Have you ever done/seen this concept?

I live in Central Florida and want to plant my yard with nothing but native plants (to eliminate and/or reduce the amount of watering needed). I live on a semi-busy residential street and people are always out jogging, walking their dogs, etc. I want to plant a ground cover that self-seeds and is a rapid grower (called dune sunflower). My idea was, as I deadhead old blooms, put the heads in baggies and place them in an old mailbox (or something similar) and put a "free seeds" sign on the box so passersby can not only see the plant but also take any available seeds if they would like the same plant in THEIR yard. Would this be weird? Also, would it even be a good idea? I just like it when I go by a neighbors yard and see pretty plants/landscaping and wish I had the same thing for my yard.