How to Build a Cinder Block Planter

Dig at least 8 inches deep around the perimeter of your planter area, creating a channel that is the width of the blocks. Mix the concrete in a wheelbarrow according to the directions on the bag of dry mix. Pour the concrete mixture into the channel in the dirt. Fill the channel halfway and set two pieces of rebar lengthwise around the entire perimeter. Wear safety glasses and gloves and cut the rebar with the angle grinder to fit. Fill the rest of the channel with concrete and allow it to set according to the manufacturer's instructions.

Apply a one-inch layer of concrete on top of the set foundation. Set the masonry blocks on top of the bed of concrete and allow at least half an inch between each block. Use the masonry tools to put mud in between each block. Tap each block on its outer end with the rubber mallet so that it is firmly set into the mortar between each block. Use the level and the rubber mallet to ensure that the first row of blocks is set level across the foundation.

Apply at least one inch of concrete on top of the first layer of cinderblocks, and set the next row of blocks on top of the first row. Be sure there is at least half an inch of concrete in between each block. Tap each block in place with the rubber mallet. Use the level to ensure that the second row is level against the first, and that your overall planter wall is plumb as you work your way up. Repeat this process for each cinder block layer until the planter is at the desired height.