Undaria pinnatifida

Asian seaweed, Japanese kelp, wakame

Family: Alariaceae · Type: Algae (Seaweed)

Conservation status: Cal-IPC Yes

Asian seaweed is a non-native marine algae found in coastal marine environments along the Pacific Coast of California. Reproducing through spores and vegetative fragments from March to November, this brown seaweed forms distinctive fronds with a broad, feather-like pinnate structure up to 2 meters long. Growing as an invasive species, it attaches to hard substrates like rocky coastlines, pier pilings, and boat hulls using a holdfast root-like structure. Its complex blade has a midrib with deeply cut pinnate segments that create a delicate, feather-like appearance. The seaweed can rapidly colonize marine habitats, forming dense underwater forests that can displace native marine species.

Bioregions: ChI

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Jepson eFlora, Cal-IPC, and more.