Description: Thallus terete and erect to about 50 cms long, main axis less than 2 mm wide. Densely branched, regularly opposite and distichous. In summer the fine, uniseriate, terminal filaments no more than 3 mm long, are lost.

Habitat: Fairly common. Epilithic in low littoral and sublittoral to 10 m.

Distribution: Widely distributed around the British Isles. Europe: Mediterranean, France, Netherlands, Denmark, Germany, Baltic, Sweden, Norway, Faroes and Iceland. Greenland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, Long Island and New Jersey. Further afield: Arctic Seas: Murman Sea, White Sea and the west coast of Greenland. Pacific coast of America: Alaska to California, Chile in South America, Japan and Antarctica.

Distribution Map from NBN: Desmarestia viridis at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Desmarestia viridis at iNaturalist World Species Observations database.

WoRMS: Desmarestia viridis at World Register of Marine Species. Accepted name: Desmarestia viridis (O.F.Müller) J.V.Lamouroux, 1813. AphiaID: 145310.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Desmarestiales; Desmarestiaceae; Desmarestia