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How to Reuse Potting Soil From Last Year

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How to Reuse Potting Soil From Last Year

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Overview

Potting soil serves as the home for container-bound plants. It provides nutrients, holds water and protects plant roots from excessive temperature changes. The prevailing thinking is that gardeners should replace all container soils every year. Full replacement of container soils creates a big expense. Budget-conscious gardeners do have options to conserve soil and save money. It requires a lot of effort and time to properly recycle potting soil. Weigh the effort against the benefit to determine if it's right choice for your container garden.

Step 1

Remove all foliage and roots from the potting mix. Sift through the mix to check for buried pieces of roots. Discard any potting soil that contained diseased, dying or infected plants during the previous growing season.

Step 2

Pour loose potting soil into one plastic tub. Continue adding sifted soil until all potential planters have been emptied into this larger container. Consider this soil "dirty" and do not mix new or purified potting soil in this container in the future.

Step 3

Set the oven temperature to 200 degrees F. Pour a layer of potting soil into a large aluminum pan and spread evenly across the surface, as recommended by Colorado State University Cooperative Extension. Don't mound the soil in the middle of the pan or extend the soil above the edge of the pan.

Step 4

Place the potting soil mixture into the oven for 2 hours on the lowest rack. Carefully remove the pan from the oven with potholders after the allotted time and allow it to cool for an hour. Dump the entire contents into the wheelbarrow or onto a tarp, advises The Oregonian newspaper online. Continue cooking and dumping all the potting soil to permit easy addition of amendments to a large volume of sterile potting soil.

Step 5

Add peat moss or perlite, in total quantity equal to about a quarter of the volume of sterilized soil and mix completely, advises The Oregonian. Peat moss boosts the soil's organic content and perlite improves moisture retention.

Step 6

Perform a soil test on the reworked potting soil. The pH level will probably be lower than the preferred level of 6.8. Add lime to the mixture based on recommendations on the product packaging.

Step 7

Add 1/2 to 1 cup of granulated fertilizer or commercial compost to the mixture and distribute evenly. Transfer the entire mixture to a clean storage tub for use in future container gardens. Store in a covered container or in a sheltered location.

Tips and Warnings

  • Most garden specialists recommend never reusing potting soil. The practice raises the concern of potential exposure of new plants to soil borne diseases. Clean and reuse potting soil at your own risk.

Things You'll Need

  • Two large plastic tubs
  • Hand trowel
  • Large aluminum baking pans
  • Peat moss
  • Perlite
  • Granulated fertilizer or compost
  • Soil test kit
  • Powdered lime
  • Wheelbarrow or tarp

References

  • Colorado State University Cooperative Extension: Seed Start and Transplants in Sterilized Soil
  • Oregon Live: Rejuvenate Potting Soil
Keywords: cleaning potting soil, reusing potting soil, sterilizing potting soil

About this Author

S.F. Heron is an avid gardener with three years of experience in online writing and a working background in aviation and earth and ocean sciences. She is published on various sites, including Helium, eHow and Xomba. She holds a Bachelor of Science degree in journalism from the University of Maryland.