Postelsia

Sea palm
Postelsia palmaeformis growing in its native habitat at low tide
Scientific classification
Domain: Eukaryota
Clade: Sar
Clade: Stramenopiles
Division: Ochrophyta
Class: Phaeophyceae
Order: Laminariales
Family: Laminariaceae
Genus: Postelsia
Ruprecht, 1852
Species:
P. palmaeformis
Binomial name
Postelsia palmaeformis
Ruprecht, 1852

Postelsia palmaeformis, also known as the sea palm (not to be confused with the southern sea palm) or palm seaweed, is a species of kelp and classified within brown algae in the SAR supergroup of eukaryotes. It is the only known species in the genus Postelsia. The sea palm is found along the western coast of North America, on rocky shores with constant waves.

It is one of very few multicellular organisms with differentiated tissues that spends most of its life out of water and is neither animal, fungus, plant, nor closely related to either of those. It is edible, though harvesting of the alga is discouraged due to the species' sensitivity to overharvesting.