How to Make Concrete Flower Planters

Select two sturdy cardboard boxes to use as molds. The center box needs to fit evenly within the larger box to create a planter with 2-inch walls. If you decide to make a planter bigger than 2 feet by 2 feet, the walls need to be 3 inches thick.

Set up close to a water source in a shady area of your yard, where your finished planter can cure for three weeks. Spray the boxes with the mineral oil or spray lubricant to aid in their removal later on.

Pour dry concrete mix into your wheelbarrow. Add water gradually and mix until just moistened to the consistency of thick mud. Squeeze the mixture in your hands to test that it is neither dripping wet nor crumbling apart.

Using a shovel, fill the bottom of your larger box with 2 inches of concrete and pack it down. Center your smaller box inside the larger box to create the mold for the sides.

Using the shovel and trowel, gradually scoop concrete mixture into all four sides and use a tamper to compact the concrete as you go. Smooth and level the top edge when full.

Cover with plastic and cure in the mold for 36 hours. Carefully pull away the cardboard boxes to release the concrete planter. Smooth out any rough edges with your stiff wire brush.

Add texture or design to the outside planter walls by carving with a screwdriver or other sharp tool, if desired. Handle the planter carefully at this stage because the concrete has not fully hardened. Leave planter outside in the shade for three weeks to finish curing.

Embellish dry concrete planters by gluing marbles, broken pottery, tile, pebbles or trinkets onto the cured concrete planter using epoxy, liquid nails or grout. Decorate your cured concrete planters with latex or oil-based paint if desired.