Caffeine repels slugs but it does not kill them. Unfortunately for it to be really effective you need much larger amounts of caffeine than is in your morning coffee. You can, and some people do, place Used Coffee Grounds around you plants as a barrier. It's great organic nitrogen so it will fertilize them as well. Free UCG are available to gardeners from Starbucks. It's a company policy. Just call up your local Starbucks and ask them to save some UCG for you. Then show up with a 5 gallon bucket and take it away. Remember that in order for this to be truly effective you are going to have to replenish these grounds often. Rain will leach the caffeine out of them and the barrier will be less effective. Still it's a good thing to try and it will help your plants.
Steve
