Lettuce: holes eaten in leaves

What it is likely to be on lettuce

1. Slugs and snails

   Candidate 1very common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Slugs and snails

   Checked 2026-08-13

   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.

   Points towards it

   • · a dried slime trail is conclusive and nothing else leaves one
   • · damage starts on the lowest leaves, nearest the ground the slugs come from
   • · an outdoor problem almost entirely

   Argues against it

   • · slugs are not an indoor problem in any normal circumstance — this rules it out entirely.

   Check this next

   Go out after dark with a torch and look at the underside of the leaves and the soil around the crown. Slugs feed at night, so an inspection at midday finds the damage and never the animal.

   What to do now

   Check at night and remove what you find, and clear the leaf litter and pot bases they shelter under during the day. On hostas, moving the plant into a container raised off the ground removes most of the pressure without any treatment at all.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Slugs and snails — control

   Checked 2026-08-13

2. Slugs and snails

   Candidate 2very common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Slugs and snails

   Checked 2026-08-13

   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.

   Points towards it

   • · both are soft-leaved and among the first things eaten in any garden
   • · the damage happens where the slugs can reach, which is not an indoor sill

   Argues against it

   • · an indoor plant is essentially never reached — this rules it out entirely.

   Check this next

   Move the plant indoors for a week and see whether new damage appears. These two are the clearest test in the catalogue because the answer is binary: outdoors they are eaten, indoors they are not, and no other cause of holes in a lettuce or a basil behaves that way. Look for the irregular ragged holes and the dried silver trail across the leaf in the morning.

   What to do now

   Grow basil in a pot on a hard surface or on a windowsill rather than in a bed, which removes the problem entirely. For lettuce, clear the hiding places within a metre of the row, water in the morning rather than the evening so the surface is dry at night, and go out with a torch after dark for a few nights — that finds more than any barrier.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Slugs and snails — cultural control

   Checked 2026-08-13

Narrow it down

This page lists everything at once, which is the right shape for reading and the wrong shape for deciding. The interactive tool asks one question at a time, starting with whichever would separate these causes fastest, and stops as soon as further answers would not help.

Opens with the plant and the symptom already set. Nothing you answer is stored or sent anywhere — the answers live in the address bar and nowhere else.

What this does not cover

These are the causes GrowingHQ holds rules for on lettuce — not every cause there is. Where several problems look alike, the honest answer is often that they cannot be told apart by eye, and a page that named one would be guessing. If none of the above fits, the general holes eaten in leaves page lists causes across all plants, and the Lettuce profile lists the problems it is prone to.