Coffee grounds are good for the soil and good for the hosta. They add nutrients and feed earthworms that aerate the soil. Caffeine does not get rid of slugs. Ask me how I know. LOL Beer attracts slugs and they drown in it when placed in saucers as a slug trap.

I am thinking that I read in National Geographic that caffine was bad for slugs and that they were manufacturing an organic insect repellent from coffee grounds. And that some people pick up the grounds from Starbucks etc for their gardens. Since they are there,I always put my gounds around the hosta . . I have no scientific evidence, but I can't use beer(the dogs drink it) Pouring the coffee on the garden seems expensive. Salt , poured directly on slugs, melts them and small children are entranced by this and perhaps emotionally scared. Oh well . . .

ground up egg shells are a Berlin Wall for slugs and snails

Last year my staff at my Coffee Shop Restaurant gathered "tons" of coffee grinds. I did use it since I had so much...and it was free. I must say that I laid the material at the perimeter of all my gardens and it seemed to work...although it's hard to prove. IMHO, coffee grinds scare the slugs away but slugs are not killed. As for the inside of my gardens I used my traditional ammonia solution which kills slugs on contact.
As for me I'm done with coffee grinds...lots of trouble...etc.
I rather buy Sluggo (here in Canada it's called Baits for Slugs & Snails...this I have proof that once slugs eat the white pellets they will die within a couple of days...I could see their remains which were black and looking just like earth or compost. Sluggo used to be expensive but now here in Canada, price has dropped down to roughly half...so now it's very affordable.

Papou

I don't know how it works- maybe the caffeine just keeps them up all night...but I thought they stay up all night anyways. Here are some links about caffeine repelling slugs:

"Caffeine Used to Fight Slugs and Snails"
http://faculty.washington.edu/chudler/slug.html

"Slugging It Out With Caffeine"
http://www.sciencenews.org/articles/20020629/food.asp

"Caffeine Repels Slugs"
http://news.bbc.co.uk/2/hi/science/nature/2067214.stm

"Snails and Slugs Prefer Decaf"
http://archives.cnn.com/2002/TECH/science/06/26/snails.caffeine/index.html

As far as using coffee grounds, they are reported to be great for composting. Just quite acidic, so you may need to add some lime if you literally throw a "ton" of them on your garden. Don

Sorry I have to chime in here again. Like Papou, I have spread 'tons' of CG in and around my yard. Starbucks has been saving them for me for 5 years now, 25-30 lb. bags, year-round, everytime I pass by. And guess what? I have more slugs now than ever before!

I did my own experiments placing live slugs in various containers of pure coffee grounds, unbrewed coffee crystals, and leftover coffee. Days later they remained unaffected until I sprayed them with 10% ammonia.

Don, I'm perplexed how all those scientific writers are jumping in, saying the same thing with different words, like it's some miracle remedy. It reads great but just doesn't work. As to the acidity of CG, it is neutralized during the brewing process, unfortunately because hosta thrive in lower pH soil.

Thanks everyone for the input, very knowledgeable info and I appreciate it. I will just stick to tried and trued Beer and Ammonia lol.

JoAnn

I tested the coffee and had great success. I tried it because I do not drink coffee it is a free item that I pick up on business trips.

It goes under the rocks around the hostas. I apply in the Fall and in the Spring as soon as the ground warms up.

I had epidemic amount of slugs. This worked so well I am thrilled. It is a plus since it is free. When I saw absolutly not one leaf damaged from these nasty things I became a believer.

Reading the article they do say used grounds would not have enough caffine to be effective, But fresh Maxwell house did the trick. LOL

Sorry others are not gettting the results I got.

Can I point out that when you get grounds from Starbucks or your own home coffeemaker, the caffeine has been leached out of them & been ingested by the drinker? 8-D So there is way less caffeine in grounds than there is in coffee, or in the unbrewed grounds.

Coffee grounds are terrific composting material & loads of people spread them all over their gardens do the delight of their plants, but don't look for help against slugs or anything else, from caffeine in brewed grounds.

Read the paper, Slugging It Out with Caffeine"from Science News as posted above by don r.

This spring, I am going to try the unbrewed coffee, just as marquest says!

You have plenty of research but there is a study done in Hawaii the proves that caffeine repels slugs but as others have noted the test was not done with spent grounds.

I'm running test using coffee grounds as a weed barrier in pots and it works well for that purpose. Last year I checked many of those pots and found slugs crawling right across the grounds to get to the hosta.

I collected some of those slugs and put them in containers with used coffee grounds and spent grounds and they avoided the grounds in the bottom of the container but did not die.

It may be that they are not bothered by dry coffee grounds.

I can say that they are not a solution for slugs.

Papou, has the solution with 10% ammonia spray and I add if he doesn't say so to spray the soil around the plants during the day to kill the little buggers where they hide. You can spray them on the plant at night but that doesn't kill the ones waiting to crawl on tomorrow night. Ammonia is a contact killer and does not harm the plants if you don't over do it but does kill everyone when you saturate the soil around the plants.

there is this great Youtube video of 're-caffeinated' used coffee grounds successfully repelling a slug, its a time lapsed video of it really working taken over a 3 day experiment.

I was a nay-sayer until I saw this. Finally we have some real solid evidence proving it works.

However, should be mentioned that it is treated coffee grounds, which apparently has a higher caffeine content..

click on the helpful link or copy and paste this one below..
http://www.gardenrobusta.com/storepage379759.aspx

Here is a link that might be useful: Sped up Youtube video footage of coffee grounds repelling slugs