So I'm quite into foraging, and seaweed (the real thing not chinese take away stuff...) is supposedly very nutritious for you and very easy to forage up, but are there any seaweeds which are not edible, or possibly not worth eating, on UK shorelines?

2 Answers 2


There is one poisonous: the Desmarestia. The other species should be okay. However, I can't say anything about if they are "worth eating" :)

Desmarestia is a genus of brown algae found worldwide. Members of this genus can be either annual or perennial. Annual members of this genus can produce and store sulfuric acid in intracellular vacuoles. When exposed to air they release the acid, thereby destroying themselves and nearby seaweeds in the process. They are found in shallow intertidal areas.

Avoid this


So I went and asked Professor Michael Guiry, Director of AlgaeBase and world authority on seaweed. Here’s his reply:

“As far as I know, there are no really poisonous seaweed in this part of the world. “Our” Desmarestia species (4 of them and as you said mostly in deep water) produce sulphuric acid and can have a cellular pH of 2.

Anything else you might want to eat is free of poisons in the conventional sense as far as I am aware. However, care should be exercised when collecting in areas with high coliform counts and other bacteria, particularly in estuaries.


Further reading: blog post by Ginger Hultin

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    Regarding the deleted paragraph - I wonder what they've got against that part of the coast... I live in Felixstowe, and (up until a couple of years ago, not had it renewed for what seems like administrative/political reasons) we regularly had a Blue Flag award despite being host to the UK's biggest container port... Commented Dec 2, 2015 at 11:30

Here in the UK, there are several varieties of seaweeds that are tasty and are readily available for foraging, each with its unique flavour and texture.

While they are strictly no poisonous/unsafe seaweeds found in UK waters, there are some you’ll probably want to stay clear off due to their unpalatable taste or texture.

Examples of seaweeds to avoid include:

Mermaid's hair (Desmarestia viridis) – this one is high in sulphuric acid which it releases as a defence mechanism to discourage grazing fish from eating it.

Bladderwrack (Fucus vesiculosus) - This brown algae can be found on rocky shores and in shallow waters. It has a high iodine content.

Dead man's fingers (Codium fragile) - This green algae can be found in rock pools and shallow waters, but it is not considered edible due to its unpalatable taste.

Edible UK seaweed examples include:

Wakame which is frequently used in soups and stews and has a slightly salty taste.

Dulse is a popular seaweed that has a smoky flavour.

Kombu is also a commonly eaten seaweed and it has a slightly sweet and salty flavour and is often used as a flavour enhancer in soups, stews, and broths.

Sea lettuce is easy to forage for. It is a leafy green seaweed that has a mild and slightly salty flavour. It’s perfect for use in salads or as a garnish.

If you're interested in using seaweed as a thickening agent, Irish moss is an excellent option. It has a neutral flavour and can be used in custards, puddings, etc.

You can find out more about foraging for seaweeds in this coastal foraging guide which I found useful: Coastal Foraging Guide

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