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.
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.
The Latest Science
The latest testing found that bread dough and bread dough slurry were the best attractant for various species of slugs and snails. It was more effective than beer.
Getting Rid of Slugs and Snails
There are all kinds of methods for getting rid of snails and I have reviewed several of these including:
- Eggshells Control Slugs – Do They Really Work?
- Getting Rid of Slugs With Coffee Grounds
- How To Get Rid of Slugs With Beer
- How to Get Rid of Slugs With Copper
- How to Get Rid of Slugs with Diatomaceous Earth
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: https://www.gardenmyths.com/getting-rid-ants-coffee-grounds/#more-1854
4) Do Beer Traps Kill slugs: https://www.gardenmyths.com/do-beer-traps-kill-slugs/#more-1784
5) Does Copper Repel Slugs: https://www.gardenmyths.com/copper-repel-slugs/#more-1249
I read somewhere that wood ash deterred slugs so I tried putting it in my flower bed around the Dalias. Seem to work like a charm! The big problem with that is it every time I water it washes the ash into the soil and I have to reapply. It also is not very pretty. But it did keep away the Slugs.
It will also make your soil more alkaline.
Caffeine is an insect repellant, which is why some plants produce it in the first place. There is some caffeine left in used coffee grounds.
What I don’t know is whether or not caffeine repels slugs. They’ve not started attacking my tea plant, but I’ve not been growing it for long.
I use fresh warm urine to control slugs every night I sprinkle it liberally around the garden!
I doubt that works, but if you have a reference showing it does – I’d like to see it.
So have you found any ways that actually work to deter slugs? They are tearing up my garden!
Commercial slug bait – fairly safe and works well.
I’d recommend against the kind certified as “organic.” I was using some (Sluggo brand) for a while to control slugs. I didn’t see the empty snail shell I had seen using non-certified snail and slug bait (hereinafter “real” snail bait”) previously, but I thought I didn’t have a snail problem. I also didn’t see dead slugs, but I don’t monitor carefully enough to see those before the ants eat them.
So, one day I ran out of the “organic” stuff. I dug up some of the good old Corry’s Slug and Snail Death from the back of a cabinet. Whaddaya know? It turns out I did have a snail problem and using the “real” Corry’s snail bait, I got plenty of empty snail shells. I’ve been using Corry’s and similar store-brand products ever since. It seems to be working better, although it turned out that bird netting was required to prevent some damage that I had thought was caused by slugs.
Side rant: I believe that to be certified “organic” the only criterion is that it must have been in use in about 1850 before evil scary technology and products tested and proven to be effective started coming on the market. Don’t even get me started on copper sulfate being considered “organic” in the not-scary sense. Copper sulfate is a inorganic chemical (using the word “organic” in the sense that it is used in chemistry) and doesn’t biodegrade. The copper, being an element, just doesn’t stop being copper, remains toxic, and accumulates in the soil. Not good. The scary “chemical” (in the hysterical sense) fungicide I have also used is not certified “organic,” although it is an organic (carbon-containing) chemical, but when it hits the soil it binds to it and degrades fairly quickly. It does not accumulate in the soil from year to year, like the copper stuff. Unfortunately, it requires real attention to control curly leaf on my peach and nectarine trees. If I don’t succeed this winter, I will cure the problem once and for all by replacing the trees with some citrus.
Can you compare the active ingredients in the two products? Without that a comparison does not tell you very much.
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?
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 ?
No, new to me.
I understood it make them hyperactive and they die in a day or so
Where is the reference?
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.
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.
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!
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.
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
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.
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.
I am not assuming that at all. If you think the experiment is flawed then you need to explain why.