How to Build a Concrete Block Planter

Garden planters add special definition to your garden. The walls can form boundaries from one part of your yard to another. Building these planters from scratch rather than buying them from a store gives you a lot of flexibility. You determine the size and shape of the planter as well as its depth. Built-in planters also add permanence to the yard, called hardscape. Hardscape helps make an outdoor space feel finished.

Tape measure

Spray paint

Shovel

Concrete

Cement blocks

Mortar

Rebar

Trowel

Dig a trench around the perimeter of your planter. Dig 8 inches deep with straight sides. Mix concrete and water in a large wheelbarrow according to package directions. Pour the trench half full of concrete. Lay two pieces of 1/2-inch rebar in the trench on all sides. Fill the trench with concrete. Let the foundation set overnight.

Spread 1/2 inch of mortar on the bottom and sides of an L-shaped block. Set the block in the corner of the planter. Lay the entire first row, or course, of blocks.

Set the second row of blocks. Set each block so its joint is centered over a block beneath it.

Slide rebar into the space inside the block. Set 15-inch rebar into the open space of every other block. Pour concrete into the hole with the rebar to fill the space.

Set any additional rows of block you may want, depending on your planter’s size and height.

Spread mortar along the bottom and sides of a concrete cap piece. Set the cap on top of the wall. Leave two inches of overhang on the sides of the planter. Let the mortar set overnight.

Paint your concrete block to coordinate with your home’s color scheme. Use outdoor masonry paint on the concrete block.