The most important elements in making concrete planters are the right kind of cement mix, molds and a release agent. There are two ways to mold concrete planters. One involves two molds, one inside the other; the second involves sand casting. Either method works to make any size or shape planter you like. Both are simple but require patience from start to finish.
Cut the bottom half of a plastic milk jug with a craft knife so that the sides are slightly larger than the desired height of the concrete planter. Rinse and dry the inside of the milk jug.
Coat the inside of the milk jug with a release agent. Coat the four dowels with the release agent. Follow the package directions to mix the concrete topping mix.
Fill the base of the milk carton with a 2-inch layer of mixed concrete. Insert the dowels into the concrete until they touch the bottom of the milk jug. The dowels will mold the drainage holes for the concrete planter. Place them in the center, about 3 inches apart.
Coat the outside of the bowl with the release agent. Center the bowl on top of the concrete mix in the milk jug. Fill in the side space between the bowl and the milk jug with more concrete mix. Allow the concrete to dry 48 hours.
Remove the bowl. Remove the concrete planter from the milk jug. Remove the dowels. Wait at least one week before planting or decorating the concrete planter.
Make a 3-inch-thick layer of damp sand slightly larger than the desired width of the concrete planter. Make a mound of damp sand equal to the desired height of the planter. Scoop out a cavity in the mound equal to the desired shape of the concrete planter.
Cover the cavity and the surrounding sand with plastic wrap. Coat the top of the plastic wrap with a release agent.
Mix the concrete topping mix. Pour the mix into the bottom of the sand cavity to about 2 inches thick. Coat the dowels with the release agent. Insert the dowels into the concrete mix to mold the drainage holes.
Coat the outside of the bowl with release agent. Place the bowl on top of the concrete. Fill in the side between the bowl and the sand with more concrete. Allow the concrete to dry 48 hours.
Remove the bowl. Remove the concrete planter. Remove the dowels. Wait one week before using or decorating the planter.
About this Author
Katherine Kally is a freelance writer specializing in eco-friendly home improvement projects, practical craft ideas and cost effective decorating solutions. Kally's work has been featured on sites across the Web. She holds a Bachelor of Science in psychology from the University of South Carolina and is a member of the Society of Professional Journalists.