Flowers used in window boxes are particularly effective for adding color and interest to small spaces. To choose the best flowers for your window boxes, determine available sunlight (remember to account for potential shade from your home), what hues will best complement your garden and home, and when you would like your flowers to bloom.
Sweet pea flowers (Lathyrus odoratus), also known as annual sweet peas, are well-suited for use in window boxes, according to the Clemson University Cooperative Extension. Sweet peas display blooms in the following colors: red, mauve, peach, lilac, white, pink and scarlet. With a rapid growth rate, these climbing window box flowers thrive in full sun to partial shade, and prefer cool climates and moist, well-drained soil. Sweet peas reach a height of 4 to 6 feet, according to the NC State University Cooperative Extension. Height is variable depending on whether you plant a bush variety or a climbing vine. The Clemson University Cooperative Extension suggests planting in winter for flowers that bloom in early spring.
Petunias (Petunia hybrida) are suitable as flowers for window boxes. Petunias display blooms in almost any color of the spectrum, but are more commonly found in white, red, purple and yellow hues, according to the Clemson University Cooperative Extension. Petunias bloom all summer long, thrive in full sun to partial shade, and thrive in moist soil (with tolerance to drought). These window box flowers grow to a height of 4 to 12 inches.
Pansies (Viola x wittrockiana) are flowers well-suited for use in window boxes. Pansy plants display flowers in bright varieties of the following colors: yellow, white, blue, pink, purple, orange, lavender, rust, bronze and black, according to the University of Florida IFAS Extension. With a slow growth rate, pansies thrive in partial sun to partial shade, prefer moist soil, and grow to a height of 6 to 12 inches. As explained by the Clemson University Cooperative Extension, pansies bloom from fall through the spring season.
Fuchsia flowers (Fuchsia cultivars) are effectively used in window boxes. Fuchsia plants display blooms in combinations of red, pink, purple, coral and white. Bloom time is spring through summer, according to the Clemson University Cooperative Extension. With a preference for cool temperatures, fuchsia plants thrive in partial to full shade, prefer moist soil, and grow to a height of 1.5 to 3 feet, according to the NC State University Cooperative Extension.