A persistent myth claims that eggshells, when crushed coarsely, are very sharp and that slugs would be lacerated when crossing them. One could therefore surround a plant susceptible to slug damage with a ring of eggshells and thus protect it, as no slug would dare to cross such a barrier.
In reality, slugs cover themselves with a sticky “slime” precisely to protect themselves from cuts. This slime (actually mucus) is so effective that they can even pass through broken glass without suffering any damage. As for eggshells, they’re a piece of cake, because they’re not sharp at all (try cutting yourself with a piece of eggshell to see for yourself).
Numerous studies have been conducted on this subject, and the conclusion is clear: slugs pass through eggshell barriers with ease and without suffering any damage. In fact, according to some studies, if the shells are not rinsed thoroughly, they attract slugs because the smell of albumin (the white part) attracts them, as does the inner membrane if it is not completely removed!
Traffic Camera for Slugs
Here is a series of revealing photos:
Setup: Two lettuce leaves are placed on the ground in the evening.
Another Gardening Myth Debunked…
Please note that this information is not new: we have known for decades that an eggshell barrier does not protect plants, but gardeners seem to prefer to rely on myths rather than reality. As in any other field, just because “everyone says so” does not make it true!
This text was first published on this blog on July 14, 2015. It has been revised and its layout has been adapted.