I don't have a green thumb, per say, but, I have on occasion had the need to go to Walter Andersen's Nursery. They have rows and rows and rows of different types of flowers to be grown in pots or other planters or in flower beds. Walter's also has beginnings of shrubs and trees that one can plant and watch grow into areas of privacy or just splendid trees for nature.
The nursery also has gardening tools, fertilizers, plant treatments for the gardeners. There also are supplies for all of the garden pests-- snails, slugs, moles and other rodents. There also is a wide variety of plant holders, plant supports, bird baths and other decoratory items to place in the garden to enhance it.