AS ANYONE WHO HAS EVER STROLLED through the nursery knows, outdoor pots can add up. Try this straightforward method for making a concrete outdoor planter to spruce up your stoop.
1. Make a mold
A concrete mold or formwork is used to hold the concrete in place while the material hardens to the desired shape. For this project, the mold will have two parts: the exterior vessel, which will dictate the planter’s overall shape, and an interior vessel, which will fit inside the first to create the cavity needed for the plant’s root ball and dirt. The mold doesn’t have to be complicated. You can reuse objects, like cardboard boxes, or two different-sized plastic buckets.
2. Add Drainage
If you want a drainage hole at the bottom of the planter, glue or tape a 1- to 2-inch piece of plastic tubing to the inside center of the exterior vessel. The interior vessel will sit on top of this tube during construction.
3. Mix the concrete
Bags of unmixed concrete can be found at any home improvement or hardware store. In a separate container (not one being used for the mold), mix the concrete powder with water according to package instructions. You might need more than one bag, depending on your planter size. The concrete’s desired consistency should resemble porridge or peanut butter.
4. Spray and pack
Using cooking oil or WD-40, spray the walls of the mold that will touch the concrete. Pack concrete inside the bottom of the exterior vessel, around the drainage tube. When the concrete is level with the top of the tube, place the interior vessel inside, then put weights inside it for added stabilization. Continue to scoop concrete into the gap between the two vessels, tapping the exterior with a mallet to settle the cement and remove air bubbles.
5. Let it cure
Cover with plastic and allow the concrete to dry for at least twenty-four hours. Remove the molds by gently tapping the exterior with a mallet or cutting them away with a utility knife. Leave the planter to finish curing for several more days before planting.