Young Versus Mature Undaria Comparison
With a little bit of practice, it is easy to distinguish Undaria from other kelp species in North America.
Look for the following characteristics:
- A golden brown color. Color can be hard to judge underwater. Bring the suspected algae to the surface to check color. If your specimen is green, red, maroon or brownish red, it is not Undaria.
- No floats or gas bladders. Many native algae, such as the giant kelp Macrocystis have air-filled floats that help them float up near the surface of the water.
- A single stipe (stem) and blade (leaf). Many native algae are branching, with multiple stipes and blades. The blade will have fingerlike projections around the edges in a mature plant. Younger plants are flame-shaped.
- A midrib (similar to a central vein in a leaf) that runs most of the length of blade. This can be quite thick in large, mature individual. Younger plants will have a partial midrib.
- A coiled, scalloped reproductive structure below the blade will be present on mature plants. Some people describe this as looking like a large open pinecone.
- A crumpled, crinkly texture. Some closely related native kelp species are similar in color and have a midrib, but are quite smooth.