Dealing With Slugs & Snails Without Harming Your Garden

Is there a way to stop slugs and snails from destroying plants without harming other animals or the environment? Let’s look at the pros and cons of beer traps, slug bait, copper wire, sharp eggshells, and more.

Also see 45 Ridiculously Simple & Helpful Eco-Beneficial Garden Tips for more ideas for your growing space.

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Slugs & Snails In The Garden

It is never fun to inspect your garden plants only to find that slugs or snails have eaten your newly-sprouted seedlings or created gaping holes on tender leaves. Hostas, lettuces, delphiniums, dahlias, cabbage, strawberries, and peppers are just a few of their favorites.

Depending on how rainy your climate is, they may come in numbers great or small. The higher the moisture levels, the higher the slug and snail populations.

But, as with any “pest” problem, the first step is to clearly determine that it really is a problem—and one that warrants action.

Then, research which options you have to safely protect your plants—or at least some of them— without causing harm to the ecosystem. Many popular slug “solutions” are neither good for the garden or wildlife.

Because these odd, slimy creatures are food for so many animals including birds, frogs and toads, hedgehogs, beetles, spiders, snakes, lizards, and more, eliminating them is not an option.

To deal with them, we have to manage our expectations—accepting their role in nature—and come up with tactics that save some of those juicy lettuce leaves for us.

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Contents

• Slugs & Snails – What are they?
• Identify The Problem
• Easy Ways To Deal With Slugs
• Slug Bait Products
• Alternative DIY Slug Deterrents
• Summary
• Resources

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Slugs & Snails

There are thousands of species. Many live in water. Some live on land. They are well-adapted to a variety of conditions across our planet.

The ones that bother gardeners are a small subset of land dwellers that eat plants.

No matter what type, slugs and snails are ecologically important, playing a vital role in recycling dead plant material and animal waste while also acting as a food source for a range of animals.

This is why use of the term “pest” is discouraged—they definitely have their place in nature.

Identify The Problem

How can you tell if slugs are eating your plants?

Slugs can be difficult to catch in the act. They usually feast by night (or on rainy, overcast days) when conditions are dark and moist. By day, they hide away, preventing the hot rays of the sun from drying them out. They must remain hydrated to survive.

Sometimes your only evidence—besides the damaged seedlings or plant leaves—is a slime trail (from the mucus covering their bodies) on rocks, pavers, or wood, leading to or from the crime scene.

With potentially hundreds or thousands of species (depending on your location), you can’t even assume whatever slug or snail you find in your garden is the culprit. Many have no interest in your plants at all—they are busy doing other things.

Plus, countless other animals including caterpillars also eat plant foliage—it’s how they survive—so we begin with a lot of names on the suspect list.

This is why some of us resort to some night-time investigating—particularly after rain or watering to confirm whether or not slugs are indeed the problem.

With flashlight in hand, inspecting vulnerable plants in the dark may catch the diners mid-munch.

If you find them, take mugshots, identify the species (I use Google Lens), and learn safe ways to reduce future damage.

If you like doing this, consider getting yourself a headlamp and make hand-picking slugs your new night time gig.

Are there any plants slugs and snails do not like? Apparently they will avoid foxgloves (Digitalis) and go for other options.

Easy Ways To Deal With Slugs

Let’s look at some easy methods used to control snail and slug populations. By “easy” we mean, simple to implement: we’re not here to eradicate them or cause other harm to the eco-system.

Encourage Natural Predators

Recommended

Creating a biodiverse habitat is not a fast solution but it is the ongoing, long-term goal for those of us wanting to create healthy garden eco-systems.

When there is too much of something like slugs, a natural solution is to attract more predators, allowing nature to return the balance.

This means growing—without any pesticides or herbicides—a diverse selection of plants suited to your climate, region, and conditions that support local wildlife who enjoy eating slugs.

Pets like ducks, geese, and chickens are also big-time slug fans. Hand-pick what you find and give them to your pets as treats.

Ponds are also a fantastic way to attract all sorts of slug-eaters that would otherwise have no interest in your yard. Frogs and toads are two good examples.

This has advice for starting a new garden pond and these tips show how to keep frogs happy once you’ve attracted them.

Nematodes

Not Approved In North America

In the United Kingdom and across Europe, there is one specific species of nematode you can buy that will kill slugs and snails. Product names include Nemaslug and NemaKnights (Amazon UK). These work on a biological level, infecting the slug and overtaking its behavior, essentially transforming it into a zombie.

Because this nematode is not native to North America, it has not been approved for use here. This may change at some point as it has been found in parts of the United States in recent years.

The Problem With Buying Beneficial Nematodes For Grub Control explains some pros and cons of using nematodes in the garden.

Add Physical Barriers

Recommended

The most immediate, preventative solution for stopping future slug damage is to create physical barriers that make it impossible for the slugs to reach your seedlings or plants.

The idea is to surround the plant stem with something the slug cannot climb over or through.

• Use plant collars or bottomless flower pots to completely surround the plant stem, (hopefully) prohibiting the slug from climbing up and over. Realistically, this could become a lifelong experiment!
• For young plants and seedlings, I like (upside-down) wire mesh waste baskets placed right over the plants, pinned to the ground with tent pegs. These will keep all sorts of animals out including slugs. This shows numerous additional garden uses for these waste baskets. Look for them at dollar stores where they should be just a buck or two.
• Placing plant containers up off the ground can also help. It’s a lot of work for a snail to climb up on a patio table and into a container of salad greens when there are more accessible foods at ground level. This has helpful tips for growing vegetables in pots.
• I use mesh or hardware cloth screens over my raised beds for any crops that do not require pollination. These keep out a range of animals including squirrels and birds and would certainly block slugs as well.
• Eggshells (more on this here) are also commonly recommended as a barrier but they do not work.

This said, the use of physical barriers is not realistic in large gardens with huge slug populations. If you have a sea of hostas in open beds, you’re growing an all-you-can-eat slug buffet.

Long-term, if the problem is really bad, it may come down to some combination of changing plant choices, using containers, setting up some physical barriers, ongoing hand-picking, and use of wood lumber or beer traps.

Remove Or Add Hiding Spots

Recommended

During days when it’s hot and sunny outside, slugs will retreat to any cool, moist spots they can find, otherwise they risk drying out and dying (“desiccating”).

If they are doing damage by night, they are hiding nearby by day.

Remove Hiding Spots

Determine and remove any hiding spots near the plants you most want to protect.

Popular slug hangouts include the underside of flower pots, under layers of mulch, and at the base of long grasses.

You can also find them on the underside of boards or bricks around the perimeter of a raised bed.

Create Temporary Hiding Spots

To attract and collect them, try putting a piece of wood lumber or damp cardboard on the ground near their favorite dining spots and leave it overnight. The next day you should find plenty of them congregating on the underside.

Slug Bait Products

There are two main types of slug baits, also called molluscicides.

Personally, I would not use any of these.

Baits With Metaldehyde

The most popular slug baits have been around since the late 1930s. These are products with metaldehyde which cause slugs to over-produce mucus and dehydrate. Unless the affected slug or snail gets some water quickly, it will die.

In March 2022, a UK ban on metaldehyde came into effect due to concerns about its effects on wildlife and the environment, especially water systems.

You definitely have to keep pets away from it. It can cause tremors, seizures, and high body temperatures. A study in the Journal of the American Veterinary Medical Association found 35 reports of dogs dying from exposure to metaldehyde reported to the U.S. National Pesticide Information Center from 2001 to 2011.

Despite all this, it is permitted just about everywhere outside the UK.

Baits With Ferric Phosphate

Following the metaldehyde ban, the UK government touted baits with ferric phosphate (iron phosphate) as an effective and safer alternative. This type of bait stops slugs from eating and they eventually die.

Sluggo is one well-known brand.

While it does seem to be an improvement over metaldehyde, iron phosphate pellets can be toxic to earthworms.

It’s not the iron phosphate alone that is the issue but the added chelating agents. These agents make the metals more soluble for easier uptake by the slug.

Because there is no requirement for manufacturers to disclose those substances on the label—and many of them are not quick to volunteer this information—you often don’t know what you’re getting.

A 2012 report for the U.S. Department of Agriculture said that all iron phosphate slug baits marketed in the U.S. appeared to include chelates.

Alternative DIY Slug Deterrents

There are countless DIY-type recommendations for slug control. All of them have their supporters who say they work. But, without proper control studies, we just can’t know (a.k.a. anecdotal evidence).

In 2018, in response to the upcoming metaldehyde slug bait ban, The Royal Horticultural Society (RHS) in the UK spent several months testing alternative slug controls. Tests included eggshells, copper tape, grit, pine bark mulch, and wool pellets.

The conclusion?

None of them worked.

To be fair, these tests took place in just in one location with one kind of plant and one set of slug species—conditions that will vary greatly for each of us.

The results were not definitive but, in that setting, nothing tested was a “discernible deterrent” to slugs. There was the same amount of damage on plants with or without any of these purported deterrents.

Here are some common “solutions” and what we know about them.

Salt

Not Recommended

Salt (sodium chloride) does kill slugs—if applied directly to the slugs somewhere where they cannot access water—but it’s not something that you want to be adding to your garden.

Application is impractical (and unethical to some, like many pest controls) plus, excess salt kills plants, and we do not want more of it in our fresh water systems.

If you’re right there with the slug, it’s easier just to hand pick it.

This explains more about the problem with adding table salt to the garden.

Ammonia

Not Recommended

Ammonia—the stuff you can buy as a household cleaning product—not the actual chemical ammonia, kills slugs if you spray it directly on them. Some people say they use it to drench their soil or apply it to leaves to prevent slugs from eating them.

We couldn’t find any studies that show this works and there are some quick tests online that suggest it doesn’t.

Plus, ammonia, even in a highly diluted form, can burn your plants, animals, and you.

Copper

Effects, If Any, Seem To Be Temporary

Have you seen videos of slugs going up to a strip of copper tape, touching it, and then backing off? It looks promising but apparently this is just a temporary setback.

A study published in 2021 found that “Copper foil only resulted in delayed passage…a reluctance to pass that was eventually overcome.”

Nearly 30 years ago, a different study came to the same conclusion: “The copper strip was capable of delaying the movement of slugs…although after only one hour 25% had crossed the barrier. Sixteen hours later there was no significant difference.”

You can find studies where copper was said to be effective, so maybe we can’t dismiss it entirely, but at best it’s unreliable. There are too many studies where it didn’t make any difference.

So what’s going on when the slug does move away from the copper?

Are they getting some sort of electrical shock as many claim or is something else going on? And if they do, why does the effect seem to diminish over time?

We went looking for scientific sources but could only find articles mentioning the electric shock idea without proper citations. Some reference the use of electrified barriers (mini electric fences to deter slugs) which is quite different from copper tape or wire.

You can learn more about this in the podcast episodes below.

Coffee Grounds

No Evidence

With so many coffee grounds generated each day, no wonder people are always looking for some way to make use of them beyond tossing them in the compost. We wrote about the exaggerated benefits of coffee grounds in the garden here.

The idea to use coffee grounds to deter slugs was given a boost twenty years ago when an article was published in Nature with the heading “Coffee Breaks Slugs.”

However, the research it was referring to wasn’t actually about coffee. It was about caffeine and how a solution of caffeine killed slugs.

Yes, there is some caffeine in coffee grounds and the study showed it didn’t take much caffeine to make a difference, so it’s not completely unrelated, but use of coffee grounds was not studied.

The Nature story claimed the research found that coffee grounds repelled slugs but, when the researchers wrote up their notes, they did not say anything about coffee grounds—they didn’t mention using coffee at all.

So caffeine, however they tested it, has potential, but coffee grounds?

We don’t know. We couldn’t find any studies about coffee grounds and slugs.

You can, however, find lots of videos on YouTube of slugs happily crawling over them.

Eggshells

Nope

I seriously wish I had a dollar for every time I’ve heard some amazing use for eggshells in the garden. We have debunked some eggshell myths here.

For slug control, it is said that you should place crushed eggshells around any vulnerable plants to form a sharp, jagged barrier that slugs won’t cross.

However, that gooey, mucus coating along with a snail’s tough skin serve many purposes and protection from sharp surfaces is one of them.

There are countless photos and videos online of slugs and snails crawling over razor blades, sharpened knives, serrated blades, eggshells, and more—with no signs of distress or damage.

Diatomaceous Earth

Impractical

Diatomaceous earth contains fine, sharp particles but these are rendered useless in moist conditions—the same conditions that slugs and snails thrive in. So, even if it could (somewhat) deter them, application is completely impractical.

This explains why diatomaceous earth is problematic as a pesticide.

Beer

Can Work But May Be Too Impractical

Cheers for a homemade tip that can work!

Using beer to catch slugs is a legitimate, scientifically proven tip.

But, it may not be a practical solution in your garden.

Here’s how it works.

As much as slugs need water to stay hydrated, they are drawn to beer even more. It’s actually the fermentation or the yeast, that’s the real attraction, not the beer per se.

The idea is to put a container of beer out that is easy for the slugs to get in and drink, but deep enough that they can’t get out.

The slug is not dying from drinking the beer but from drowning in the beer—the yeast is just the lure.

In recent years researchers have also found fermented bread dough can also attract them, but they obviously won’t drown in bread so that idea will need some refining.

One early proponent of beer traps was one of my favorite garden writers, Ruth Stout. After hearing a friend suggest the idea, she wrote about it in a column of Organic Gardening and Farming magazine in 1968.

“I remembered that I had once heard (but this was told in a rather joking way) that if you set a pan of beer out in your garden overnight, next morning the container will be full of slugs, either dead or dead drunk. At any rate, they will have had it.”

Ruth said her friend tried it and was thrilled to find it had worked. This got a fair amount of attention, and then, a few years later, we began to get a scientific explanation for how it worked: the yeast in the beer attracts slugs into a container of liquid they can’t escape.

While successful, beer traps pose several challenges:

• Finding a setup the slugs cannot escape from. There are slug beer traps on Amazon if you want to go that route. I’ve never tried them.
• The sun may evaporate the beer, rain may dilute it, or other insects may get into it, so the trap may need frequent monitoring.
• Kids, pets, and other animals should be kept away.

Summary

Slugs and snails play vital roles in nature by recycling dead plant material and animal waste and acting as a food source for a variety of animals. We need them in the ecosystem.

For immediate relief from damage to seedlings or herbaceous plant leaves, hand-pick slugs and create physical barriers to block their access to the affected plants.

Long-term, choose plants suited to your region that support local wildlife that eat slugs.

A pond can also attract slug-loving frogs and toads.

If numbers are high due to a rainy climate, consider changing plant choices or relocating plants to containers that make slug access more difficult.

Be cautious with slug bait products.

• Slug baits containing metaldehyde have been banned in some areas due to known environmental and pet hazards.
• Slug baits containing ferric phosphate used to be recommended for organic gardeners without precautions but we now know those containing chelating agents can harm earthworms.

If you want to trap slugs, lay out a wood board at night where they will congregate underneath or experiment with beer traps.

Resources

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Read More

Rethinking ‘Pests’

• Pests? Gardeners need to rethink how they view slugs, snails and greenfly | theguardian.com

Homemade Deterrents

• Home remedies ‘no deterrent’ against slugs and snails | bbc.com
• Coffee breaks slugs | Nature (research is behind paywall here)

Slug Baits

• Slug killer will be banned across country | telegraph.co.uk.news
• Outdoor use of metaldehyde to be banned to protect wildlife | gov.uk
• Ecotoxicological responses of the earthworm Eisenia fetida to EDTA addition under turfgrass growing conditions | sciencedirect.com
• Chemical confinement of slugs: an alternative to electric fences | oxford academic (paywall)
• Reports of metaldehyde and iron phosphate exposures in animals and characterization of suspected iron toxicosis in dogs | AVMA

Ruth Stout

• Organic Gardening and Farming 1968-01: Vol 15 Iss | archive.org

~Melissa the Empress of Dirt ♛