Guide to Edible Seaweed

Although all marine algae contain chlorophyll, they are distinctly colored by pigments. The variety of their coloration is so great that pigmentation plays an important role in marine algae classification.

Brown Algae

The color, which ranges from brown to muddy yellow, comes from the pigment fucoxanthin. Although this group includes some small, almost microscopic members, larger seaweeds with leathery textures predominate. The variety of shapes ranges from several-hundred-feet-long kelps, to whiplike fronds, to leaflike structures of one to three feet in diameter. All large brown algae (this includes several genera of kelp, plus rockweed and sargassum) anchor themselves to rocks. This anchoring is accomplished by means of holdfasts, which are structures similar in appearance to roots of land plants. Their tough outer layer renders them relatively immune to being rubbed by fish and to the beating they receive when they’re broken off and washed ashore. They’re held upright by hundreds of air bladders. There are approximately 1,000 species of brown algae.

Red Algae

On the whole, the red algae are smaller than the browns. They’re also more delicately shaped, often appearing as graceful, branching ferns in hues ranging from violet, to red, to purple, to pink. Some are lance shaped with wrinkly margins; others have wide elastic fronds and look like sheer sheets of plastic with ruffled margins. Some grow as thin filaments or leaflike structures. The reds include Irish moss (Chondrus crispus), laver (Porphyra spp.), dulse (Rhodymenia palmata), and Grinnellia. There are approximately 2,500 species of red algae.

Green Algae

These also grow as filaments or branching fronds. The most commonly eaten seaweed in this group is sea lettuce (Ulva lactuca). Most green algae are found in freshwater. There are approximately 5,000 species of marine green algae.

Once washed ashore, seaweed seems to be nothing more than gooey, smelly, fly-infested garbage. However, as unpalatable as they might seem, seaweeds are, in fact, extremely important plants. They’re not only nutritious eaten as is or lightly cooked; they’re also usable for many nonfood aspects of survival, for example, in fertilizers, paper, binding pills together, and nutritional supplements.

Stems: Seaweeds contain no stems in the botanical sense of the word. The section in seaweed that resembles land-plant stems is called the stipe.

Leaves: Technically, seaweeds contain no leaves. However, to the layperson’s eye, many seaweeds appear to be one large leaf, or expanded flat leaves or ribbons. Other seaweeds have the appearance of a head of lettuce. In the brown algae group, the part of the seaweed that resembles land-plant leaves is called the lamina. This is where photosynthesis occurs.

Roots: Seaweeds contain no roots. However, many seaweeds have a specialized region that enables them to attach to rocks. These are called rhizomes, horizontal-growing stemlike growths, which act much like the rhizomes of land plants. These rhizomes grow rootlike tough fibers called holdfasts, which anchor the seaweed to rocks.

Reproduction: Seaweed reproduction occurs in one of three ways: 1) by the division of the whole body of the parent plant (vegetative reproduction); 2) sexual reproduction; or 3) asexual reproduction.

Health Benefits of Edible Seaweed

Edible Properties of Seaweed: Although the conspicuous red, brown, and green marine algae are, for the most part, a safe group to consume, botanists disagree as to exactly how safe. Some believe that seaweeds are completely nontoxic (which doesn’t mean they are edible). Others point out that certain known macroscopic species of these three groups of marine algae are toxic to other marine life, and thus humans should exercise caution. Furthermore, the seaweeds have not all been studied adequately to simply recommend eating them unreservedly. Becoming more specifically acquainted with individual seaweeds certainly seems appropriate. Books that are useful in this regard are:

Stalking the Blue Eyed Scallop by Euell Gibbons
Seashores: A Guide to Animals and Plants along the Beaches (A Golden Nature Guide) by Herbert Spencer Zim and Lester Ingle
Seaweeds and Their Uses by Valentine J. Chapman
The Seavegetable Book by Judith Madlener

Some seaweeds are simply unpalatable due to their rubbery texture and rigid structure, which can be overcome by drying and powdering or by various cooking methods. What works for one seaweed may not work for another. Where possible, talk to the local people who use seaweeds. Only by experience will you be able to learn which seaweeds are more palatable than others. As you experiment, don’t rely only on your taste buds’ first reaction—try ingenious ways of using seaweeds.

Generally, seaweeds are used

1) for food directly (eaten raw, dried, cooked into soup, and so forth);

2) as a seasoning and/or flavoring (due to their salt and minerals);

3) in any food product requiring thickening, smoothing, or jelling, such as candies, jellies, puddings, ice creams, and gravies; and

4) as a combination steaming/flavoring agent in clambakes.

Some of the tastiest seaweeds are dulse, laver, sea lettuce, kelp, and Irish moss.

Those seaweeds that can be eaten raw can be either eaten fresh (from sea or beach) or dried first and then chewed like jerky. Boiling is preferred in some cases where the seaweeds are bone-dry. Others become more palatable after cooking (up to 30 minutes) in water; both the resulting broth and the seaweed will usually be very good. When the broth cools, it will normally gel, making it useful in various dessert items.

Dried and powdered/shredded seaweed is an excellent item to carry in your survival pack. Placed in a pot of water with other wild vegetables, seaweed makes the closest thing to instant soup that’s available from the wild.

Most of the hollow stalks and air bladders of the brown algae can be eaten raw or pickled. I’ve tried the following recipe with the air bladders of the Pacific Coast kelp and found it delicious! Pack approximately 100 raw air bladders (alone or with other pickling vegetables, such as cauliflower, onion, and sliced carrot) into clean quart jars. Add apple cider vinegar until the air bladders are nearly covered, and then add one to two tablespoons of cold-pressed olive oil. Sprinkle in your favorite pickling herbs (such as dill seed, tarragon, and celery powder), and add approximately 10 freshly sliced garlic cloves. Cap tightly and shake once or twice a day for a few days. These air bladders can then be eaten as is or as a side to Mexican dishes as a chili pepper substitute.

Many seaweeds can serve the same thickening function as okra does in soups. Tender seaweeds can be added directly to soups; the less tender seaweeds are better broken into bits, blended in an electric blender to a fine mush, then strained through a fine mesh or muslin cloth to remove the solids. Then bottle, label, and refrigerate. This liquid can then be used as the soup or gravy base, substituting for flour. The strained-out pulp also has many uses—it can be cooked into homemade ice cream as a smoother/stabilizer, can be used for compost, mulch, or earthworm food, or can be added to animal foods.

The algin that is used to smooth commercial ice cream is obtained from brown algae. Algin is also used as a thickener or smoother in many other foods, such as puddings, jellies, and candies. In packaged foods, the ingredients alginate, alginic acid, and carrageenin are all seaweed derivatives.

Seaweeds have long been used in clambakes. When heated, they give off a steam that adds flavor to other food being cooked near them. Thus, seaweed is thrown directly into large fire pits next to meat, seafood, potatoes, corn, and so on. Seaweeds can also flavor and help steam foods at home if you add a layer of them to both the bottom and top of any large pot or roasting pan containing meat or vegetables.

In 1958, wilderness expert George L. Herter wrote in his Professional Guide Manual about some of the freshwater green algae. Herter writes:

Pond scum or green algae is a wonderful food eaten either in liquid or dried form. Green algae, which makes up the scum, contains more than 50 percent easily digestible protein. This is more than potatoes or wheat. Dried green algae tastes like raw Lima beans or pumpkin. Pond scum soup or liquid green algae has a raw pumpkin-like taste. You can stay healthy and even put on weight on a diet of green algae. If the ponds are frozen over, simply chop out some of the frozen pond scum and melt it over a fire.

The Japanese, as I write this in 1958, are leading the world in producing food from algae. They are now mass producing an artificial food called chlorela. This food is made entirely of algae. Twenty five grams of chlorela powdered is equal in nutrition content to 1.5 bottles of milk, 1.2 eggs, or 25 grams of roast beef. Algae today are the world’s most important single item. Algae are far more important to the world than atomic energy. Atomic energy can create power and heat but cannot produce food. Algae can create food in unlimited quantities and can go on creating it with no loss to the parent stock and with no raw materials except water and sunlight. The more impure the water, the faster algae grow and multiply. As for energy, algae can produce more usable energy than any substance in the world.

With ten dwellings to the acre, the whole population of the earth could be housed in an area the size of Kansas. By raising algae in the remaining area of the state, enough food could be produced to feed over ten times the people that now live in the whole world.

When people foolishly talk about food shortages in this world, just remind them of these proven facts.

George Herter wrote these words over 50 years ago, and the booming world population has undoubtedly altered his figures. Nevertheless, his message is an extremely important one.

I’ve eaten fresh green algae from mountain streams many times. The flavor is bland, with a somewhat crisp texture. On July 3, 1982, I tested some methods of preparing green algae. I collected fresh green algae from Eaton Canyon on Pasadena’s east side, washed them, and then sautéed them in oil. The algae nearly liquefied. The flavor was acceptable, though somewhat bland. John Watkins of Harbor City suggested that I first dry the green algae and then sauté it. The final product would be very similar to eggs.

Interestingly, a bottle of “spirulina” pills sells for nearly $10. Spirulina is actually a blue-green algae. While spirulina is excellent nutritionally, so are most of the thousands of freshwater green algaes. Rather than give away my hard-earned dollars, I prefer my green algae fresh!

Medicinal Uses of Edible Seaweed: Most iodine is obtained from two sources: brown algae and red algae. Iodine, necessary for the proper functioning of the thyroid gland, has been used for the treatment of goiter for over 5,000 years. Goiter is an enlargement of the thyroid gland, visible as a swelling on the front of the neck.

In his book on nutrition, Are You Confused?, Paavo Airola lists kelp as 1 of the 10 plants that help the body’s glands reach their peak of healthy activity. Many seaweeds—most commonly kelp—when powdered yield potassium chloride, a salt substitute. This is a godsend particularly for those who must restrict the amount of sodium chloride in their diet. By dry weight, kelp is about 30 percent potassium chloride.

Red algae is the source of agar (also called agar-agar), used for the laboratory culture of bacteria. Algin, from brown algae, is used in many medicines such as cough medicines and laxatives. The gelatinous material extracted by boiling seaweeds can also be used as a remedy for burns and bruises or as a hand lotion.

One hundred grams of dulse contain 3.2 grams of fat, 296 milligrams of calcium, 267 milligrams of phosphorus, 2,085 milligrams of sodium, and 8,060 milligrams of potassium. One hundred grams of Irish moss contains 1.8 grams of fat, 2.1 grams of fiber, 17.6 grams of ash, 885 milligrams of calcium, 157 milligrams of phosphorus, 8.9 milligrams of iron, 2,892 milligrams of sodium, and 2,844 milligrams of potassium. One hundred grams of kelp contain 1,093 milligrams of calcium, 240 milligrams of phosphorus, 3,000 milligrams of sodium, and 5,273 milligrams of potassium.

Other Uses: Pacific seaweeds, mostly brown algae, have been used as a source of potassium for fertilizer. Ernest Hogeboom, formerly a professional gardener in Pasadena, California, once showed me his “secret” fertilizer. Into a 55-gallon drum he emptied several trash bags full of kelp, then filled the drum with freshwater and put on the lid. As the seaweed began to decompose, it colored the water dark brown. Within about two months, almost all of the seaweed liquefied. This liquid was used as a fertilizer concentrate, which Ernest diluted with freshwater before using on customers’ plants.

When Dolores Nyerges operated her organic and natural gardening business, she made her own fertilizer, similar to the Hogeboom secret formula. Dolores filled a 55-gallon drum with seaweed and water, and let the seaweed rot. When she removed some of the very smelly liquid, she added about a cup of fish emulsion per five gallons of the liquid. This was then used as a root fertilizer, but more often applied as a spray on the foliage of the trees and shrubs. When sprayed onto the plants, Dolores noted that unwanted bugs and insects were also kept away.

The liquid that is extracted by grinding seaweed in a blender and straining out the pulp can be used for a mineral bath. Diluted until there’s no ocean odor left, it can be used as a water softener for doing the laundry, enabling you to cut back on soap about 30 to 40 percent.

The long flat stipes of some seaweeds, if treated with a leather softener such as Stock Slick, can be used as an interim lashing/binding material (preferably in places where they won’t get wet). The long hollow stipes of some of the kelps have been used as fishing lines for deep-sea fishing by Native Americans in Alaska. These same stipes, along with any of the stringy segments of seaweeds, can, if the need arises, be woven into moccasins, mats, baskets, and pot holders, and even be used for short-term furniture and clothing repair.

Algin from brown algae is used as an additive to hand lotions, inks, and dyes. Thousands of tons of kelps are used annually in the chemical industries.

Detrimental Properties of Edible Seaweed

Be certain that the seaweed you gather for food hasn’t been sitting on the beach long enough to begin rotting. Seaweed that has already begun to decompose contains bacteria that will cause sickness if eaten.

Any seaweeds growing near a sewage effluent or by mouths of rivers, bays, or inlets where pollution is being dumped readily pick up the toxins in their bodies, and thus become “poisonous.” Such seaweeds should not be eaten. Don’t collect seaweeds for consumption after an oil spill.

Be sure to thoroughly wash your seaweed before consumption. This eliminates any adhering sand and potentially harmful substances. A suggested method, especially if the purity of the ocean water is questionable, is to wash the seaweed in your bathtub or sink. First wash in hot water with a small amount of biodegradable soap, then drain. Repeat the wash and drain process three times in the hottest tap water possible. Finally, rinse at least once in unsoapy water. Then you can dry the seaweed or cook it into a variety of recipes.

Where Edible Seaweed Can Be Found

By definition, seaweeds are the brown, red, and green algae found in marine waters. Brown algae thrive on the East and West Coasts of the United States and in many other oceans of the world. Red algae is most abundant on rocky coasts of warm water on both the East and West Coasts. Green algae are more commonly found inhabiting fresh or brackish waters. The greens that are found in marine waters are found along both the East and West Coasts, most abundantly in warm waters.

Growing Cycle of Edible Seaweed

Many seaweeds are perennials. They are easiest to gather at low tides. Some are better quality in the spring; others are equally good gathered throughout the year. Often one can ask the locals which seaweeds are the best in the area, and when the best time is to gather them.

Ocean waters near any of the world’s major population centers may indeed be toxic, but not because of the salt. Various forms of urban waste water routinely flow into oceans worldwide. Such wastewater can contain biological contaminants and dangerous chemicals. The water can be bad as much as two miles out to sea, especially during and immediately after rainstorms, when the water treatment systems are unable to handle the increased water flow. During such circumstances, all forms of waste flow directly into the ocean, untreated.

More from Guide to Wild Foods and Useful Plants

• The Benefits of Wild Edibles
• Guide to Wild Manzanita
• The Health Benefits of Ribwort
• Using and Eating Piñon Pine
• Using and Eating Prickly Pear

Reprinted with permission from Guide to Wild Foods and Useful Plants: Second Edition by Christopher Nyerges and published by Chicago Review Press, 2014. Buy this book from our store: Guide to Wild Foods and Useful Plants, Second Edition.