Laidback Gardener Tip of the Day

Yes, You Can Compost Diseased Leaves

This is a repeat… but I’ve had 2 questions on the subject over the last week, so obviously there’s a need to release the information a second time.

octobre 5

One hears the strangest things out of the mouth of “experts” sometimes. One of the stupidest is that you must never recycle diseased leaves, such as those with tar spot, powdery mildew or apple scab, for use in compost or in mulch. They insist you must either burn infested leaves or bag them and put them out on the street so the municipality can pick them up and destroy them.

Now this seems to make sense. By destroying leaves bearing the spores of a disease rather than recycling them as mulch or compost, which doesn’t always do the job, won’t you help control the disease? Actually, there is no proof that this makes one iota of difference.

For leaf diseases already present throughout a region, the horse is already out of the barn, so to speak. The disease is out there and unless you destroy every single infested leaf (which is nigh to impossible), you will never be able to control it. It only takes one spore-bearing leaf to infect a hundred plants… and no cleanup campaign will ever get every single leaf throughout a region. Having big trucks haul the leaves away for burning is simply polluting the air for nothing. When I hear the same town recommend, as mine does, recycling leaves on the one hand and not including diseased leaves in compost or mulch on the other, I always imagine the poor gardener, sitting on the ground sorting through thousands of leaves one by one!

This reminds me of the old belief that you had to burn the leaves and stems of mildewed phlox and bee balm (Monarda) each fall to prevent the disease from returning. I did this faithfully year after year and the disease came back every time. I even set one phlox plant ablaze one fall to see if that would work. The plant came back the next spring, but was as diseased as all the others by fall. I eventually found a technique that did work: I removed the disease-susceptible plants and replaced them with disease-resistant varieties. Problem solved!

Let’s get real! WIth wide-spread leaf diseases, the damage is already done. So why not use the affected leaves ecologically by recycling them as compost or mulch? Mother Nature has been doing this for millions of years: don’t you think she knows best?

Larry Hodgson is one of Canada’s best-known garden communicators. After studies at the University of Toronto and Laval University where he obtained his B.A. in modern languages in 1978, he succeeded in combining his language skills with his passion for gardening in a novel career as a garden writer and lecturer. 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 is a regular contributor to and horticultural consultant for Fleurs, Plantes, Jardins garden magazine and has written for many other garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening, Rebecca’s Garden 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 50 other titles in English and French. He can be seen in Quebec on French-language television and was notably a regular collaborator for 7 years on the TV shows Fleurs et Jardins and Salut Bonjour Weekend. He is the President of the Garden Writers Association Foundation and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. An avid proponent of garden tourism, he has lead garden tours throughout Canada and to the gardens of over 30 countries over the last 30 years. He presently resides in Quebec City, Quebec.

2 comments on “Yes, You Can Compost Diseased Leaves

  1. For the first time in years, my maple currently has no sign of tar spot (which it usually has by now)– anyone else? I attribute it to the heavy rains here in early summer dampening spore travel. Thoughts, Larry?

    • It could certainly be that. Really dry weather in the spring (no chance of that this year) can do it as well. Unfortunately, the disease isn’t gone: the spores are still out there, waiting for the right conditions to attack!

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