In the photo below, we have a lovely window box with Vinca Vine spilling in front, four ornamental Kale as fillers and a red thriller plant. It’s important to have all three elements for a stunning planter design: thriller, filler and spiller. The names are pretty self-explanatory.
Vinca Vine is winter hardy in zones 7-11 (check your USDA hardiness zone here) and ornamental Kale is generally hardy in zones 2-11, which covers most of the United States. The USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location.