Wooden flower boxes form portable gardens that add color, beauty and fragrance outdoor or indoor spots. These container gardens are easy to construct and usually built on-site to fit the particular spot. Depending on personal taste, place a flower box filled with bush, tall or trailing annuals, perennials and biennials on the ground or under a tree, or mount it to a wall or under a windowsill for beauty and interest at varying eye levels.
A square or rectangular flower box is fairly simple to construct, even by a novice. Each box is comprised of five lengths of the selected wood- a base, two long sides and two short ends for a rectangular and four identical lengths for a square one. Secure the lengths to the edges of the base with wood glue followed by rows of galvanized wood screws. For a raised flower box that prevents gardeners from bending too low, secure a wood block at each corner of the base that serve as its "legs". Glue decorative molding to the upper edges of the box, and paint it to your taste.
Leave wooden flower boxes natural for rustic charm, or paint all the sides a vibrant color so it stand out and draws attention. Stenciling shapes, alphabets or diagrams over a dull background also adds a decorative touch.
Wooden flower boxes require drainage holes---holes at the base---that allow excess water to seep out. If no drainage holes exist, irrigated or rain water collects at the base, weakening the structure, decaying wood and causing roots of contained plants to rot and die. Depending on the size of the box, drill 1/4- to 1-inch-wide drainage holes over the base before or after assembly. Larger holes allow soil to seep out. Depending on personal taste, drill these randomly apart, or space these in equally-spaced rows. Apply sealer to a small paintbrush and apply it over exposed surface of each hole to protect the wood from damage.
Waterproof the finished wooden flower box prior to planting to avoid decay or mold problems associated with moist soils. Several options to counter water-related problems exist, such as using water-resistant wood or applying exterior grade primer-sealer. Naturally occurring or processed water-resistant woods include cedar, redwood, pressure-treated yellow pine and cypress. If applying water-resistant sealer, coat each side thoroughly before assembly to ensure complete coverage. Both options are also mixed for added protection. For instance, applying water-resistant primer-sealer to lengths of wood prior to assembly ensures longer resistance.
A flower box filled with soil and plants can become quite weighty, which is why appropriate size consideration is an essential factor in construction. A narrow trough between 8 to 10 inches in height rather than a wide box provides sufficient room for planting and space for roots to spread. It also provides ease of reaching flowers in the back. Use lengths of wood at least 3/4 to 1 inch wide, and insert wood screws every 2 to 3 inches apart during assembly for added security.