Flower boxes add charm to cottage style houses and a formal look to traditional style houses. Flower boxes on the windows provide an additional way to add color to the front of your house. They are often created by using a combination of perennial plants such as English ivy and geraniums with annuals such as petunia for summer color. Visual interest is created by using taller flowers in the back of the flower box, medium height in the middle and trailing vines over the front edge. There are many flowers to choose from.
Bulb flowers such as intermediate sized bearded iris and daffodils make good background flowers in a window box. They grow from 18 to 24 inches high before they bloom in the spring. Their straight leaves will be hidden by the medium tall flowers planted in front of them. Bulbs need to be divided and replanted every three to four years. Another tall flower is cornflower, which is bright sky blue. Standard size carnations give the flower box an old-fashioned feeling and provide spicy fragrance. Carnations are a perennial that goes dormant but does not die back in the winter. Geraniums do well in flower boxes and they come in a wide range of colors and flower patterns. They are good for a drought tolerant flower box because they bloom well when not over-watered.
Vinca, dwarf zinnia and ganzia are good choices for the middle height range in a flower box. Vinca is a prolific bloomer with white, pink, red or blue five-petaled starlike flowers. Dwarf zinnia gives an instantly sunny look to a flower box with its small multicolored red and yellow blooms. Flower boxes may need more fertilizer and more watering than the rest of the garden. Check moisture levels frequently and use homemade or commercial compost as a fertilizer each month. Other medium height flowers include pansies, salvia and dwarf cosmos. For a window box in a shady spot use impatiens and coleus for strong color.
Ivy trailing from a flower box gives the look of an English cottage garden. Other trailing variety flowers to use for this look include petunias, lantana and lobelia. Petunias come in a wide color range and lobelia have a small white or blue starlike flower. Lantana blooms in globe-shaped clusters of small flowers that are purple, white, orange, yellow, red or blue. Lantana can easily outgrow a window box within three years so prune it back severely each winter to limit growth. Silver bells and nasturtium both grow on long trailing vines and bloom in bright splashes of color. Silver bells is a woody perennial plant that needs pruning each year and gives masses of three-petaled white or lavender flowers.