Coffee Grounds Against Slugs and Snails: Do They Really Work?

Using coffee grounds against slugs is a much-discussed method.

Putting coffee grounds in garden beds is said to help deter slugs and snails.

At the same time, there are reports that state the opposite.

coffee-powder-to deter slugs and snails
Coffee against slugs: Does it work?

How Might Coffee Grounds Work?

Caffeine in large doses is said to be toxic to slugs, and in smaller doses it can slow them down.

It has also been noted that the mere smell of coffee deters slugs and snails.

In addition, others state that ingredients in the coffee grounds stimulate their mucus production.

This would deter them from crawling over.

coffee against slugs and snails
How to apply coffee grounds?

Coffee Grounds in the Garden

Usually, dried coffee grounds are used to form protective barriers against slugs.

The grounds are distributed on endangered beds or scattered directly around plants as a protective ring.

In addition, some supporters of coffee against slugs state that spraying plants with coffee concentrate would protect them from slugs and snails.

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Coffee Grounds: Field Test

It was time for me to look into it and perform our own tests.

So, we dried a lot of coffee grounds, then we spread them in a wide semicircle and placed about 20 different slugs and snails in its center.

What happened next is shown in the following time-lapse recording.

Video: Coffee grounds against slugs and snails | field test

The video shows that some snails, despite the dust-dry coffee, crawl over it with ease.

Some are reluctant, but others make it across the coffee with no hesitation.

You can see that some slugs back away immediately or turn around after coming into contact with the coffee.

However, it is not evident that the smell alone deters the snails.

The claim that caffeine makes the slugs ‘sluggish’ seems also not to be true.

experiment test

However, some tiny slugs did slow down a bit, probably because the coffee grounds were super dry and not because of the coffee itself. Other, larger, slugs did not slow down at all.

So, the experiment shows that coffee grounds are by no means a universal remedy.

Although they work slightly as a repellent, coffee grounds are not effective enough to protect vulnerable plants.

Most of the slugs in this experiment were very young and small.

It cannot be expected that this sort of protective wall will be an obstacle for them once they are fully grown.

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Coffee Powder: Field Test

Some people believe that caffeine is the repelling ingredient.

Since there is less caffeine in coffee grounds than in coffee powder, we decided to give coffee a second chance.

In the following video, you can see the effect of coffee powder on slugs and snails.

Video: Coffee powder against slugs and snails

Unfortunately, this test also showed that coffee does not work well as a repellent.

This time it was even more obvious.

plus minus

Conclusion: Advantages and Disadvantages

The experiments indicate that coffee grounds and powder have little effect on some slugs and snails.

Clearly, they are not enough to protect their favorite foods.

Especially in a large garden with a lot of slugs and snails, it will not be sufficient to put out a daily portion of coffee to repel them.

That would be just too good to be true.

In addition, we expect that rain annihilates any repellent effect, which is the most significant shortcoming of this method.

slug snail coffee grounds

However, using coffee does no harm to the garden; on the contrary, it feeds earthworms, and plants like the minerals contained in the coffee.

In any case, it makes sense to distribute the coffee grounds in the garden, instead of disposing of them on the compost or in the trash.

If you have experience with using coffee as a deterrent, we would be truly grateful for your comments.

Especially if you have evidence for or against its effectiveness.

Literature Reference

Hollingsworth et al. 2002: Caffeine as a repellent for slugs and snails.Link

Whitfield 2002: Coffee breaks slugs – Caffeine kills slugs and snails.Link

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Slug Control: Alternatives

The following might interest you, too:

How to Attract Natural Enemies of Slugs

Slug barriers

Slug Deterrent Paint

Copper Against Slugs

Slug-Resistant Vegetables and Herbs

Slug-Resistant Flowers and Flowering Plants: Perennials and Annuals

Self Made Electric Slug Fence

DIY Slug Control

Runner Ducks Against Slugs and Snails

Peaceful Slug Control & Plant Protection

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9 thoughts on “Coffee Grounds Against Slugs and Snails: Do They Really Work?”

  1. Did you ever try coffee grounds, after running hot water through them? I always thought you were supposed to use your used coffee grounds after you’ve made your coffee. It makes sense to me that there might not be enough caffeine released in coffee grounds right out of the can.

  2. Both (liquid left over coffee) and used coffee grinds work for me. I have to apply every few days (3-4 days), but we drink coffee daily. And to support the comment above (dated July 2020), I tried unused coffee grinds once and it wasn’t as effective. However, used coffee grinds – I rub them on the lower plant leaves, or any leaves that have a way for the slug to access them. IE near a fence that the slugs can climb. I also sprinkle the coffee on any surrounding stones. Orange rinds, I save to place around plants, or fill a piece of an orange rind w/coffee and place around the plant. But what seems to work best (and this is on Hostas and Acuba) is to rub the leaves with the used coffee. AND, we save pickle juice and expired household vinegar to mix in with coffee grinds in small amounts (not to put on the plants, but to splash around surrounding areas where I know they might climb).

  3. I know my mom uses coffee grounds to help make to soil richer but for slugs it has always been egg shells. You do NOT throw any egg shell in the trash at her house,but rather rinse them out & place in a large bowl to dry out. When the bowl gets full you can use whatever is handy another smaller bowl, a plastic cup, anything to crush them up in slivers & tidbits, them sprinkle a descent border around what you don’t want slugs in & so far she’s never had a problem keeping them out of her gardens & flowers.

    • We keep our egg shelves until we use the barbeque. I place the shells on the plate or grill for a short time (careful not to completely burn them) just enough time to dry them out. Remove and crush. They crush much easier after this process.

    • New scientist magazine recommends bread dough for slugs and snails. They find it irresistible. In an experiment bread dough attracted 18,000 in two days! You then gather them up and dispose of them (down the loo? Crush them?)

  4. I have just read the information posted on this site and I have a dear friend that swears by using used coffee grounds and she has had wonderful results. I will also try mixing coffee grounds with dried egg shells and see what results I get. Thank you to all the amazing posts on this site it is very helpful. Thank you, Bella.

  5. I recently moved to live on a ground floor near a stream in Woking. The large slugs here love the smell of coffee. You can see them come out to us when we drink coffee on the terrace and move closer to where are mugs are.

    When I have put used coffee grounds on plants on the terrace, slugs will be positively attracted to the place where the coffee is and go and lie there. I fling them away towards the stram but they keep coming back ti those pots with coffee in…

    This is in contrast to my previous experience in a back garden in New Malden where coffee grounds around my plants seemed to deter the slugs a bit.

  6. The slugs seem to love used coffee grounds in our pots and planters…. So much so that within a few days the entire surface was covered completely in their silver slime… They seem to be addicted to the coffee too!


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