Phycodrys rubens is seaweed which is perennial and can grow to 30 cm long and is strongly red in colour.

[2][3] The algae are somewhat similar to Delesseria sanguinea which is also strongly red but has a smooth, not dentate, margin.

[2] The reproductive structures are found at the margins of the blades, the cystocarps as branches attached to the veins[4] and the tetrasporangial sori occur near the apices of the larger bladelets.

[2] Commonly found in the littoral, sub-littoral in low rock pools and attached to the stipes of large algae such a Laminaria.

Found to a depth 30 m.[2] Common on the shores of Ireland, Wales, Isle of Man, Scotland including the Shetland Islands and the north-east and south-east of England.