Key takeaways
- Woodlice mostly eat dead plant material and rarely attack healthy plants
- Damage happens mainly to soft seedlings in damp, cluttered greenhouses
- They often get blamed for holes in strawberries that slugs started
- Clear boards, old pots and debris where woodlice hide by day
- Good ventilation and morning watering make a greenhouse less inviting
- In the open garden and compost heap, leave them be: they're helpful recyclers
Woodlice rarely harm healthy plants. They mostly eat dead leaves, rotting wood and other debris, which makes them useful recyclers in the garden. The two places they can cause trouble are damp, cluttered greenhouses, where they nibble soft seedlings, and strawberry beds, where they move into fruit that slugs have already damaged.
So the answer is rarely to “get rid of” woodlice everywhere. It’s to make the greenhouse and seedling areas less comfortable for them. This guide shows you how to tell whether woodlice are really the culprit, and what to do if they are.
What do woodlice eat?
Woodlice are small land-living crustaceans, related to crabs and shrimps rather than insects. They need damp conditions and hide by day under stones, wood and pots.
Their main food is dead and decaying plant material: fallen leaves, rotting wood, old stems and the odd fungus. That’s why you’ll find so many in compost heaps and under log piles. They help turn garden waste into crumbly compost. Birds, shrews, toads, frogs and spiders eat them in turn.
They can’t tunnel into firm, healthy stems. Damage to living plants happens when food and shelter are plentiful right next to something soft, such as a tray of seedlings on a damp greenhouse floor.
If you’re not sure what you’re looking at, woodlice have seven pairs of legs and an oval, armoured grey body. Millipedes are long and thin with many more legs. The centipede and millipede guide helps tell them apart.
When do woodlice actually cause damage?
Most gardens never need to do anything about woodlice. They’re worth tackling in three situations.
Seedlings in a damp greenhouse. Where woodlice are numerous, they can nibble the soft stems and leaves of young seedlings at night, especially cucumbers, courgettes and beans. Check after dark with a torch to see who’s really feeding.
Ripe strawberries on the soil. You’ll often find woodlice inside hollowed-out strawberries. Usually slugs or birds made the first hole, and the woodlice moved in afterwards. The guide to getting rid of slugs covers the real culprit.
Indoors. Woodlice in the house are a sign of damp, such as a leak or condensation. Fix the damp and they’ll disappear.
Seedlings that collapse at soil level may have something else wrong. Damping off, a fungal disease, makes young stems go thin and dark at the base. The damping off guide shows the signs. Cutworms, fat caterpillars in the soil, sever stems too: see the cutworm guide.
In a damp greenhouse, woodlice can nibble soft seedlings. Check with a torch after dark to be sure they’re the ones feeding.
How to get rid of woodlice in a greenhouse
The best way to cut woodlouse numbers is to remove their daytime hiding places. No hiding spots, no crowds of woodlice.
- Clear the floor. Lift wooden boards, bricks and old sacks lying on the ground or on damp soil.
- Tidy under the staging. Stacks of empty pots and trays make perfect shelters. Store them dry, off the floor.
- Sweep up debris. Pick up fallen leaves, dead flowers and old compost regularly.
- Raise seed trays. Put trays on staging or a bench rather than straight on the floor.
- Give a thorough clean. A good clear-out in autumn or late winter leaves fewer places to shelter.
You can also use a simple trap. Lay an upturned flowerpot stuffed with damp straw, or half a scooped-out potato cut-side down, near the seedlings. Lift it each morning and move the woodlice to the compost heap.
Lift any boards lying on a damp greenhouse floor and you’ll see where the woodlice live. Take the boards away and the crowd moves on.
Clutter on the floor gives woodlice endless hiding places. A cleared floor with pots stored on shelves leaves them nowhere to go.
Ventilate to dry the greenhouse out
Woodlice need damp air and lose water quickly in dry conditions. A well-ventilated greenhouse is less inviting to them, and better for most plants too.
- Open roof vents and the door on dry, mild days.
- Water in the morning so surfaces dry out before night.
- Water at the base rather than soaking the floor and staging.
- Space plants out so air can move round them.
- Add an extra vent if your greenhouse only has one roof vent and stays humid.
The guide to greenhouse ventilation and humidity control covers vents and automatic openers in more detail.
Open roof vents and a low louvre vent keep air moving. A drier greenhouse suits your plants better than it suits woodlice.
Protecting strawberries and outdoor seedlings
Outdoors, focus on the crops that matter and leave woodlice alone everywhere else.
Straw under the fruit keeps berries off damp soil, so slugs and woodlice are less likely to get there first.
Strawberries: Tuck straw or strawberry mats under the fruit as it forms, so berries don’t sit on damp soil. Pick fruit as soon as it ripens and clear away any damaged ones. Deal with slugs, which usually start the damage. The guide to growing strawberries covers strawing up and picking.
Seedlings: Grow young plants on a little until their stems are firmer before planting out. Keep mulch and debris pulled back from tiny seedlings for the first few weeks.
Leave them in: the compost heap, leaf litter under shrubs and log piles. They’re doing a useful job there.
Should you use sprays or powders?
You don’t need any. Woodlice are easy to discourage by tidying their hiding places. Sprays would also harm the ground beetles, spiders and other helpful creatures living alongside them.
Home-made sprays aren’t legal to use as pesticides in the UK, and they can damage plants. If you ever do want a product, use one approved for that use and follow the label.
Woodlice through the year
| Month | What to do |
|---|---|
| January to February | Clear the greenhouse floor and under the staging |
| March to April | Raise seed trays off the floor. Ventilate on mild days |
| May | Check seedlings by torchlight if you see damage |
| June | Straw up strawberries. Pick ripe fruit promptly |
| July to August | Ventilate well in hot spells. Water in the morning |
| September to October | Sweep out leaves and plant debris |
| November to December | Store empty pots dry and off the floor |
Common woodlice mistakes
Blaming woodlice for slug damage. Woodlice often move into holes slugs made. Check at night to see who’s really feeding.
Treating the whole garden. Woodlice in compost, leaf litter and borders are helpful. Only tackle them near seedlings.
Leaving boards and pots on the greenhouse floor. That’s where the crowds live. Clear them away.
Watering in the evening. A greenhouse that stays damp overnight suits woodlice. Water in the morning instead.
Frequently asked questions
Do woodlice damage garden plants?
Rarely, as they mostly eat dead and rotting plant material. In damp greenhouses they can nibble soft seedlings. Outdoors they may feed on strawberries or other soft fruit, usually where slugs have already broken the skin.
How do I get rid of woodlice in a greenhouse?
Remove the damp places they hide by day. Clear old boards, stacks of pots and plant debris from the floor and under the staging. Open vents on dry days and water in the morning so the greenhouse dries out by night.
Are woodlice good or bad for the garden?
Mostly good. They break down dead leaves and rotting wood, which helps make compost and feeds the soil. They’re also food for birds, shrews, toads and spiders. Only tackle them where they’re damaging seedlings.
Should I spray woodlice?
No, sprays aren’t needed. Woodlice are easy to discourage by clearing their damp hiding places. Spraying would also harm the beetles, spiders and other helpful creatures that share their habitat.
Why do I have so many woodlice in my greenhouse?
They love damp, dark hiding places and rotting debris. Wooden boards on the floor, old pots, fallen leaves and wet corners all suit them. Tidy the floor and improve the airflow, and numbers soon drop.
Why are there woodlice in my house?
Usually because somewhere is damp. Woodlice dry out quickly indoors and don’t breed there for long. Look for leaks, condensation or damp walls near where you see them, and fix that.
Now you know woodlice are mostly friends, read our guide to composting for wildlife to put them to work, or browse more garden problem guides.
Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
