Ulva intestinalis


Gutweed is a common seaweed of rock pools, saltmarshes and seawater ditches, and is particularly abundant in brackish water. It is often seen with bubbles of air trapped inside its long fronds which have the look of intestines, hence its name. It is sometimes attached to substrate, but may become detached, forming floating, growing masses. It is a summer annual so will decay and form masses of bleached fronds towards the end of the season.

How to identify

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

Where to find it

All around our coasts.


When to find it

  • January
  • February
  • March
  • April
  • May
  • June
  • July
  • August
  • September
  • October
  • November
  • December

How can people help

Seaweeds provide a vital link in the food chain for many of our rarer species. Our seas and coastline are in need of protection if we are to keep our marine wildlife healthy. The Wildlife Trusts are working with fishermen, researchers, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives. This work has recently had a massive boost with the passing of the Marine Bill, promising sustainable development of the UK's marine environment. Do your bit for our Living Seas by supporting your local Wildlife Trust.

Species information

Common name
Latin name
Ulva intestinalis
Seaweeds and grasses
Length: up to 75cm Frond width: 6-18mm
Conservation status