Wooden planter boxes are a good solution to outdoor gardening if your space is limited or if you want to use amended soil (or organic soil) to grow vegetables or flowers and do not want to replace the soil in a whole bed. A plywood wooden planter box can be absolutely utilitarian, but there are a variety of ways to make it less plain, such as painting, stencilling, or applying tile, redwood boards, facing stone or brick.
Cut a 4-foot-by-4-foot piece (a quarter sheet) of 3/4-inch exterior grade plywood into the following pieces: one piece that is 12 inches by 18 inches, two pieces that are 12 inches by 19 1/2 inches, and two pieces that are 12 inches by 12 inches. These pieces will make a planter with outside dimensions of 19 1/2 inches long, 13 1/2 inches wide and 12 inches deep, or approximately 3 cubic feet in volume. Use a table saw or jigsaw to cut the pieces.
Cut the following pieces of 1-inch-by-1-inch pine: six pieces that are 10 inches long and two pieces that are 18 inches long. These pieces will form the cleats that will hold the planter together. Use a table saw or jigsaw.
Glue two of the 10-inch-long cleats to the short sides of the base of the planter (the 12-by-18-inch piece). Center the cleat along the side, and make the outside edge of the cleat even with the outside edge of the base. Use a good-quality exterior wood glue or marine glue. Clamp the cleats in place using C-clamps, and allow the glue to dry.
Glue the 18-inch long cleats to the long sides of the base of the planter, using the same procedure as you used in Step 3. Glue four of the 10-inch cleats to the short edges of the two long side panels (the 19 1/2-by-12-inch pieces). Use the same procedure as you used in Step 3.
Measure and mark 2 inches from the end of each cleat. Center your mark on the width of the cleat. On the 12-inch sides, put a mark exactly between the two marks you already made. On the 18-inch and 19 1/2-inch sides, evenly space three marks between the marks at the ends. Using an electric drill and a 1/8-inch drill bit, drill pilot holes about 1 inch deep at each of the marks. Using an electric driver or a screwdriver, drive 1 1/4-inch long No. 8 screws into each hole.
Measure five equally spaced marks along the bottom edge of one of the 19 1/2-inch side pieces. The marks should be 1-1/2 inches from the bottom of the side piece. Drill pilot holes at each of the marks. Apply glue along the bottom edge of one of the long side of plywood. Align the plywood so that it is even with the bottom of the base, which should be facing upward with the cleats showing. The side piece should butt up against the base and cleat and extend 3/4 inch beyond the base on each end. Drive screws into each of the pilot holes. Affix the other long side of the planter and the two short sides using the same procedure. The short sides will not extend beyond the base but will fit in between the extended long sides.
At the short edges of each of the long pieces, mark and drill three equally spaced pilot holes. Squeeze a bead of glue between the cleat and the short side of the long pieces. Drive the screws into the pilot holes. Let the glue dry thoroughly, and finish the piece inside and out with a weatherproof stain and two or three top coats of weather-resistant polyurethane.