Similar Species

Alaria fistulosa

Alaria fistulosa

This kelp is closely related to Undaria, but is native to the US West Coast. Like Undaria, both examples shown here are golden brown and have a midrib (central vein-like structure), but they have long skinny blades (leaves) rather than a broad blade with wing-like or finger-like projections on the edges. The blades also have a very smooth texture, unlike Undaria, which has a crinkly texture. Note also the additional leaf-like structures, which are actually reproductive structures, coming from the central stipe (stem) from the specimen on the sand. Undaria has only one blade per stipe and its reproductive structure looks like a pinecone.

Laminaria sp.


These kelp species are also native relatives of Undaria. Like Undaria, they have a conspicuous holdfast (root-like structure) by which they attach to docks, boats, rocks and other hard substrate. However, they have very long stipes (stems) relative to the length of their blades and they do not have a midrib.

Egregia sp.


This species is a similar color to Undaria and has a similar holdfast. As an adult it had a broad midrib, but it also has small paddle like blades and bulbs or floats on either side of the midrib. As a young plant, it has a crinkly texture and scalloped edges like Undaria, but no midrib. Undaria also does not have floats and is a single blade on a short stipe

Chondracanthus sp.


This species is common and can grow quite large. It sometimes has ruffled edges a bit like Undaria, but it does not have a midrib, and may have multiple blades arising from a single stipe. When healthy, it is a lovely reddish brown to maroon. Its very rough texture gives it the common name Turkish towel.

Macrocystis sp.


Macrocystis or giant kelp is common along the California coastline and sometimes can be found in harbors. It is a similar color to Undaria and has similar holdfasts, but it has very long stipes with multiple blades arising from them, and bulb-like hollow floats that help keep it buoyant underwater. Undaria does not have floats and is a single blade on a short stipe. Macrocystis also does not have a midrib.

Grateloupia sp.

Unsure grateloupia

This alga is common in harbors and can grow quite large. It is reddish-brown to maroon when healthy, but can look brown underwater. However, it does not have a midrib and often has multiple or split blades rather than a single large blade like Undaria.