Slugs and snails
The most destructive garden pest in a wet British spring, and the one surrounded by the most confidently repeated advice that does not work. They shred seedlings overnight and leave irregular holes with slime trails nearby.
Caused by: Deroceras reticulatum, Arion species, Cornu aspersum and others
Described view
Strawberry foliage showing two kinds of damage in one frame: large irregular holes rasped through the leaf blade with a silvery slime trail still visible across the leaf, and separately the neat semicircular notches bitten inward from the leaf margin that are the signature of adult vine weevil
What brings it on
Damp, mild conditions and overnight activity. Damage concentrates on soft young growth and on newly planted-out seedlings, which is why the same plant is vulnerable for about a fortnight and then largely safe.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Slugs and snails
Checked 2026-08-13
Usually seen: March, April, May, June, September, October
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Plant out larger, hardened-off plants rather than small seedlings. Size is the most reliable protection there is: a module-raised plant with four true leaves survives what kills a direct-sown seedling.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Slugs and snails — cultural control
Checked 2026-08-13
- Water in the morning rather than the evening so the surface is drier at night, when they are active.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Slugs and snails
Checked 2026-08-13
- Clear damp hiding places next to vulnerable crops — loose boards, dense weed at bed edges, upturned pots.
source
Horticultural consensusmoderate confidence
- Garden Organic — Garden Organic (Henry Doubleday Research Association): Slug management
Checked 2026-08-13
Dealing with it once it is there
- Collect them after dark with a torch on mild damp evenings. Unglamorous, and more effective per hour spent than any barrier.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Slugs and snails — control
Checked 2026-08-13
- Biological control using the nematode Phasmarhabditis hermaphrodita, watered into moist warm soil. It works on slugs in the soil rather than snails on the surface, and it needs soil above about 5 °C.
Sourced guidanceDepends on conditionshigh confidence
Applies when: Effective against soil-dwelling slugs in warm moist soil; little use against snails, and it does not persist indefinitely.
- Royal Horticultural Society: Slugs — biological control
Checked 2026-08-13
Widely repeated, and not supported
Recorded so GrowingHQ can address them. These are not alternative approaches — they are things the evidence does not back.
“Crushed eggshells, coffee grounds, copper tape or sharp grit form a barrier slugs will not cross.”
Trials of the popular barrier materials have not found a measurable reduction in damage. Slugs cross all of them. The measures that do change outcomes are planting out at a larger size, evening collection, and nematodes in warm moist soil.
Horticultural consensusCommonly said, not supportedmoderate confidence
- Royal Horticultural Society: Slug barrier research
Checked 2026-08-13
What it affects
Signs that lead here
Each of these lists the other things that produce the same sign, and how to tell them apart.
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.
Plant-specific guides
Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.