A concrete flower pot is one of the most durable ways to keep ornamental plants on your patio or balcony. Concrete flower pots provide a sturdy base that prevents top-heavy shrubs or trees from falling over. In winter, concrete flower pots also provide insulation against cold for tender root systems. Purchase concrete containers from many garden centers, or make your own with concrete you mix yourself.
Measure and mark the wall dimensions of your concrete forms from your ¾-inch sheet of plywood. Measure and mark the floor dimensions from the ¼-inch sheet of plywood. Your outer form should have two walls 19½ inches long and 10¼ inches high, and two walls 16½ inches long and 10¼ inches high. Your inner form should have two walls 14 inches long and 8 inches high, and two walls 11 inches long by 8 inches high. The outer bottom of the form should be 19½ inches long by 16½ inches wide. The inner bottom form should be 14 inches long by 11 inches wide.
Cut out your forms with the saw. Attach the sides and bottoms of the forms to one another, using wood screws.
Cover the inside of the outer form and the outside of the inner form with paste wax. This will help you pull the forms away from the concrete container once the concrete hardens. Place the 2-inch sections of PVC pipe end down into the bottom of the exterior form. The pipe pieces should be aligned at the center width of the form, and spaced evenly along its width.
Pull on rubber gloves and wear them throughout the concrete mixing process. Prolonged contact with concrete will burn your skin.
Fill a bucket with one part cement, two parts sand and three parts pea gravel. Add water and stir with a trowel until the mixture is the consistency of cake batter.
Pour cement into the bottom of the form to a depth of 2 inches. Make sure that the cement does not move the pipes or run under them. Smooth out the cement so that it is level with the top of the pipes.
Place the inner form on top of the cement and center it so that the gaps on all sides are the same width. Pour concrete into the sides. Press the inner form down so that the concrete does not run underneath it. Tamp down the sides with your trowel to dislodge any air bubbles. Pour until the concrete reaches the top of the mold. Smooth the concrete around the top and keep damp with a spray bottle. Wait 24 hours for the concrete to set.
Remove the inner form. Dampen the concrete with the spray bottle and wrap the project in plastic sheeting to help hold the moisture in. Check the concrete every day to ensure that it is still damp. Spray the concrete with water as needed to dampen it again.
Release the outer form from the flower pot after seven days.