Slugs and snails feed at night on mild, damp evenings, and a damp climate keeps them active through much of the growing season. Here is what they look like, how to tell if they are the ones eating your plants, and which controls have been tested and which are repeated folklore.
What does it look like?
Soft-bodied invertebrates covered in mucus, with four tentacles. Snails can retreat fully into their shells, while slugs have tiny shells hidden under the skin. There are over 44 slug species and 90 snail species in the UK, which can be hard to tell apart; netted field slugs, brown soil slugs and common garden snails are the most likely culprits, and keeled slugs can tunnel into potatoes and other tubersA swollen underground stem or root a plant uses to store energy, which can also grow into a new plant, the classic example being a potato. Full definition →.
What causes it
Damp, mild conditions are what bring them out: most feeding happens on mild, moist evenings, which is also when a torchlight search finds the most. Evening watering makes conditions more favourable for them overnight, which is the reasoning behind watering in the early morning instead.
🌱 Plants at risk
- Potatoes
- Kale
- Beetroot
- Courgettes
- French Beans
- Peas
- Lettuce
- Spinach
- Broccoli
- Cabbage
- Strawberries
- Swede
- Turnip
- Cauliflower
- Kohlrabi
- Calabrese
- Pak Choi
- Celeriac
- Shallots
- Spring Onions
- Radish
- Jerusalem Artichoke
- Runner Beans
- Chard
- Rocket
- Endive
- Celery
- Cucumbers
- Sweetcorn
- Squash
- Pumpkins
- Asparagus
- Rhubarb
- Fennel Bulb
- Thyme
- Dill
- Coriander
- Lovage
- Sorrel
- Borage
- Angelica
- Globe Artichoke
- Sea Kale
Symptoms
They feed at night, leaving ragged holes in soft leaves and seedlings, with slime trails as the giveaway sign. Seedlings and soft-leaved plants are hit hardest.
Controls: what works
Not every method here works equally well: some are backed by real evidence, some are simply traditional, and a few have been tested and shown not to help despite how often they get repeated.
Biological control: nematodes watered into the soil
The RHS and Garden Organic both describe the slug nematode (Phasmarhabditis hermaphrodita) as an effective biological control, specific to molluscs.
Nematodes affect all slug species, including the beneficial ones that don't feed on live plants, so use them in a targeted way. Snails are unlikely to be affected.
They are effective but can be expensive to buy.
Conditions: Needs moist, warm soil at 5 to 20C, so spring to early autumn is the best time to apply. A single application works for around six to eight weeks, and the soil should be kept moist for at least a few weeks.
Cultural controls: hand-picking on torchlit evening searches, transplanting sturdy plants rather than seedlings, choosing resistant plants, encouraging natural predators
The RHS's approach now that pellets are advised against: choose less palatable plants (woody ones, and those with thick or waxy leaves), transplant sturdy potted plants rather than young seedlings and use clochesA small, portable clear cover placed over an individual plant or short row to trap warmth and keep off wind, rain and pests. Full definition →, hand-pick on mild, damp evenings and relocate the slugs away from your plants, water in the early morning rather than the evening, and encourage birds, frogs, toads, hedgehogs, slow-worms and ground beetles.
Barriers: crushed eggshells, bark mulchA layer of material spread over the soil around plants to suppress weeds, retain moisture, and improve soil structure as it breaks down. Full definition →, wool pellets
Many popular barriers lack scientific support. An RHS study found that bark and similar barriers did not reduce slug damage in a garden setting.
These are among the most repeated pieces of gardening advice in Britain, and the RHS study found no benefit.
Barriers: copper tape and sharp grit / gravel
The RHS found no reduction in slug damage from copper tape in a garden setting, while copper tape is listed as useful around pots and the legs of greenhouse staging (Garden Organic).
The two are not equally weighted: one ran a study and reported a negative result, the other lists copper tape without citing one. Garden Organic's advice is for pots and staging, which is a different setting from an open bed.
Slug pellets containing ferric phosphate
Earlier position: RHS trials found organic (ferric phosphate) slug pellets performed as well as those containing metaldehyde, as reported by Garden Organic.
Current position: The RHS advises against slug pellets altogether: 'No – slug pellets (even organic ones) have been shown to have negative effects on wildlife in the garden.' Garden Organic's slug advice also says to avoid the so-called organic pellets, which are ferric phosphate-based.
Both can be true. The earlier trials measured efficacy against slugs; the current advice is about harm to wildlife. A pellet can work and still be a bad idea.
Beer traps
Hollowed-out citrus skins or jars of beer sunk into the soil can catch slugs and should be emptied regularly. No trial of how well they work was found.
Natural predators of slugs and snails
These 5 creatures eat slugs and snails, and each has a page on how to get more of them in your garden: what to plant, or what to order and when.
Scottish grower notes
Slug control is a difficulty for organic growers in Scotland. Fields with low slug populations should be chosen, particularly for late, overwinteredKeeping a plant alive and intact through the cold months, whether left outdoors, moved under cover, or stored dormant. Full definition → crops, which are at high risk.
Myths about slugs and snails
“Traditional blue metaldehyde slug pellets are still fine to buy and use in UK gardens.”
Metaldehyde slug pellets were withdrawn from sale in the UK from 31 March 2021, and it became illegal to sell or use existing stock from 1 April 2022. The decision followed advice from the UK Expert Committee on Pesticides and the Health and Safety Executive that metaldehyde poses an unacceptable risk to birds, mammals including hedgehogs, and other wildlife exposed to treated slugs, soil or water. Ferric phosphate is now the only slug pellet active ingredient legally available in the UK.
What to do: Check the label before buying pellets: only ferric phosphate (sometimes listed as iron phosphate) products are legal. Any pellet claiming to contain metaldehyde should not be used and, if you find old stock, should be disposed of rather than applied.
1 source
- Garden OrganicMetaldehyde slug pellets were banned from sale and use in the UK from 2021 to 2022 because of documented harm to dogs, birds and hedgehogs, and ferric phosphate pellets are now the legal alternative.
“Ferric phosphate (iron phosphate) slug pellets are completely safe for hedgehogs, birds and other garden wildlife.”
Ferric phosphate pellets are approved for organic growing and carry far less risk to mammals and birds than the now-banned metaldehyde formulations. However, they are not treated as risk-free: even organic slug pellets have been shown to have negative effects on wildlife in the garden (RHS), and Garden Organic advises avoiding the so-called organic pellets, which are ferric phosphate-based.
Our read The gap between ferric phosphate and metaldehyde is real, but "safe" overstates it: these are still pesticides with some non-target impact.
What to do: Lean on the non-chemical controls first: choose less palatable plants, transplant sturdy plants, hand-pick on damp evenings, and encourage predators. The RHS advises against using pellets at all.
2 sources
- RHSSlug pellets, including organic ferric phosphate ones, have been shown to have negative effects on garden wildlife, and the advice favours encouraging natural predators and other cultural controls instead.
- Garden OrganicSo-called organic slug pellets are ferric phosphate-based, and the advice is to avoid them.
“Every slug or snail you find in the garden is a pest eating your plants, so the more you kill on sight, the better.”
The UK is home to over 44 slug species and 90 snail species, but only a handful regularly feed on living garden plants, including the netted field slug, brown soil slug and common garden snail; most others mainly recycle dead plant material and are themselves food for birds, hedgehogs and frogs. Oregon State University Extension makes the equivalent point for its region: several native slug and snail species found in gardens do not damage garden plants at all.
What to do: Focus control effort on seedlings and soft new growth, where the actual plant-feeding species cause the most damage, rather than treating every slug or snail in the garden as a threat to be destroyed.
2 sources
- RHSOf the UK's many slug and snail species, only a small number such as the netted field slug, brown soil slug and common garden snail regularly damage garden plants, while most are beneficial decomposers and prey for garden wildlife.
- Oregon State University ExtensionSeveral non-native slug and snail species cause garden damage, but native species such as banana slugs and Pacific sideband snails do not damage garden plants.
“Sprinkling used coffee grounds around plants repels or kills slugs”
A Washington State University Extension fact sheet on coffee grounds finds no evidence that they repel or kill garden pests. Dry grounds don't reliably deter slugs, and damp grounds can even add surface moisture and organic food that draws them in. Caffeine itself is toxic to slugs, but only at concentrations from a liquid drench, not from scattering used grounds.
What to do: Don't rely on spent coffee grounds as a slug barrier. Use tested non-chemical methods (physical barriers, nematodes, encouraging predators) instead.
1 source
- WSU Extension — Using Coffee Grounds in Gardens and LandscapesThe fact sheet finds no evidence that coffee grounds will repel or kill any garden pests.
“Slugs and snails only come out and feed at night, so checking plants during the day won't reveal a problem.”
Slugs and snails are predominantly nocturnal, and most feeding does happen after dark, which is why torchlight checks in the evening are the standard way to find them in the act. But extension research adds an important exception: Colorado State University Extension notes slugs occasionally stay active on overcast or rainy days, not only at night.
Our read Night is the main feeding time, so evening checks find most of them, but the claim fails because daytime activity on overcast or wet days is reported.
What to do: Do your main slug and snail patrols after dark or at first light, but also check likely daytime hiding spots (under pots, boards, mulch, dense foliage) on cool, overcast or wet days, when slugs may still be moving and feeding.
3 sources
- RHSSlug feeding mainly happens at night, so slime trails and leaf damage found in the morning are usually the first evidence, and torchlight searches after dark are recommended for hand-picking.
- Oregon State University ExtensionSlugs feed at night when temperature, wind and humidity are favourable, and retreat to dark, moist hiding places such as under mulch and leaves during the day.
- Colorado State University ExtensionSlugs feed mostly at night, although they occasionally are active on overcast or rainy days.
“Hand-picking slugs and snails off plants, especially by torchlight in the evening, makes a difference.”
Extension services list hand-picking as one of the more reliable non-chemical controls, provided it is repeated regularly rather than done once. Oregon State University Extension recommends checking plants about two hours after sunset or in the early morning with a torch, and trapping slugs under boards for daily removal.
What to do: Patrol vulnerable beds after dark or at first light several times a week during mild, damp weather, and dispose of collected slugs in soapy water rather than tossing them over the fence, where they can simply return.
2 sources
- Oregon State University ExtensionHand-picking slugs about two hours after sunset or in the early morning, along with trapping them under boards for daily removal, is recommended as a control method.
- RHSTorchlight searches on damp evenings are recommended as a hand-picking method for controlling slugs and snails.
“Slug and snail damage gets noticeably worse after rain or during extended wet spells, so that's when to watch plants most closely.”
Slug and snail movement and feeding both depend heavily on moisture. Colorado State University Extension notes that slug population levels track a garden's moisture conditions directly, and Oregon State University Extension times its recommended start to slug control to autumn, after the first seasonal rains begin, because slugs need damp conditions to move about and lay eggs.
What to do: Step up monitoring and hand-picking in the days after rain or during prolonged mild, wet spells, since that is when slugs are most able to travel and feed; dry spells give plants more of a breather.
In Scotland: Scotland is generally wetter than much of England, so the wet-weather vigilance window may run longer, though no source measures it.
2 sources
- Colorado State University ExtensionThe level of a slug population depends on the moisture conditions in a garden, and slugs are occasionally active on overcast or rainy days.
- Oregon State University ExtensionSlug control efforts are recommended to begin in autumn once the first rains arrive, because slugs and snails lay their eggs and become more active as the rains begin.
Frequently asked questions
What should I do first if I find slugs and snails in my garden?
The first thing to try: Biological control. Then: Cultural controls.
Will slugs and snails kill my plants?
They can cause serious damage if left unchecked. Start with the research-supported controls above and you will get a crop.
Are there any common slugs and snails remedies that do not work?
Yes. Barriers have been tested and found not to reduce damage. See the “tested, does not work” entries above for the studies.
Should I just leave slugs and snails alone?
In most gardens, yes. Slugs and snails are food for birds, wasps and predatory insects, and a healthy garden carries some without trouble. Tolerance is also RHS's position, for that same reason.
Sources
Show the 5 sources
- RHS1: slugs as a gardener's friend, 44 slug and 90 snail species, likely culprits, copper tape and bark not reducing damage, advice against all pellets, hand-picking, less palatable plants, transplanting sturdy plants, early-morning watering, predators, nematode conditions (5 to 20C, spring to early autumn) and effect on all slug species, citrus-skin and beer traps
- Garden Organic8: copper tape around pots and greenhouse staging; grit or granules; checking barriers daily; hand collection; attracting ground beetles, frogs, toads and birds; slug-resistant potato varieties; avoiding ferric phosphate pellets
- Garden Organic8: nematodes effective but expensive, soil above 5C, working once for around six to eight weeks, keep the soil moist and warm
- Garden Organic8: RHS's EARLIER position on organic pellet efficacy, cited to document the stance change
- SAC/SRUC13: slug control a difficulty for organic growers in Scotland; fields with low slug populations should be chosen, particularly for late, overwintered crops which are at high risk (SAC Technical Note 488, 2000, field-scale organic vegetables)