It contains around 40 species and has a cosmopolitan distribution in temperate seas, although it is most diverse in the southern hemisphere.

[4] Plocamium has erect elliptical thalli that grow up to 50 cm (20 in) in length.

They are bright red in color with strongly flattened delicately branching fronds that further divide into two to five smaller branchlets.

[5][6] Cystocarps (fruiting parts) are either scattered along the frond margins or found on special short fertile branches, and lack a specialized pore for carpospore release.

Tetrasporangia are borne in specialized stichidia (branches of the thallus) of various morphologies.