Gutweed ©Dorset Wildlife Trust


Scientific name: Ulva intestinalis
This grass-green seaweed is sometimes known as Grass Kelp and grows on pretty much every shore in the UK.

Species information


Length: up to 40cm Frond width: 6-18mm

Conservation status


When to see

January to December


Gutweed is a common seaweed found on all UK shores and in many different habitats, including rock pools, sand, mud and even shells and other seaweeds! It is often seen with bubbles of air trapped inside its long fronds which have the look of intestines, hence its name. If detached, Gutweed can create large floating masses, buoyed by the gas in their inflated tubular fronds. Dense growths of Gutweed provide shelter for many other creatures, with their moist fronds providing a low tide refuge on the high shore.

How to identify

Gutweed is a mass of bright green, inflated tubes, often with pinched-in 'waists' along its length. Fronds are typically unbranched.


Found on all UK coasts.

Did you know?

This fast-growing species reproduces quickly and can turn water green with the release of masses of gametes and spores.

How people can help

Seaweeds provide a vital link in the food chain for many of our rarer species. The Wildlife Trusts are working with fishermen, researchers, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives. Do your bit for our Living Seas by supporting your local Wildlife Trust or checking out our Action pages.