The best time to deal with slugs is now, not next May
Slugs lay their eggs in autumn. Find the clutches now and you'll have far fewer slugs on your seedlings next spring – and far less work.
It’s the same picture every year: your young lettuce plants are standing there in May, and overnight they’re gone. Then comes the nightly hand-picking, the beer traps, the swearing. But the slug year isn’t decided in May – it’s decided right now, in September and October.
Why autumn decides your spring
Slugs – the Spanish slug in particular – lay their eggs mainly between late August and October. A single animal lays several clutches of roughly twenty to forty eggs each. Some of them hatch in autumn and the young slugs then overwinter in the soil; the rest stay as eggs and hatch as soon as spring turns mild and damp.
Which means: every clutch you find now is dozens of slugs fewer working their way through your lettuce in May. And unlike night-time hand-picking, this works in daylight, in the dry, without a torch.
What the clutches look like – and where they hide
Slug eggs are round to slightly oval, three to four millimetres across, milky white to pearly, and always sit clustered together. Single scattered spheres are usually something else.
Look where it’s damp, dark and sheltered: under boards and paving slabs, under upturned pots, in the mulch layer, in soil cracks and cavities, around the edge of the compost heap, under dense ground cover – and very often along the outer edge of a raised bed.
What to do with a find: lift the clutch out carefully and spread it on a dry, sunny surface, where the eggs will dry out. Don’t put it on the compost heap – that is exactly as warm and damp as the eggs need it to be.
One note that matters more than it sounds: not every slug in your garden is a problem. The leopard slug – grey with dark markings – actually eats the eggs of pest slugs and is a genuine ally. The Roman snail is a specially protected species in Germany, protected in Switzerland, and protected in most Austrian federal states. Its clutches tend to be a little larger and more translucent, but you can’t tell them apart reliably by eye. So when in doubt: leave the find alone and work with traps instead.
The board trap: unspectacular, but it works
Lay a few untreated wooden boards or old bricks flat on the soil, spread across your beds. Underneath, it gets exactly as damp and dark as slugs like it for laying eggs. Every two or three days you flip them over and collect whatever you find.
The nice part: the check takes five minutes, works in daylight, and delegates beautifully. Kids tend to find this kind of treasure hunt considerably more exciting than pulling weeds.
Mulch: a friend in summer, a nursery in autumn
A mulch layer keeps moisture in the soil over summer and protects soil life – that still holds true. But in beds that suffered badly from slugs this past spring, it’s worth keeping the mulch thinner in autumn, or moving it aside for a while.
Lightly hoeing through the top two or three centimetres in exactly those problem beds exposes any clutches: they dry out, or get found by birds and ground beetles. You don’t need to dig deep for this – quite the opposite, that would do more harm to the soil structure than to the slugs.
Invite the beneficials to overwinter
The most effective slug defence works all year round and costs nothing: hedgehogs, shrews, toads, ground beetles, slow worms and birds all eat slugs and their eggs. And right now, in autumn, they all need the same thing – somewhere to spend the winter.
A pile of leaves in a quiet corner, a stack of deadwood, a few stones layered up on the north side: that’s fifteen minutes of work and the best investment you can make in your spring. One condition: these piles stay put well into April. Tidy up in March and you evict your lodgers before they can start work.
Write down where you find them
Slugs are creatures of habit. The damp corner behind the raised bed, the strip beside the compost – year after year, it tends to be the same spots. If you note down where you found clutches this autumn, you’ll know exactly where not to put your vulnerable young plants next spring.
In Rootivo you can record observations like these in the garden journal – with a date, a photo and the bed they belong to. Come February, when you’re planning your beds again, you’ll have your own notes instead of vague memories.