How to Cast Concrete Planters

Spread the ¾-inch plywood sheet on your worktable. You need to assemble two plywood forms, each with four sides and a base, between which you will pour the concrete. Make the inner (smaller) form 2 inches smaller in length, depth and width than the outer (larger) form, so your planter is 2 inches thick. Measure and mark the dimensions for each form on the sheet.

Cut the five sides for each form carefully with your saw. Assemble both forms. To do so, join the four sides together first with wood glue to form a square or rectangular box. Then, flip the box over and glue the base. Allow both forms to dry thoroughly for the time specified on the glue.

Lower the smaller form into the larger form. Drill a 1-inch wide drainage hole in the center of the base of the smaller form that penetrates through the base of the larger form.

Lift the smaller form and spray an even coat of cooking oil on its outside to lubricate it. Oil the inner sides of the larger form and place the plastic tubing in its drainage hole.

Prepare concrete according to label directions. Pour the specified amount of water into the concrete in a bucket and mix thoroughly.

Pour a 2-inch thick layer of prepared concrete into the base of the larger form. Shake the form gently so the top of the concrete is even.

Lower the smaller form in the bigger form so it rests over the concrete. Make sure the plastic tubing extends through the drainage hole in its base. Pour concrete between the walls of the two forms until it is 1 to 2 inches from the rim.

Leave the forms overnight to allow the concrete to cure. Once dried, pull the tubing out. Turn the planter over and pull the outer form gently so it slides off. Turn the planter back right side up and slide the inner form out. Both forms should slide out easily due to the oil. Leave the planter to dry for an additional 3 to 5 days before filling it with soil.