Oyster shells are a great addition to the garden. Oyster shells will help kill snails and slugs, keep away moles and de-acidify your soil. Since the shells contain calcium carbonate, which is essentially lime, they can raise the pH of acid soils.
Boil water in a large pot. Place the oyster shells in the pot for a few minutes to kill any bacteria.
Take the shells out and let them dry.
Wash and dry your hands to prevent spreading bacteria to the clean shells.
Place dried oyster shells into your plastic bag, push all the air out of the bag and seal the bag shut.
Put a towel over the plastic bag and lay both flat on a stable surface.
Use a hammer to crush the shells until they are in fine pieces.
Keep the towel around the bag and bring it outside to your garden. Spread the fine pieces and mix them into the top layer of soil.
You can also add whole oyster shells in your garden. However, crushing them is more effective.