What do snails eat

What they eat, and why you never see them doing it

Slugs and snails eat almost anything soft and green: seedlings, hosta and lettuce first, then strawberries, brassicas, marigolds, potato tubers and any fruit lying on the soil. What they cannot manage well is anything tough, hairy, aromatic or leathery, which is why lavender, yarrow, salvia and ferns sit untouched beside a hosta that has been reduced to stalks.

They also eat a great deal that is not your plants at all: decaying leaves, compost, fungi and other soft debris. In a garden with plenty of that, they do real work breaking it down. They only become a problem when there is a bed of seedlings within crawling distance.

The reason they seem invisible is that they feed at night and shelter through the day under pots, boards, mulch and low foliage where the air stays damp. By morning the animal is hidden and only the damage is left, which is why so many people assume something else did it.

The diet in detail

Since this is the question the page is named for, it is worth answering fully rather than in the one line that the damage requires.

What they prefer in a garden

Extension lists converge on a recognizable group: hostas, violets, ageratum, lilies, cleome, strawberries, lettuce and cabbage, with cucumbers, tomatoes and wilting lettuce leaves named repeatedly as favorites. The pattern behind the list is more useful than the list itself. They go for soft, low, moist, tender tissue, which is why seedlings are eaten whole and why a mature plant of the same species is only grazed at the edges.

The damage is large ragged holes rather than neat ones, and young seedlings disappear entirely. Slime trails on the leaf or the soil confirm it.

What else is on the menu

Living plants are the part gardeners see, and they are a minority of what these animals actually eat.

• Decaying plant material. Leaf litter, spent foliage, compost and the general debris of a garden floor. Shelled snails in particular prefer rotted material to fresh.
• Fungi, including the fungal threads running through leaf litter and soil.
• Soil itself, along with the bacteria and minerals in it.
• Carrion, and in some species earthworms and sowbugs.
• Other snails and slugs, and their eggs. The common garden snail eats the eggs of other gastropods, and some species eat other snails outright.

That last one is worth pausing on. Part of the population is feeding on the rest of it, which is one of several reasons a garden cleared of everything with a broad treatment often ends up with more of them, not fewer.

Calcium, and why it explains the behavior

A snail has to build a shell, and shell is calcium carbonate. Calcium is a requirement of the diet rather than a preference, and it drives behavior that otherwise looks inexplicable. The giant African land snail is documented eating stucco off houses to get it. On a smaller scale it is why snails congregate on old mortar, concrete, and lime-rich soil.

It is also the honest reason eggshells fail as a barrier: crushed shell is calcium carbonate, which is the thing the animal is looking for. Whatever the sharp edges are supposed to do, the material itself is not a deterrent.

The diet changes as they age

A detail that explains a common observation. Older, larger snails feed less on living plants than intermediate-aged ones do, shifting toward scavenging leaf litter and decomposing material. The heaviest damage to a bed therefore comes from the middle of the population rather than from the biggest animals in it.

The practical consequence runs against instinct: removing the large conspicuous snails is the least useful thing you can do, because they are doing the least damage and, in doing it, are competing with and sometimes eating the ones that are. Timing the search for two hours after dark, when the whole population is out, does far more than picking off the obvious individuals by day.

Are snails bugs?

No, and this is not a pedantic point. It is the single most useful fact on the page, because it decides what will and will not work on them.

Snails and slugs are molluscs, in the phylum Mollusca alongside scallops, squid and octopus. They are more closely related to an octopus than to any insect. They have no exoskeleton, no six legs, no jointed limbs, and no insect nervous system for a pesticide to act on.

Insecticides therefore do nothing to them. A general garden insect spray applied to a bed with a slug problem kills the ground beetles that were eating the slugs and leaves the slugs untouched, which is a net loss twice over. What works is a molluscicide, a different class of product, and the two available to home gardeners are iron phosphate and metaldehyde baits.

The practical difference between a slug and a snail, beyond the shell, is where they can go. A slug has no shell to accommodate, so it moves through soil and into crevices a snail cannot enter, and it survives underground through weather that would drive a snail to seal itself up under a pot. That is why slug damage often appears on plants with no obvious hiding place nearby.

Apple snail eggs

A separate animal and a separate problem, and worth knowing because the response is the opposite of ignoring it.

Apple snails are large freshwater snails, not garden snails. Several species live in the southeastern United States, one native and the rest introduced, and the introduced ones are seriously damaging: the island applesnail eats rooted aquatic vegetation, and a single snail can produce as many as two thousand eggs every two weeks. They are difficult to tell apart by the shell, since the invasive island applesnail reaches about 5 inches and the native Florida applesnail 2 to 3, and sizes overlap in between.

The eggs are the reliable identification, and the color is the whole of it. Apple snails lay their eggs in masses above the waterline, stuck to plant stems, walls and other hard surfaces at the water’s edge. Submerged eggs do not hatch.

• Bright pink egg masses are the invasive ones. They fade toward white or gray shortly before hatching.
• White egg masses belong to the native Florida applesnail and should be left alone. That species feeds on algae rather than on plants, and it is the principal food of the Everglade snail kite.
• Green egg masses belong to the spike-topped and titan applesnails.

UF/IFAS guidance on pink masses is direct: scrape them off into the water, where they will not hatch. The same guidance is emphatic that only pink masses should be scraped, because destroying native white ones removes a food source for an endangered bird. If you are not certain, photograph it and ask a local extension office rather than guessing.

The other half of the advice is about how they arrive: do not release unwanted aquarium animals into local waterways. Every established population of these snails started that way.

Making sure it is them

The signature is irregular holes chewed out of the middle and edges of leaves, often with a silvery slime trail nearby that catches the light. Caterpillar damage looks similar but leaves droppings and no slime; flea beetles leave small round shot-holes; and rabbit or deer damage removes whole stems cleanly.

They also climb. It is worth knowing that slugs will go to the top of a mature plant to feed, so damage well above ground does not rule them out.

The confirmation is a torch after dark. Two hours after sunset, especially after rain, is when a bed that looked empty all day turns out to be busy.

What actually works, in order

1. Hand-pick at night

   The most effective method there is. Go out with a torch and drop them into soapy water. Unpleasant, free, and it removes breeding adults rather than suppressing a population.

2. Trap them under a board

   Lay pieces of cardboard or plastic on the soil. They crawl underneath by morning and can be lifted and collected in one go, which turns a night job into a day job.

3. Beer traps, sunk to the rim

   A container buried so the top is level with the soil, filled several inches deep with beer or a water and yeast mix. They are drawn by the smell, fall in and drown. Check and refill several times a week or they stop working.

4. Iron phosphate bait where damage is heavy

   A stomach poison that damages their digestive system. Oregon State’s research found it effective, lasting about two weeks even after it gets wet, with feeding stopping within days and death taking up to a week. It is the option that does not pose the problems around children and pets that older baits do.

5. Take away the daytime shelter

   Boards, pots, thick mulch against stems and dense low growth are where they spend the day. Clearing that around vulnerable beds does more over a season than any single treatment.

Timing, which most people get wrong

The instinct is to act in midsummer when the damage is visible. Oregon State’s point is that autumn and spring are the prime times, because that is when the adults are active and laying.

Killing one slug in spring removes the several hundred eggs it would otherwise have laid. Killing one in July removes one slug. The same effort spent in the right month is worth many times more.

What does not work

Salt kills the individual animal and damages the soil, and it does nothing about the ones you did not find. It is a way of feeling effective rather than being effective.

Copper tape, crushed eggshells, coffee grounds and sharp grit all have devoted followers and thin evidence. They may slow an animal down at a barrier; none of them clears an infestation, and eggshells in particular are one of the most repeated pieces of garden advice with the least behind it.

Metaldehyde baits do work and are genuinely dangerous to dogs, cats and wildlife. Where a bait is wanted, iron phosphate is the one that does the job without that risk.

Living with them

Complete elimination is not a realistic goal in a garden with any moisture in it, and it is not a useful one either, since they process a lot of dead material.

What is realistic is protecting the plants that actually suffer. Seedlings and hosta get the effort; established shrubs and anything aromatic do not need it. Watering in the morning rather than the evening leaves the surface drier at nightfall, which is when it matters, and that one change costs nothing.

Frequently asked questions

What do snails and slugs eat in a garden?

Soft green growth first, so seedlings, hosta, lettuce, brassicas and strawberries, along with fruit resting on soil. They also eat decaying leaves, compost and fungi, which is useful work. Tough, hairy or aromatic plants such as lavender, salvia, yarrow and ferns are largely left alone.

How do I know it is slugs and not caterpillars?

Irregular holes plus a silvery slime trail means slugs or snails. Caterpillars leave droppings and no slime, flea beetles leave small round shot-holes, and rabbits cut stems cleanly. A torch two hours after dark settles it.

Do beer traps work?

Yes, within a small radius. Sink the container so its rim is level with the soil, fill it several inches deep, and check and refill it several times a week. It is a supplement to hand-picking rather than a replacement.

Is slug bait safe around pets?

It depends on the bait. Iron phosphate is the less toxic option and does not pose the problems that metaldehyde does around children and pets. It works slowly: feeding stops within days and the animal dies over about a week.

Do eggshells and coffee grounds work?

Not reliably. They are among the most repeated pieces of garden advice with the least evidence behind them. Hand-picking at night, removing daytime shelter and treating in spring and autumn are what actually reduce numbers.