Repotting Soil

Recycle Your Used Potting Soil!

Hands removing old potting mix from a houseplant.

Don’t throw out your used potting soil: reuse it! Photo: pistilsnursery.com

By Larry Hodgson

As you repot your houseplants into fresh soil, remember the old soil you’re removing, now too dense and excessively rich in mineral soils for reuse directly as a potting mix, can still have a second life.

The most obvious thing to do is simply to add it to your compost bin. Since it is extra-rich in minerals (mineral salts tend to build up in houseplant soil over time), it will stimulate the microbes present in the compost to work even more diligently, resulting in faster composting. In addition, any roots it contains will decompose quickly, adding yet more humus to the compost you’re creating.

Don’t worry about the presence of perlite and vermiculite in the mix. They are simply expanded rocks and no more harmful to the environment than particles of sand would be. They’ll help structure the compost when you use it in the garden later.

Another possibility is to mix old houseplant soil into the ground as you plant or transplant perennials, shrubs, vegetables, etc. Consider it to be similar in its results to adding compost to the soil.

Or simply spread the old mix over the soil among established plants (perennials, shrubs, etc.), again just as you would do with compost. They’ll then be able to profit from the minerals the used potting mix will release.

In fact, about the only thing you shouldn’t do with old potting soil is to throw it in the trash: that would be a waste!

Adapted from one originally published on this blog on April 23, 2016.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

11 comments on “Recycle Your Used Potting Soil!

  1. I agree. Nothing wasted here. Plus, it does benefit our plants. Been doing this for years with no problems. Besides, if you throw this away, it’s like throwing dollar bills in your trash. Thx guys for your posting. Happy gardening.

  2. Pingback: Recycle Your Used Potting Soil! — Laidback Gardener – Ninnys Nest

  3. Your article on recycling used potting soil is good common sense and one that I hope many gardeners will employ. I’ve worked at a nursery for over 30 years and have bought many annuals, perennials and houseplants over the years and always use the old potting mix.. I used it to top dress and reseed if I have bare spots in the lawn. I also top dress around my perennials and flowering shrubs. The professional potting soil the growers use also contains a slow release fertilizer that is still viable and gives the plants a great boost..

    New Jersey

  4. Margaret

    I cold compost; don’t have the upper body strength to do all that turning and aerating. Adding used potting soil to the mix speeds up the process and yields a really nice humus-y product. And how would you get rid of used potting soil anyway,

  5. All the ‘crud’ generated in my garden gets used for canning tough perennials like agapanthus. They are not at all discriminating, and will be in a garden somewhere before they realize that they were cheated.

  6. Rosemary

    I kept the potting soil used in containers from last season. I’ve often wondered if it would it be ok to re-use it this year’s containers?

  7. rosemary

    Thanks!!!

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