Window flower boxes give color to houses and gardens. They are mainly used to create a flower garden in small spaces. The plants in window boxes are typically changed each season to create a year-round decoration. When choosing your window box flowers, pick small young plants that are healthy. These plants adapt better than older, larger plants. Do not choose flower varieties that are tall since they will block your view out the window.
Drill at least eight drainage holes in the bottom of your window box if it does not have adequate drainage. Wash the window box with soapy water and a sponge. Rinse the box with one part bleach and nine parts water. Let the window box air-dry.
Cut a screen mesh that is as large as the bottom of the window box. Place it on the inside of the box. This keeps the soil in the box, but lets the water drain out. Spread a 1-inch layer of perlite in the bottom of the window box to ensure good drainage.
Mix equal parts of peat moss and potting soil to create a lightweight, well-draining soil mix. Spread a 2-inch layer of your soil mixture in the bottom of the window box. Adjust this layer so that the flower seedlings are planted at the proper level.
Remove your seedlings from their containers by pinching the sides of the plant pots and knocking the plant into the palm of your hand. Place the bushy, upright flowers in the back and center of the window box. Pack soil around the roots for support. Plant the flowers close together for a full, dramatic look.
Place the trailing flowers near the edge of the window box so their stems can grow over the rim. Pack soil in between the flowers and fill soil in the spaces where needed. Gently firm the soil down around the plants.
Water the window box until it is soaked. Pour the water into the top until it runs out the bottom. Let the soil drain and settle for two days. Add more soil where it is needed.