Make Concrete Planters

Making your own concrete planter is a surprisingly easy and inexpensive way to create the indoor or outdoor plant housing that your specific garden needs. You can create your own mold from cardboard, or use dishes, pre-made molds, milk cartons, practically anything you want. The type and number of plants you plan on housing should determine the size and shape of your planter.

Steps

  1. 1-Choose your molds. You will need an outer mold and an inner mold of same shape but different size.
  2. -The smaller mold should nestle inside the larger with a gap of about 2 inches or 5 cm. The gap between molds will be the thickness of your planter's walls. If your planter will be any larger than {{safesubst:#invoke:convert|convert}} by {{safesubst:#invoke:convert|convert}}, the walls should be 3 inches or 7.5 cm thick.
  3. - You can create your own mold by cutting two cardboard boxes, the inner and outer mold of your planter, to the size you want.
  4. - Glass, plastic, cardboard and stainless steel are all common choices. Styrofoam also works well.
  5. - Spray the inside of your molds with mineral oil or spray lubricant. This will help you remove it later. If you use a glass mold, if you coat the glass in lubricant you may not have to break the glass when you remove the molds from the planter.
  6. -Mix concrete in a tub or wheelbarrow. Crack-resistant concrete is your best bet. Pour the desired amount of concrete into the tub or wheelbarrow, then add water and mix gradually, until you have consistency similar to cake batter. Follow the instructions on the packaging.
  7. - Protect your hands with kitchen gloves while handling concrete.
  8. -Feel free to add decorative glass, pebbles, shells, beads or other materials as you see fit, so long as you do not drastically alter the concrete mixes consistency.
  9. - Pour concrete mix evenly into the bottom of the outer form mold, creating a base.
  10. -If you want to add drainage you can embed drainage pebbles in the base now, or drill holes later (at least two days after the concrete has dried).
  11. - Even and smooth out the concrete mix with a trowel.
  12. - Press the inner form mold down onto the concrete mix until the base is at your desired thickness. The base and the walls should be of similar thickness, though the base can be thicker than the walls (usually not the other way around).
  13. - Pour concrete mix into the space between your molds. Tamp continually with a trowel and push the concrete mix along the edges of the mold to ensure smooth walls and avoid air bubbles.
  14. -When you reach the top of your planter, even off and smooth with your trowel.
  15. - Lightly bounce your planter now, to help the concrete consistency (be careful not to break glass molds).
  16. -Wrap the planter in plastic, and let it sit for about 36 hours.
  17. - Test the strength of the concrete with a screwdriver or knife. If you can make an impression, the concrete is still too wet.
  18. - Slowly remove the inner form mold. If you used cardboard, you should be able to peel it off. If you used glass you might have to break it, though mineral coating or lubricant might allow you to salvage glass molds.
  19. - Remove the planter from the outer form mold.
  20. - Smooth out the planter's surface with a rough brush or scouring pad.
  21. - Allow the planter to sit for another week.
  22. - Rub your planter with a wet sponge or cloth until its color darkens, once a day.
  23. - After drying for at least two days, you can drill drainage holes in the base.
  24. Set the planter in the sun, pour your soil, and add your plants!

Tips

  • If you are using cardboard molds, you might consider buttressing the outer mold with blocks of wood while the concrete is drying so that it doesn't lose its shape.
  • If you are using wood molds, apply caulk to the seams, and line the mold with plastic so that concrete does not seep into the seams.
  • Placing a light weight, such as a paperback book, on the bottom of the inner mold after Step 6 will help keep the concrete mix from rising.
  • Do not pour concrete when rain is expected, or when temperatures are below 50 degrees fahrenheit or 10 degrees celsius.

Warnings

  • Protect your hands with kitchen gloves while working with concrete.
  • Do not house plants in your homemade planter until several days after finishing your mold.

Things You'll Need

  • Crack-resistant concrete mix
  • Rubber gloves
  • Two molds of the same shape but different size
  • Mineral oil, non-stick cooking oil or spray lubricant
  • Tub or wheelbarrow
  • Trowel
  • Plastic sheeting or trash bag
  • Drill (optional, if you are adding drainage holes)
  • Drainage pebbles (optional)
  • Decorative mix additives such as pebbles, stones, glass or shells (optional)

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Sources and Citations

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