What's the difference between bull kelp and giant kelp?

November 2018

Along the West Coast, lush jungles of giant kelp and bull kelp create habitat for everything from sea lions to juvenile fish. Do you know the differences between the two kelp species?


Kelp forests provide habitat, protection, and food for a wide variety of animals and plants.

Bull kelp is the most abundant kelp in Oregon, Washington, British Columbia, and Alaska.

Its cousin, giant kelp, dominates to the south.

Bull kelp has long, narrow blades growing from a bulbous float. Its blades form a golden brown canopy on the water's surface.

Unlike bull kelp, giant kelp has blades growing all along its stem

Giant kelp often grows in turbulent water, which brings renewed supplies of nutrients, allowing some to grow to a height of 175 feet.

Bull kelp can grow up two two inches a day, while giant kelp can add a foot or more of new foliage each day.

In recent years, changing ocean conditions have led to a die-off of bull kelp in Northern California.

The causes and potential solutions of the die-off are being investigated, but recovery has yet to begin, and ecosystem disruptions persist.

Both these kelp species act as backbones for lush ecosystems, helping species thrive in your national marine sanctuaries.