Petunia

• Petunia (Petunia x hybrida) is an easy to grow annual that blooms in a variety of colors from spring to frost. The flowers grow well in areas receiving 5 to 6 hours of sun and are well tolerant of heat. Used in hanging window boxes, the plants can trail 3 feet or longer over the growing period. Plant in well-drained, fertile soil for best growth.
  
  

Madagascar Periwinkle

• Madagascar periwinkle (Catharanthus roseus) is an evergreen, perennial with glossy 2- to 3-inch-long leaves. The trailing stems make it an ideal choice for window boxes. The five petaled flowers bloom in shades of pink, purple, red or white. A native of Madagascar, the plant adapts well to poor soil and reseeds itself in loose ground.
  
  

Trailing Lantana

• The Clemson Cooperative Extension lists trailing lantana (Lantana montevidensis) as among the plants well suited for growing in window boxes. The plant blooms consistently and prolifically from spring to frost with purple or white flowers. Trailing lantana grows best in areas of full sun.