The Overnight Guest List: What Your Slug Trap Is Really Catching After Dark

By November 2026, most UK borders are less 'planted' and more 'damply occupied'. Slugs are still on the move in mild, wet spells, and the usual traps come out of the shed: a sunken beer trap, a grapefruit half, a bit of damp sacking. They all catch something. The question is whether they catch the right things, and whether the faff is worth it.

This is not a war manual. It is an honest audit. Traps are useful as monitoring tools and small-scale intercepts, not as a set-and-forget solution. Set them badly and they become killing jars for ground beetles, flies and the occasional newt. Set them well, check them daily, and they can tell you where the pressure is without turning your border into a miniature abattoir.

Sunken beer traps: the classic that fills up fast

A sunken beer trap is the gateway drug of slug control. You bury a pot, leave the rim a couple of centimetres above soil level, half-fill it with beer and wait. In wet autumn weather it will catch slugs. It will also catch a lot of other things, and the beer goes stale or gets diluted by rain surprisingly quickly.

If you use one, give it a lid or a propped-up slate cover so rain does not flood it and hedgehogs cannot get their snouts in. Keep the liquid shallow, check every morning, and empty it somewhere the contents will not poison anything. A trap left for three days is not a trap; it is a soup.

Cost is low, effort is moderate, bycatch is the problem. Beer traps are best used briefly, in one or two known hotspots, as a census rather than a cure.

Citrus halves and melon shells: shelter, not a magnet

There is a stubborn idea that slugs cannot resist an upturned grapefruit half. In reality, citrus is mostly a cool, damp hide. Slugs use it because it is there, not because it smells like a pub. That matters: a citrus half under a shrub is a monitoring station, not a vacuum cleaner.

Check it each morning, lift it gently, and deal with whatever is underneath. Do not leave it for a week to turn into a mouldy fruit fly nursery. If you are relocating slugs, take them well away from the border and into a hedge, copse or compost heap where they can be something else's dinner. If you are not, bin them. Either way, be consistent.

Damp sacking, cardboard and the morning shake-out

This is the low-cost, low-tech option that actually earns its place. A folded piece of damp sacking, a flattened cardboard box or a couple of old roof tiles laid on bare soil will pull slugs in as a daytime refuge. In the morning, lift, shake into a bucket, and relocate or dispose. It is quick, it costs nothing, and you can see what you have caught.

Cardboard has a caveat: it is also brilliant habitat for ground beetles and other invertebrates you want to keep. Check before you squash. And do not leave sodden cardboard down for weeks on end; it becomes a slug nursery and a mess. Use it for a few days, then compost it.

Proprietary slug hotels: read the small print

Slug hotels look tidy and promise a permanent solution. Some are well designed; many are simply damp plastic shelters with a lid. They cost £10–£25, need emptying regularly, and can become a breeding site if ignored. The honest verdict: they are a convenient hide, not a force field. If you buy one, treat it like a sacking trap with a price tag. Check daily, empty into a bucket, and do not assume the slugs have gone anywhere.

The bycatch problem: hedgehogs, newts and beetles

This is where kindness and good gardening overlap. A sunken pit of beer is a hazard for hedgehogs, frogs and newts, and it drowns the ground beetles that eat slug eggs. Ground beetles are your allies. Newts are protected and should not be turning up dead in your borders. Hedgehogs are already having a hard enough time.

So: no open drowning pits, no traps left unchecked, no beer traps near ponds or hedgehog runs. Use covers, raise rims, and check first thing. If you find a beetle, let it go. If you find a newt, rethink the trap.

The torch patrol: the benchmark

Here is the uncomfortable truth. A ten-minute evening walk with a torch after rain, a bucket and a pair of gloves will out-perform most traps for immediate reduction. You see where the slugs are, you take only what you can see, and you avoid bycatch almost entirely. It is not glamorous, but it is precise.

Traps still have a role: they tell you which parts of the garden are under pressure when you cannot get out at night. Use them as an audit, not a crutch.

A sensible wet-weather routine

Set one or two damp sacking traps in known hotspots. Check them each morning for a week. Keep a rough count, then remove them. If you use a beer trap, cover it, shallow-fill it, and empty it daily for no more than a few days. Leave citrus halves out of the equation unless you genuinely enjoy the routine. And if you are going to spend money, spend it on a decent torch and a bucket.

No Slug's view is simple: traps are for learning, not for winning. Use them lightly, check them often, and let the hedgehogs and beetles off the hook.