How to identify seaweed

Seaweeds require enough light to photosynthesise, so are most abundant in the intertidal zone – especially along rocky shores. Here are 12 for you to spot. 

Purple laver, Porphyra umbilicalis

                                                                           Illustrations by Dan Cole/The Art Agency 


1 Purple laver Porphyra umbilicalis (above

Small and purple, with broad, tough fronds. Found in upper zone of rocky shores. Edible; eaten as laver bread.



2 Oarweed Laminaria digitata

A glossy, golden-brown kelp up to 2m long, with distinctive ‘fingers’ on broad fronds. Exposed at low tide.



3 Furbelows Saccorhiza polyschides

A brown kelp with a frilled stem and large bulbous holdfast that attaches to rocks. Revealed at low spring tides.



4 Bladderwrack Fucus vesiculosus

Olive-brown and up to 2m long, with air bladders at the frond ends. Forms beds in mid-zone of rocky shores.



5 Channelled wrack Pelvetia canaliculata

Brown and up to 15cm long, with fronds that curve inwards to create a channel. Found at top of the shore. 



6 Pepper dulse Osmundea pinnatifida

Small, red or brown, fern-shaped seaweed of sheltered rocky coves. Edible; used as a curry-like spice.



7 Coral weed Corallina officinalis

Small, pink or purple seaweed with a feathery structure. Forms a dense carpet in pools on rocky shores.



8 Carrageen Chondrus crispus

Purple, with flat fronds up to 20cm long. Found on rocks on lower shore. Edible; used as a thickening agent.



9 Sugar kelp Saccharina latissima 

A brown kelp up to 2m long, with frilly fronds. Found below low-tide mark. Edible; used as a sugar substitute.



10 Gut weed Enteromorpha intestinalis

Green, grass-like seaweed with tubular fronds. Found on rocks, sand or mud at all levels of the shore.



11 Velvet horn Codium tomentosum

Green seaweed with spongy texture resembling deer antler ‘velvet’. Found in rockpools and on lower shore.



12 Sea lettuce Ulva lactuca

Small and green, with crumpled, lettuce-like fronds. Grows on rocks in mid-zone of shores. Edible.


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