Snails feed on a large selection of crops and landscape ornamental plants, defoliating them and eating their fruits. Mollusks' feeding frenzies can wipe out a gardener's favorite plants overnight, leaving shaggy remnants of stems and leaves. Keeping these pesky snails out of your prized garden isn't difficult and won't take much time (this is true for slugs, too). Slugs are very closely related to snails and cause the same damage; they lack the spiraled, protective shells of snails.
Remove Snail Homes
Eliminate snail and slug hiding places in and around your garden. They include boards, pieces of wood, stones, ground covers, flowerpots and weedy areas that provide dark, moist areas where the creatures rest during hot daylight hours.
Without sufficient cover from the hot sun, snails and slugs will move to a feeding ground with more cover.
Install Snail Barriers
Install copper flashing all the way around your garden, or at the least around individual plants. The flashing needs to be at least 4 inches tall. Bury a 1/2- to 1-inch portion of its height beneath the soil.
Install copper foil around tree trunks and on plant boxes' exteriors. Staple one edge of the foil to each tree trunk, aligning the staple parallel with the trunk to prevent excess damage to the tree. Overlap the foil's edges as you wrap each trunk, and secure the foil in place and to itself with removable fasteners. The University of California Statewide Integrated Pest Management Program recommends using large paper clips that will let the foil expand as the trees grow.
Use the same techniques to cover plant boxes with copper foil.
Fold each piece of foil's bottom edge outward at a 90-degree angle from each tree and plant box to create a lip.
Copper may react with snails' and slugs' mucous, giving the creatures something like an electrical shock.