I've struggled with a couple window boxes this year. The troubled boxes are under a porch overhang, so they are in heavy shade. I've tried impatiens, coleus, and wax begonia. All end up spindly and bloom-less. Any suggestions for window box plants for deep shade?

Next year I'm thinking of trying ferns, Caladium...not sure what else. It would be nice to have a little color. Thanks in advance for your suggestions!