Box Plant Recommendations: Dimensions and Flowers

Q: What are some hardy window box plants for a balcony that I don’t have to water daily? It’s going to get a lot of sun. What would you recommend for box dimensions and flowers? 

A: I think rosemary, Mexican heather, and dwarf ornamental grass, like ‘Little Bunny’ fountain grass, could withstand the rigors you propose. Calculate one-half cubic foot of soil for each plant you decide on. A window box twelve inches wide, twelve inches deep and thirty-six inches long could hold six plants.