Southern kelp, also known as sugar kelp, is a large brown algae species that can grow to lengths over six feet. The kelp consists of three parts:
- Blade: the wide, flat, leaf-like structure.
- Stipe: the stem-like structure that runs from the blade to the holdfast.
- Holdfast: the root-like structure that attaches the kelp to a hard substrate like a piling, rock or mussel shell.
Southern kelp is usually a dark brown color with a rippled appearance and edges resembling a lasagna noodle. It also has bullations (depressions) along the length of its blade on each side. When southern kelp dries, a sugary white deposit forms on the kelp's surface, which is how it got the species name saccharina and one of its common names, sugar kelp.
Southern kelp is also known as the "poor man's weather glass," as it is said that if you hang a frond of southern kelp in your home, it becomes soft and limp if rain is coming, and stiff if dry weather is coming.
Southern kelp is a cold-water species common off the Pacific coast of the U.S. from Alaska to California, and off the eastern U.S. coast from Maine to New Jersey. It is also found off the coasts of Greenland, Iceland, Japan, Russia, the United Kingdom, and Portugal.