A frilly crimson ruffle

Found on the beach: a frilly crimson tuft washed ashore, striking against the pebbles like a splash of paint. This is Chondrus crispus, better known as Irish moss or carrageen, one of the most distinctive of the red seaweeds. Its fronds are flat and forked, often 2-15 cm long, with tips that curl into a lacework of ruffles. The colour varies from greenish through deep red to purple, depending on age, light and water conditions. 

Like many algae, Chondrus has a complex life cycle that alternates between two diploid generations and a haploid gametophyte phase. Fertilised female fronds develop tiny cystocarps where spores form, and these are carried back into the sea to grow into new plants. This alternation of generations, shared across the red algae, means the seaweed thrives in different conditions and ensures its persistence around the rocky Atlantic coasts of Europe and North America.

Though small, Chondrus crispus has long had a large presence in coastal life. In Ireland it was gathered and boiled in milk to make a sweet blancmange, while in the 19th century it was sold as a remedy for coughs and chest ailments. Its processed extract - carrageenan - is now a global commodity, valued for its ability to gel and thicken. 

Food scientists prize the seaweed’s stabilising properties, and it turns up in ice cream, custard, yoghurt, beer, toothpaste and even some cosmetics. Dried and rehydrated, it can still be cooked into traditional puddings or soups; eaten raw, it carries the taste of the tide. Foragers warn that it should only be taken from clean waters and not picked from beach wrack,

Traditionally, Irish moss is hand-raked or gathered by hand at low tide from rocky intertidal zones. In some places, small boats were used to drag rakes or nets over the seaweed beds. Harvesting is usually concentrated in late spring and summer when growth is fastest. Collectors often follow local licensing or community rules to avoid damaging the beds. Once gathered, the seaweed is washed in seawater to remove sand and shells, then spread out on beaches or fields to dry in the sun. This drying both preserves the seaweed and enhances the gel strength of carrageenan.

For further information see the Marine Life Information Network, the UN Food and Agriculture Organization and Totally Wild UK (our main goal is to excite people with the amazing flavours to be found in the wild).