20160423A.jpgAs you repot your houseplants into fresh soil, remember the old soil you’re removing, now too dense and too overly 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, the roots it contains 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 the equivalent of 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!

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.

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