Horvat treated the walnut frame with Penofin wood finish to make it more durable. Edges were lined with copper flashing to further protect the wood. Then the artist, the homeowner and contractor John Harwood arranged the flora, placing more than 300 1-inch plants — $1 each from Home Depot — inside modular baskets. This mix-and-match process balancing blues and greens and assorted textures proved to be the most difficult part of the project. “We played with it for quite a while,” homeowner Thomas said.