Seaweed Basics

Seaweed is the name given to a group of algae that grow in, or near, salt water or freshwater. Seaweed can grow in warm, temperate, or cold water.

Seaweed has no leaves, stems, or roots. The body of seaweed, which consists of nonvascular tissue, is referred to as the thallus, a term derived from the Greek word thallos, meaning “green shoot.” The size and shape of seaweed plants are determined by their habitat. The plants found in warm seas are grasses or bushes that rarely grow to heights of more than 12", whereas seaweed that grows in colder waters is lush and can range from 3–33 feet in length.

Seaweed has been eaten since ancient times in certain parts of the world, mainly by the inhabitants of coastal regions in northwestern Europe (Scotland, Ireland, Norway, Iceland); Hawaii; South America; the Pacific islands; New Zealand; and Asia (especially in Japan, China, and Korea). Archeological evidence found in Japan suggests that seaweed has been part of the human diet for at least 10,000 years. Today the Japanese eat more seaweed per capita than people of any other nationality, and Japan is the world’s leading producer and exporter of seaweed. This explains why individual varieties of seaweed are often referred to by their Japanese names, such as kombu, wakame, hijiki, and arame.

Seaweed comprises of almost 25,000 different species, but only about 40–50 species have a pleasant taste. These edible varieties belong to one of three groups: brown algae, green algae, and red algae.

Brown algae, also known as brown seaweed, is the most abundant and most commonly eaten variety. It is brown in color because yellow and orange pigments known as xanthophylls mask the green color of the algae’s chlorophyll. Species of brown seaweed harvested in Japan include arame, hijiki, kombu, and wakame. Kelp is the most common variety of brown seaweed in North America. Brown seaweed grows at moderate depths.

Green algae, also known as green seaweed, grows to be 2–4" long and generally has a delicate taste and texture. The chlorophyll in green algae is not masked by other pigments, which gives these plants their vibrant green color. Among the most popular varieties of green seaweed is sea lettuce, which looks and tastes somewhat like actual lettuce.

Red algae, also known as red seaweed, is colored by a red pigment known as phycoerythrin that masks the green chlorophyll. The numerous algae classified as red seaweed include dulse and carrageen.