How to Make Concrete Planting Troughs

Locate a rectangular plastic storage container to use as the form for the trough and set it on a level surface.

Create a hole in the inside bottom of the container near one side using a drill and a 1/4-inch drill bit. Insert a wooden dowel into the hole, which creates a drainage hole in the bottom of the trough.

Locate a smaller cardboard box that fits inside the larger storage container and cut off the flaps using a utility knife. Fill the center of the cardboard box with sand to hold it steady, but do not place it into the plastic storage box yet.

Lay a plastic garbage bag over the entire storage bin and tuck it down inside snugly.

Open a bag of quick setting concrete mix and pour it into a wheel barrow. Refer to the bag's instructions and add the appropriate amount of water. Mix the concrete up using a trowel until no portion remains dry.

Fill the bottom of the storage bin with 1 to 2 inches of concrete mix and smooth it out with the trowel. This concrete forms the base of the trough.

Insert the smaller cardboard box into the center of the wet concrete and then add more concrete around the sides until you reach the top of the inner box.

Cover the entire form with a plastic bag to prevent it from drying out. Wait one week if temperatures are above 50 degrees Fahrenheit and two weeks if it is lower. Remove the plastic and grasp the the plastic bag to remove the trough from the mold.

Set the trough in a location that stays above freezing for another two weeks. Then spray it with water from a garden hose once a day for another one to two weeks to reduce the alkalinity of the concrete, which can harm many plants.