Water lettuce Pistia stratiotes

Status Non-native, invasive
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An invasive, non-native plant.

As the name implies, this species looks like a small lettuce. It floats on the surface of the water and is very popular for ponds and pools, being widely available from garden centres and aquatic centres.

What's the problem?

In warmer climates, it is a serious problem on lakes, ponds, canals and slow moving rivers, where it carpets the water surface, excluding light and depleting oxygen levels. It has been recorded from similar places in the wild in Britain but only as a casual – it doesn’t survive or spread in our current climate. Should the climate continue to warm though it has the potential to do so in mild areas in the future.

Rapid Risk Assessment

*** Moderate Risk