Checklist

KNOW YOUR SUN EXPOSURE. "If you don't know, find out before buying plants," says James Hohmann.

GO DEEP. More room allows for more soil, so a better root system will develop, and, in turn, the plants will need less watering.

THINK DRAINAGE. Make sure the box has drainage holes for the water to escape. Otherwise the plants will rot.

PACK IT IN. "Add as many plants as you can to give the box a full look," says Hohmann. "As long as you have a deep box, the roots will grow down, and plants won’t crowd."