Some people believe that crushed eggshells can be used to form snail and slug barriers.
Is this just another garden myth, or is there something to it?
In theory, crushed eggshells are so sharp that slugs and snails would hurt themselves climbing over them.
Shells scattered around the plants would therefore build defensive walls.
Critical voices argue that snails and slugs – e.g. the Spanish slug – would easily crawl over razor blades.
Why should eggshells be a problem for them?
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How Might Eggshells Be Used Against Slugs and Snails?
In practice, eggshells are dried and then crumbled into very tiny, sharp-edged pieces, for example, with a rolling pin.
Some people claim that it is crucial to use only the shells from uncooked eggs.
Cooking the eggs would reduce the sharpness of the shells.
Others say that their effectiveness depends on the moon cycle.
They recommend that crushing the shells works best with a decreasing moon and that you should spread them with a waxing moon.
The following video explains the theory.
Video: The eggshell theory
Crushed Eggshells: Field Test
Since there is still much discussion on this topic, I carried out a simple test.
I dried and crushed the shells of uncooked eggs.
Then I placed them on a table and formed a little wall of around two inches (five centimeters) wide and put some snails and slugs in the middle.
What happened next is shown in the following time-lapse video.
Video: The eggshell test
Unfortunately, the experiment showed that eggshells do not really work in the battle against slugs.
The slugs were not afraid of the shells and crawled over them with little hesitation.
One snail, however, was unwilling to cross the eggshell wall.
You can see clearly that it was put off by the shells.
The same was true for the leopard slug at the beginning of the video.
But after a few attempts, it finally made its way over the barrier a few times.
The final evaluation of this method of controlling slugs is not clear.
The slight repelling effect could have been the result of the wrong application.
Perhaps the shells were not small enough.
Or they went over them because they were left only with a small way out, so they had to take the route over the shells to escape.
It may also have been due to the influence of the moon that the results turned out to be poor. (I did not stick to the recommendations regarding the moon cycle.)
Personally, I doubt the influence of the moon could make a big difference in this matter.
In the end, I am skeptical that eggshells are an effective slug control method.
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If you would like to try this method but you do not have enough eggshells you could buy some.
There is eggshell powder on the market, which is sold as a dietary supplement for dogs. This could be used.
One good thing about this method is that if you eat eggs, you will get the shells for free.
In addition, the soil profits from the application of the shells.
The minerals they contain contribute to the improvement of soil health.
Alternatives to Eggshells
There are other mulch materials that are supposed to work as snail and slug protection.
For example, sheep wool pellets work as a slug repellent, a fertilizer, and a mulch at the same time.
A comparison of different materials, further tests, and information can be found here: mulching material against snails.
Slug Control Alternatives
Some other slug control methods might interest you:
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Last update: July 11, 2019
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