Garden Myths Harmful animals Mollusks

Garden Myth: An Eggshell Barrier Will Protect Against Slugs

A very popular gardening myth claims that coarsely crushed eggshells are very sharp and that slugs would tear their bodies open trying to cross them. Therefore, by surrounding a plant susceptible to slug damage with a ring of eggshells, you can protect it, because no slug would dare try to cross such a barrier.

In reality, however, the slugs secrete “slime” (mucus) precisely to protect against cuts on rough surfaces. This slime is so efficient they can even cross shards of glass without any damage. Many studies have been made about slugs and eggshell barriers and the conclusion is clear: slugs will cross an eggshell barrier as if it weren’t there and without suffering any damage whatsoever.

Until recently, though, it was simply thought that eggshell barriers were not effective. But the situation is worse than that. Eggshells, unless thoroughly cleaned to remove the inner membrane and rinsed to get rid of any remaining albumin (egg white), give off an odor that will actually attract slugs! So “eggshell barriers” are not only ineffective, they actually make things worse.

I highly recommend you visit this website: www.allaboutslugs.com/eggshell-myth-busted/. It’s an excellent source of slug info. Here are some photos from the site I’ve used to illustrate the situation. I’ve added arrows to make things clearer.

PHOTO RADAR FOR SLUGS

Set-up: 2 lettuce leaves are placed on the ground at night.

After about an hour:

A first slug arrives at the egg shell “barrier” and starts to investigate.

About 45 minutes later:

Several slugs have located the leaf surrounded by shells and are starting to chow down. They have not yet found the unprotected leaf.

The next morning

The “protected” leaf has entirely disappeared. The leaf not surrounded by shells is in better shape, but has also suffered damage.

Why Do Gardeners Still Believe This?

The information above is not new: experts have been telling gardeners for decades that eggshell barriers don’t protect plants, but gardeners seem to prefer believing in myths rather than facing reality.

Here’s my warning for gardeners everywhere: just because “everyone says it’s true” doesn’t mean it really is true! If in doubt about a gardening technique, check with a reputable authority to make sure it really is effective.

Article originally published on July 14, 2015. 

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.

7 comments on “Garden Myth: An Eggshell Barrier Will Protect Against Slugs

  1. Oh, those pictures are funny.
    The native banana slugs are not only harmless to viable plant parts, but their poop is supposedly very beneficial. They come in to eat some of the decomposing litter from the trees above, and fertilize the area in the process. They are rather . . . . creepy when they get in the way, and don’t move out of the way fast enough, but that is the worst of it. Tourists take selfies with them. A banana slug it the mascot of UC Santa Cruz!

  2. Fascinating! My new Hobby is “Myth Busting”! I wrote an article a couple of days ago titled “Charlie Chaplin Self Love Poem and The Subtle Art of Myth-Busting”. I also wrote about the “Carrot Myth” a few weeks ago Information and Disinformation – How Carrots helped win world war II. Check it out! http://www.authorjoannereed.net

    • I just loved the carrot myth. Some day I may steal your idea for my blog! Keep up the good work! There are lots of myths in the gardening world, plus in other fields, so you won’t lack for subjects.

Leave a Reply

Sign up for the Laidback Gardener blog and receive articles in your inbox every morning!

%d bloggers like this: