How to identify and deal with Slugs & snails

Slugs & snails

Gastropoda

Ragged holes and silvery trails on seedlings and soft young growth, worst in damp weather. Use beer traps, wool pellets, or torchlight hand-picking; keep beds clear of daytime hiding places.

Mollusc Leaf-eater Serious SpringSummerAutumnWinter

How to know it

Gray, brown, black or orange slugs from 2 to 15 cm, and banded or brown-shelled snails, all working after dark or in wet weather. The small keeled slugs that live below ground and hollow out potatoes are the ones you never see; the big black slug in the compost is mostly a harmless recycler.

What you'll see

Irregular holes chewed out of the middle of leaves, with the edges left ragged rather than clipped.
Silvery dried slime trails over leaves, soil and paving in the morning.
Seedlings and transplants gone overnight, sometimes with a stub of stem left standing.
Hostas, delphiniums and lettuce reduced to a lace of veins.
Smooth-walled holes and cavities inside potato tubers lifted from wet ground.

Where it comes from

Batches of pearly eggs are laid in soil crevices and under debris almost year-round, hatching in weeks in mild weather. Most of the population lives underground; a garden holds thousands, and both slugs and snails feed whenever it is mild and damp — which now includes much of a British winter.

Damp, mild nights, heavy soils, thick mulches and dense planting. Spring transplants and autumn seedlings take the worst of it; hot dry spells drive everything below ground and the damage stops.

Dealing with it

Go out with a torch on the first mild damp evening after planting — an hour of hand-picking beats everything else in this list.
Set beer traps sunk to the rim, emptied every couple of days, near the plants you actually care about.
Ring vulnerable plants with sharp grit, wool pellets or copper tape, and keep the ring unbroken.
Water in nematodes (Phasmarhabditis) onto warm moist soil for the underground slugs no other method reaches.
Use ferric phosphate pellets sparingly if you must, and never metaldehyde — it is banned, and it poisons the hedgehogs and thrushes doing the job for you.

Keeping it out

Raise seedlings to a good size in pots before planting out; a strong plant outgrows the damage a seedling dies of.
Clear boards, pots, bricks and dense low weeds — the daytime shelter is the population.
Encourage the predators: ground beetles, frogs and toads, hedgehogs, thrushes and slow-worms all work at night.
Water in the morning rather than the evening so beds are drier at slug o’clock.
Grow the martyrs — hostas, delphiniums, lettuce — in pots or protected beds and plant hardier things where damage is chronic.

What it goes for

SeedlingsLeavesFlowersRoots & tubers

Seedlings and soft growth of nearly everything: lettuce, hostas, delphiniums, dahlias, beans, brassica transplants, strawberries and potatoes.

and 374 more in the catalog

Who hunts it for you

Beneficial nematodesSteinernema & Heterorhabditis spp. Microscopic worms watered onto damp soil that hunt down soil-dwelling grubs and release a bacterium that kills them within days. Timing is the whole thing: warm, damp soil and a small target grub, which means late summer for most of what they are used against.
CentipedesChilopoda Flat, fast, one pair of legs to a segment — and a predator, unlike the slow round millipede it is constantly confused with. It hunts slugs, cutworms, springtails and woodlice by night under mulch and stones. Learn the difference and leave this one alone.
Frogs & toadsAnura A resident toad works the beds every night for slugs, cutworms, and weevils. Recruit them with water — even a sunken basin pond — plus damp shade and an upturned-pot toad house; skip the slug pellets that poison their prey.
Garden birdsPasseriformes Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray. Grow to recruit it: Echinacea,Elderberry,English holly,Goldenrod,Rudbeckia,Sunflower
Ground beetleCarabidae Fast, glossy night hunters that patrol the soil surface for slugs, cutworms, and root-fly larvae. Give them daytime cover — thick perennial edges, stepping stones, a log — and skip the tillage that wrecks their burrows. Grow to recruit it: Lavender,Mint,Thyme
HedgehogErinaceus europaeus A European animal, and worth saying so plainly: there are no hedgehogs in North America, and the ally that does the same night shift here is the toad, the opossum or the ground beetle. Where they do occur, cut a gap in the fence and skip the pellets.
Rove beetleStaphylinidae Slim, quick beetles with short wing cases that hunt in soil and litter, taking root-fly eggs and larvae, fungus-gnat larvae, and mites. Mulch and undisturbed ground keep them resident year-round. Grow to recruit it: Mint,Thyme
Salamanders & newtsCaudata Damp-loving hunters of slugs, worms, woodlice and beetle larvae that spend the day under a log or a stone and work the beds at night. Companions to the toads: they want the same damp shade, the same log pile, and the same absence of slug pellets.
Snakes & lizardsColubridae & Phrynosomatidae A garter snake works the beds for slugs and voles and a fence lizard clears grasshoppers off a sunny wall. Almost every snake a gardener meets is harmless and useful; give them a log pile, a warm flat stone and a bit of cover and they stay.