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Getting Rid of Slugs with Coffee Grounds

In the two previous posts I looked at ways to use Coffee Grounds in the Garden and the effect of coffee grounds on ants. There was one outstanding question that did not get resolved. Do coffee grounds deter slugs from eating your plants? Since I could not find any scientific work on this topic I decided to run some tests myself.

slugs and coffee grounds

Photo Source: All About Slugs

How to Get Rid of Slugs

The claim that coffee grounds will kill slugs was discussed in a past post–they don’t. What was not clear is whether coffee grounds prevent slugs from reaching your plants. Do slugs hate sliding on the grounds so much that they will not cross a barrier of coffee grounds on the ground? If slugs do not cross a barrier of grounds, then it might be a good way to keep them from your plants.

For other common ways to get rid of slugs see the reference list below.

Experiment Setup

I set up a plastic tub with moist soil on the bottom. I collected 3 slugs. For some reason I have very few slugs in the garden this year so the test was limited to these 3 lucky molluscs. I added some plant leaves that had been eaten by slugs, so I knew they liked the leaves. Everything was left for 2 days to let the slugs get accustomed to their container, and to make sure they did not mind sliding around on the soil. They seemed to be quite happy, moved all over the container and ate some of the leaves.

On day three, a 2 inch wide, 1/4 inch deep, circle of coffee grounds was placed on the soil. Some plant leaves and the 3 slugs were placed inside the circle. If the coffee grounds work, the circle should keep the slugs inside the circle. The wait begins…..

Test Results

It was not a long wait. Slug #1 slid up to the grounds, and without any hesitation, crossed the grounds and was out of the circle in about 10 secs. Who says slugs are slow! Slug #2 did the same and was free in 20 secs. Slug #3 decided to have a nap, and crawled under a leaf. It never went near the grounds.

The slugs were returned to the center of the circle to repeat the test. The same thing happened. Two slugs left in less than a minute, and the third stayed put.

Conclusions

It is clear that slugs do not mind walking on the coffee grounds. The myth that coffee grounds stop slugs is busted!

To be fair, I only tried this with 3 slugs, and they were of one type. Other species of slugs might behave differently. But given the speed at which my slugs crossed the barrier, I would be surprised if the physical characteristics of the grounds would stop any slug.

The above test was done with wet coffee grounds. Would dry ones work better? Maybe, but how long would they stay dry laying on soil?

References:

1) a good source for facts about slugs: http://www.slugoff.co.uk/slug-facts/facts

2) All About Slugs: http://www.allaboutslugs.com/how-to-identify-slug-or-snail-damage/

3) Getting Rid of Ants with Coffee Grounds: http://www.gardenmyths.com/getting-rid-ants-coffee-grounds/#more-1854

4) Do Beer Traps Kill slugs: http://www.gardenmyths.com/do-beer-traps-kill-slugs/#more-1784

5) Does Copper Repel Slugs: http://www.gardenmyths.com/copper-repel-slugs/#more-1249

Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

16 Responses to 'Getting Rid of Slugs with Coffee Grounds'

  1. Sheva says:

    Coffee grounds did work for me
    I feel the need to share my own experience with this as I’ve been very happy with my hosta plants lately. I’ve been battling slugs since the hosta sprouted out or so ago. I’ve used diatomaceous earth to no avail. I really hate to use salt as I’m sure it causes them pain, but that’s what I’ve been using every evening to save my plants. I thought, there’s no way to have to kill them everyday so I was open to just about anything laying in the house. Without expectations, I took a couple of handfuls of unused community coffee grounds and sprinkled them around the hosta plants. It has been 2 days and the new leaves have not a single hole in them.
    The slugs in my garden does not look like what Pavlis has, so he may be correct in the sense that some reaction depends on a certain species of slugs.
    My point is, even as you read discouraging write- ups such as certain methods do not work, it doesn’t hurt to still try because every garden environment along with its habitats differ from one another.

    • “It has been 2 days and the new leaves have not a single hole in them.” – that is not long enough to reach any conclusions. Where are the controls?

  2. Azza says:

    Here in the UK they sell pellets of discarded wool as material to cover the soil in the plant pots so that it constitutes a barrier. It seems to be efficient although I did not try a real controlled experiment. Have you heard of this ?

  3. deb says:

    I understood it make them hyperactive and they die in a day or so

  4. JEAN ALBAUGH says:

    What about salt to kill slugs?

    • It does work as far as I know. But you need to find them, then shake the salt onto them. Good luck finding them all in the night.

      And table salt is not good for plants.

  5. Tarjei T. Jensen says:

    Hi,

    You did not say anything about the condition of the coffee grounds.

    The stuff I have read says that there has to be coffein left in the coffe grounds for it to work.

    I would have preferred if you made the experiment with new coffe as well to see if it matters.

    • Feel free to redo the experiment. I don’t see the point of trying it with new coffee since people are not going to buy new expensive coffee to combat slugs. the whole idea of using grounds is that it is a ‘free’ waste product.

      You can argue that there is always some coffee in grounds. No one makes coffee and extracts 100% of the coffee.

    • Kingston says:

      Let me try answer some thoughts u guys are questioning here .. I’m not trying to get rid of slugs .. So let me tell u how I get to this linked about using coffee ground and Maybe it might answer some of the questions ..Actually I want to get rid of mosquiris flying around next to me door. So my cousin tell me to use some coffee ground and put around my house. So my wife decide to do so and out it outside the door. Yes I didn’t see much mosquitos flying around while I have a smoke. Then I realize there’s a few slugs In every cup of coffee ground .. And my house and the weather was pretty dry here tonight and I often see slug around where i live .. But I do have a front yard. So I try to search doe coffee ground attract slugs and I got into this link. So What I’m trying to say here is coffee ground attract slugs Instead get rid of it. Slug wasn’t in my mind when I first try to use coffee to get rid of mosquitos. But all sudden I attracted a lot of slugs in those coffee ground!

      • Kingston says:

        There’s some words i write it wrong .. The whole point I’m saying is coffee ground don’t get rid of slugs it actually attract them .. House I live here is pretty dry and I don’t often see slugs but ever since my wife put it out there. They start showing up and then I started to research. I Google “does coffee ground attract slug”? and here I am seeing u guys debating.. End of my story.

  6. Inger Knudsen says:

    I think I have had good results with sand around plants, not a puny little circle but a serious 50 cm circle. Why would a little circle deter them? They need to get dried up when they cross, otherwise it makes no sense, also coffee is wet,soft and yummy. Sand is desert, hard and dead. I have never heard about coffee grounds as a slug deterrent only as a nice soil amendment

    • Robert Pavlis says:

      When the slug starts crossing the material it does not know how wide it is so a narrow or wide circle should not make a difference to having them start the crossing. If the material dries them out, or kills them during the crossing then it is effective by killing them.

      • Diana says:

        You are assuming slugs can’t see beyond 1/4 inch in front of them and that they don’t use other senses when traveling. Your experiment is seriously flawed, sorry to say.

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