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Woodlouse, who would’ve guessed roly-polys were so useful?

Woodlouse, a useful garden animal

The woodlouse is not a garden helper in the “classic” sense: it doesn’t hunt pests, nor does it help in pollination.However, as a detrivore, it is one of the keys to successful gardening. Indeed, it helps feed the soil and plants by breaking down all plant waste (rotting wood, dead leaves, etc.).

Discover this unexpected ally of the gardener.

Woodlouse: an identification guide

Contrary to what one might think, the woodlouse is not an insect. Indeed, it belongs to the class of Crustaceans and the order of isopods. In short, it’s a relative of crabs and lobsters!


Description and identification of a woodlouseA woodlouse is easy to recognize:

  • it has a characteristic flat and oval shape;
  • 7 pairs of legs and 2 large antennae;
  • 2 appendages at the end of the abdomen that allow it to breathe;
  • a color that is more or less pronounced gray;
  • a size ranging from 0.2 inches (5 mm) to 0.8 inches (2 cm).

The species that you often find in the garden include:

  • Common rough woodlouse (Porcellio scaber), measuring up to 0.7 inches (1.7 cm) and steel gray in color. It is the one most commonly found in houses.
  • Wall woodlouse (Oniscus murarius), distinguishable by its lighter gray color, almost white.
  • Moss woodlouse (Philoscia muscorum), with a gray-brown color and reaching up to 0.4 inches (1 cm) long.
  • And finally, the common pill bug (Armadillidium vulgare), measuring about 0.8 inches (2 cm), gray in color, with the unique ability to roll into a ball when threatened. Many of us played with roly-polies when we were kids!


Lifecycle of a woodlouseThe woodlouse is a land crustacean. Its ancestors came from the sea, and till today these animals still breathe through gills and have a a non-waterproof shell. These features make it vulnerable to drying out, so it can only survive in a humid, moist atmosphere. That’s why it comes out mainly at night and on rainy days.

As a recycler and detrivore, the woodlouse feeds on dead organic matter: rotting bark, dead leaves, or even corpses of insects or animals. It can supplement this diet with mushrooms, roots, or young shoots. However, this vegetarian part of its diet is not enough to cause damage to crops.

Did you know?

Like lichen on trees indicating a non-polluted atmosphere, and voles, the woodlouse is an excellent indicator of healthy soil. Indeed, it is particularly sensitive to heavy metals (lead, zinc, copper, etc.) and disappears if these are present in excess.

Woodlouse Habitat:

Woodlouse habitatIn the garden, you will find the woodlouse wherever it is humid enough for it:

  • under bark or stones;
  • in a carpet of moss;
  • hidden in rotting plant matter on the ground.

You may encounter a woodlouse in your house (basement, kitchen, garage, etc.). If there’s only one, it is not a problem. However, if there are more, it could mean there is a water leak or infiltration somewhere. You would then need to investigate.

Woodlouse utility for gardeners

Just like the earthworm, the woodlouse is vital for the health of your soil in the vegetable garden and yard. By decomposing dead organic matter, it makes nutrients available again for plants. It thus contributes to the soil’s proper ecological balance. Therefore, it’s important to protect it.

How to Attract and Protect the Woodlouse in Your Garden?

Attract and protect woodliceFor this, nothing could be simpler. Just provide the woodlouse with shelter, especially near areas where it will be most useful. For instance, you can:

  • lay a few logs or dead branches in a pile near the compost pile or vegetable garden;
  • place flat stones, tiles, or planks along the edge of a flower bed (use them for edging, perhaps);
  • etc.

Finally, even though it might seem absurd, resist the urge to always remove moss from the lawn. It indeed forms an ideal biotope for the woodlouse. If possible, maintain a part of the garden with some patches of moss, it will make woodlice happy.

To summarize, far from being a pest, the woodlouse plays a crucial role for the health of your soil by recycling dead organic matter. All you have to do now is to set up a few well-placed shelters to make its life easier in your garden.

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Written by Christophe Dutertre | With a formal degree in landscaping and an informal love of gardens, Christophe will introduce you to this passion we all share. Novelty, down-to-earth tips and environment-friendly techniques are marked on the map, so let's get going!
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