Failed Project: Keeping Snails Away From a Vegetable Garden

When growing own vegetables one of the challenges faced is to keep predators away from the fruits and leafage. A feared creature in this context is the snail. This Instructable documents a fruitless attempt to refuse these animals access to the vegetable garden by using a dedicated but harmless fence. Step 1 documents the design criteria and Step 2 describes the test setup. Step 3 shows why the fence is not effective in stopping snails and slugs.

An alternative but likewise not very effective attempt has been documented in Step 4 of this Instructable: attracting snails to places from where they can easily be caught and then evicted from the vegetable garden. Experiments using Upside Down Dinner Plates on the soil (snails are attracted to the early morning condensate, preventing dehydration) showed a hit-rate of approximately 10%. Note that the setup described in Step 4 might not work at all under some climatic conditions.

Step 5 documents some other suggestions for dealing with the animals in a way that is ecologically sound and, most probably, much more effective than the efforts presented in Steps 1 to 4.

The purpose of documenting these attempts in an Instructable is to share the lessons learned and to possibly benefit from the experience from others that have dealt with the same problem. As the pictures have been licensed under CC BY they can be reused in other Instructables (thereby mentioning openproducts).

Another gardening-related Instructable by Openproducts is the Multi-Row Hanger for Gardening Tools.

The following design criteria have been applied for the fence:

 - Animal friendly functioning: just block the way through, no pain or death involved;
 - Environment friendly: use non-toxic materials, no poisonous substances, no impact on growing process for the vegetables;
 - No maintenance required: the purpose is to realize a lower snail-density inside the vegetable garden and a higher snail-density outside the vegetable garden, without the need of evacuating the snails (this criterion is not met in the solution described in Step 4 of this instructable, the Upside Down Dinner Plates);

The targeted basic principle is to create a barrier that is simply uncomfortable for the animal: the idea is that the snail prefers to crawl along the fence instead of crossing it. The second criterion resulted in the choice of untreated wood as a construction material.

The next step describes the test setup and Step 3 documents the effect of the fence.

For the purpose of testing it was considered sufficient to create a small triangular area (approximately 50 square cm) bordered with a fence of a few centimeters high. The fence has been made by lining up cocktail picks and might look quite scary from the ground because of the life-sized sharp tips. Would the test have been successful, the plan was to micro-fence the whole border of the vegetable garden. 

A snail and a slug were placed inside the walled area, surrounded by delicacies (spinach leaves) to provide an incentive for breaking out.

It was impressive to see that the sharp edged fence had no perceptible effect on the snail in question, it just elegantly sneaked away over the tips. The snail was examined after the event and was found in perfect shape.

The same applies to the slug, with the only difference that it decided to benefit from a weakness in the test setup design, namely the edges. This is really smart.

As a reward of demonstrating their capabilities for breaking out the test setup the delicacies were all granted to the animals.

Thus it has sufficiently been demonstrated that a fence as used in this instructable is not effective, and the project can be considered a failure.

The next step shows an alternative approach using Upside Down Dinner Plates.

An alternative but likewise not very effective attempt is to attract snails and slugs to places from where they can easily be caught and then evicted from the vegetable garden. Experiments using Upside Down Dinner Plates on the soil (snails and slugs are attracted to the early morning condensate) showed a hit-rate of approximately 10% (in one month a number of approximately 50 snails and slugs have been caught using fourteen plates). Note that this setup might not work at all under some climatic conditions. It is important to leave an opening for the snails and slugs to enter their hiding-place.

Main drawback to this approach is that it's a lot of work to turn over all dinner plates every morning, especially since a minimum number of plates seems to be required for assuring sufficient coverage. Moreover it's not a very pleasant job to collect the animals and evacuate them to places where they do less harm.

It would be a nice follow-up project to design an Arduino-based detection system: a flashing LED indicates when a snail is detected under the dinner plate, to ease the efforts of the detection process. Another improvement regarding aesthetics: use brown plates instead of white plates.

The next step documents some other suggestions for dealing with snails and slugs in a vegetable garden. These suggestions are not so much to fight the molluscs but rather to understand them and to make them behave in a way that is easier to control, all in an ecologically sound way.

First of all it is important to stress that snails and slugs in principle are beneficial to a garden. As most of the species prefer rotting plants over fresh leaves the animals are not always a threat to a vegetable garden. Moreover, snails play a role in the lime balance of a land. Natural enemies of snails and slugs are the hedgehog and some birds. Their eggs are being eaten by many birds, insects and rodents. Birds are attracted by a garden with a lot of slugs and snails.

Some plants appear to have the effect of chasing snails and slugs. Planting these in the vegetable garden in combination with the creating of a natural habitat for snails, slugs and their predators nearby might be the road to success. This means that fallen leaves and branches should be left on the ground, or at least collected and stored inside the garden.

Based on the above, including the failed projects in the previous steps, it can be concluded that a more natural approach to snails and slugs management is likely to be more effective than fighting them. Note however that it might take quite a while before a satisfactory equilibrium has been restored.  The approach with the 'Upside Down Dinner Plates' as documented in Step 4 may speed up this process, although it might feel like carrying coals to Newcastle.

This Instructable is made available through a Creative Commons Attribution (CC-BY) license.

Republishing this Instructable is allowed, provided it is being attributed properly (cite the name Openproducts, link to www.openproducts.org or www.instructables.com/member/openproducts or the original Instructable. For other arrangements send a Private Message through the instructables member page (www.instructables.com/member/openproducts).

Although this Instructable can be considered a failed project it may still be a good starting point for an exchange of ideas and experiences. The 'Natural Snail and Slug Management' suggestions in Step 5 offer relevant information. Feel free to post your suggestions as a comment to this instructable.

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