A window box is a container for growing plants immediately below a window on the outside of a building. It may be removable or be a permanent architectural feature. Window boxes are frequently used on private homes, public buildings, and commercial buildings, and may add considerable beauty and interest, when tastefully planted and successfully managed, not only to the building but to the immediate environment. They have been in use, especially in Europe, for hundreds of years.
The structure of window boxes varies greatly. They may be made of durable moisture and acid-resistant woods, such as redwood, teakwood, cypress, or pine of good quality treated with non-creosote wood preservative. Metal, fiberglass, or cement may also be used for detachable window boxes, and any building material may be used for permanent containers. A typical removable window box has the following inside dimensions: 10 inches wide at the top; 8 inches wide at the base; and 8 inches deep. Most window boxes are as long as the width of the window they are made to adorn, but, for convenience, sections should not exceed 4 feet. Good insulation and drainage are essential.
Plants may be set directly in good soil, or potted plants may be set in damp peat moss or other water-retaining substances. In sunny exposures, petunias, geraniums, lobelia, heliotrope, and lantana are among the most successful. In locations with partial shade, wax begonias, coleus, fuchsias, tuberous begonias, or caladiums may be successful. English ivy, periwinkle, and grape ivy are often used to trail over the edge.