Caffeine kills slugs and snails. ... Coffee grounds are already recommended as a home remedy for keeping slugs and snails at bay. Grounds repel slugs, Hollingsworth found, but a caffeine solution is much more effective, he says: "Slugs turn back immediately after contacting the [caffeinated soil]."

Will coffee grounds keep slugs away?

When using coffee grounds, moderation is advised. A study in June 2002 reported in the journal Nature found that slugs and snails are killed when sprayed with a caffeine solution, and that spraying plants with this solution prevents slugs from eating them.

How do you use coffee grounds for slugs?

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.