Flatworms in the garden: can they harm vegetable gardens?

In the garden and vegetable patch, you're always discovering new things. New flowers, pollinators we knew little or nothing about... Nature is full of beautiful things and we never stop wanting to bring colour from elsewhere into our gardens. However, this craze is not without consequences, since importing foreign plants also unwittingly brings with it pests from faraway lands. In particular, we have imported Asian hornets, which are now veritable predators of our bees and pollinators in general. The same goes for flatworms. Less well known, they are nonetheless a threat to our gardens.

Focus on the flatworm

Little known to gardeners at the moment, there are two species. The first called Obama nungara is native to South America and is easily recognised by its flat appearance. It can measure from 5 to 10 centimetres. It can be brown or black in colour. This worm moves slowly, usually at night. It is the most common flatworm in France. Studies have shown that it does not develop in mountainous regions. It was reported in 2013 and since then research into this species has been ongoing.

A second species, from the order Plathelminthes, also known as the New Guinea flatworm is present in western France and was discovered in 2014 in the hot greenhouses of the city of Caen. It is brown in colour with a characteristic yellow line on the top of its body. It can measure up to 5 centimetres. Like its predecessor, studies are under way to find out more about these species.

The flatworm and biodiversity

The problem with introducing exotic species is that they can very quickly become invasive. Having no predators in Europe, they can develop and proliferate without fear of any threat. On the other hand, they are a real threat to our biodiversity. Flatworms feed on snails, slugs and earthworms. Very bad news for our earthworms, which are so important in our gardens.

The earthworm is one of the most useful invertebrates in the garden. When it moves, it digs galleries that keep the soil well aerated. They break down all the organic matter in your garden, from compost to branches and leaves. It transforms all this into nutrients that allow us to enjoy enriched soil. The richer your soil is in earthworms, the healthier it will be...It would be unthinkable to see them disappear from our land.

What should I do if I find flatworms in my garden?

There is currently no natural or chemical way of getting rid of this new invader. You can, however, take a photo of it and give a short description (size, colour, where you found it). You can then report it to the relevant authority. It's our responsibility to buy responsibly to avoid introducing invasive species. So don't hesitate to ask before ordering exotic plants.