Window flower boxes have widened the scope of container gardening, enabling people to enjoy the sight and aroma of fresh flowers right outside their windows. They not only add color, but are often frequented by birds and butterflies, creating visual interest and enhancing appeal. Make a window flower box for every window of your house or for a few most commonly used rooms. Grow annuals or perennials, and mix tall and cascading flowers for a colorful blend.
Measure your window width and frame, including any trim, to decide the appropriate length and depth of your window flower box. Your window box must fit under your windows, so take the measurement carefully. Ideally, it should be the same length of the window, but you can use two window flower boxes instead of one if your window is very long. A depth of 7 to 9 inches is suitable for most window boxes.
Cut two boards the same size for the front and the back of the window box. Cut two pieces of the same size for the short sides. Cut a fifth board for the base piece that is equal in length to the front and back piece, but equal in width to the two short sides.
Drill ¼ to ½-inch drainage holes, 6 to 8 inches apart, in the base piece.
Hold the back piece and place a short side against it. Check that the joint is flush before attaching the two pieces together with 1-inch galvanized woodscrews. Hold the second short side against the opposite end of the back piece and secure it in place with woodscrews. Hold the front board in place, placing it firmly against the two short sides. Secure it by drilling galvanized woodscrews through both the short sides.
Turn your box over so its base cavity faces upwards, and place the base piece over it so it rests firmly over the edges. Drill woodscrews on each side to firmly attach it to the box.
Smooth out any splinters or sharp edges with sandpaper, and apply paint or primer to the box. Allow it to dry before mounting it outside your window.