This dark brown, perennial kelp grows from a creeping, branching rhizome which sends up thalli at intervals.

In 1972, the American phycologist James W. Markham did some transplanting experiments to try to determine whether the presence of mucilage glands is a distinctive feature or the two species were identical.

[3] Laminaria sinclairii is found in the northeastern Pacific Ocean, its range extending from Vancouver Island in British Columbia, southwards to Ventura County, California.

[2] This is the dominant seaweed on rocks in the lower part of the intertidal zone in Oregon on beaches where sand levels fluctuate dramatically at different times of year.

In March and April new thalli appear from the rhizomes but these blades are progressively buried by rising sand levels which results in the complete burial of the plants over the summer.