I think there are a couple flowers that make a window box more interesting. Start with "a thriller," something tall like a spiky cordyline, add a few "spillers," something to trail over the sides, like white bacopa, and add lots of colorful fillers to finish it off. These are a few of my favorites.
Love this idea!
What are your favorite plants for window boxes? Please do share.
I'm on a mission to spruce up the new house and shed.