Flower boxes dress up windows in a living way that is much more striking than any non-organic outdoor window dressing. Planting the boxes with flowers that grow healthy and lush is necessary, as unkempt or unsuccessful flower box plantings can bring down the image of the entire house. Don't limit flower boxes to just window locations. Use them on balconies or long bare expanses of fences or walls to add bright color. As long as the plants receive at least six hours of sunlight, they will thrive where ever you locate the box.
Fill the flower box with a quality potting soil that drains well and isn't heavy. Create your own soil mix by combining 1 part peat moss, 1 part coarse sand and 1 part compost.
Water the soil until it is evenly moist throughout. Add water until it begins to drain from the boxes' bottom drainage holes to ensure the bottom of the soil is also moist.
Plant flower seedlings or transplants into the box to the same depth they were planted in their seedling pots. Space plants half the recommended distance apart, as detailed on the plant label or seed packet.
Plant trailing plants such as lobelia near the edges of the box and bushier plants such as marigold in the center of the box or behind the trailing plants.
Water daily and twice daily during hot and dry weather. Containers dry out faster than garden beds. Check soil moisture before watering and water when the surface of the soil starts to feel dry.
Fertilize flower boxes every two weeks. Use a half-strength solution of a balanced liquid fertilizer. Water thoroughly either during or immediately after fertilizing so the roots can begin soaking up the added nutrients right away.