Reusing Potting Soil

Overview

Instead of discarding old potting soil when you're transplanting your plants or repotting your container garden, reuse it to save yourself money. Although old potting soil is often devoid of minerals and nutrients and sometimes infested with diseases and insect pests, you can sterilize your potting soil and restore its nutrients to make it ready and safe for re-filling your containers.

Step 1

Preheat your oven to 180 degrees Fahrenheit. At that temperature, according to the Washington State University, most plant disease-causing bacteria and viruses will be killed, as well as weed seeds and insect pests. You can "bake" old potting soil in the oven to sterilize it.

Step 2

Pour the potting soil you wish to reuse into a metal or glass baking pan. Layer the soil no deeper than 4 inches. If you have more potting soil than that, you'll need to do this step in multiple batches.

Step 3

Place the pan in your oven and let the potting soil bake for 30 minutes. Remove the pan after the time is up and allow the soil to cool to room temperature.

Step 4

Pour the sterilized potting soil into a bucket and add perlite and compost. Measure the compost and perlite so they each equate to approximately 30 percent of your sterilized potting soil's volume.

Step 5

Use the sterilized, amended potting soil just like you would any other potting mix.

Tips and Warnings

  • Don't let your potting soil heat up to 212 degrees Fahrenheit. At that temperature, various toxins may be released by the heat, according to Washington State University.

Things You'll Need

  • Old potting soil
  • Baking pan
  • Oven
  • Compost
  • Perlite

References

  • "The Complete Houseplant Survival Manual"; Barbara Pleasant; 2005
  • Washington State University: Soil Treatment Procedures
Keywords: reuse potting soil, sterilize potting soil, use old soil

About this Author

Josh Duvauchelle is an editor and journalist with more than 10 years' experience. His work has appeared in various magazines, including "Honolulu Magazine," which has more paid subscribers than any other magazine in Hawaii. He graduated with honors from Trinity Western University, holding a Bachelor of Arts in professional communications, and earned a certificate in applied leadership and public affairs from the Laurentian Leadership Centre.