I would not put the coffee grounds down thickly, it makes water not able to penetrate if applied heavy, I sprinkle it around
in a fair but not heavy amount. I was not doing it as a slug deterrent, but as nourishment for my rose garden and in my compost
to attract worms. Luckily so far no slug problem in my Hostas but as a preventative put jagged egg shells around and was
surprised to see that mt Rat Terrier was eating them, but has since lost interest.
