Why Is My Lettuce Full of Holes Overnight?

If your lettuce looks fine in the evening and shredded with ragged holes by morning, with shiny silvery trails across the leaves, you have the classic lettuce pest: slugs and snails. Lettuce is one of their absolute favourites, and they can destroy seedlings entirely and riddle mature leaves overnight. They are a persistent battle, but a combination of methods keeps them under control. Let me walk you through it.

Confirming it is slugs and snails

The signs are unmistakable once you know them: large, ragged holes chewed in the leaves, often from the edges, and on seedlings the whole plant may vanish; plus telltale silvery, glistening slime trails on the leaves, soil and pots in the morning. They feed at night and in damp, cool weather, and hide by day in cool, moist, dark places — under leaves, pots, boards and mulch. To confirm, go out an hour or two after dark with a torch and you will usually catch them in the act on the lettuce.

Hunting and trapping

Direct removal is highly effective. Hand-pick slugs and snails after dark by torchlight, or in the early morning, and drop them in soapy water — a few nightly hunts can dramatically reduce numbers. Set traps: a shallow dish of beer sunk to soil level draws and drowns them, and a board or upturned grapefruit half left out overnight gives them a daytime hiding spot you can lift and clear each morning. Trapping plus hand-picking, done consistently, is the backbone of slug control.

Barriers and deterrents

Make it hard for them to reach the lettuce. Ring plants or beds with a gritty barrier — crushed eggshell, sharp grit, or diatomaceous earth — that slugs dislike crossing. Copper tape around containers and beds gives them a tiny shock and deters them effectively. Remove their daytime hiding places by keeping the area around the lettuce clear of debris, boards and dense mulch right against the plants. Watering in the morning rather than the evening leaves the surface drier at night when they feed.

Encourage predators and protect seedlings

Nature helps: birds, frogs, toads, ground beetles and hedgehogs all eat slugs and snails, so a garden friendly to wildlife keeps numbers down. Avoid harming these allies with broad poisons; if you use slug pellets, choose the wildlife-safe iron-phosphate type. Protect vulnerable seedlings above all — they are the most likely to be wiped out — using cloches, collars, or by raising plants to a sturdier size before planting out. With a layered approach of hunting, trapping, barriers and predators, you can keep slugs and snails from shredding your lettuce.