A Seaweed Primer: How to Use Kelp, Nori, Wakame, and More

A guide to sea vegetables and their applications in the kitchen, from bacon-y dulse to plump, briny sea beans.

Dr. Prannie Rhatigan stood in my kitchen contemplating the emerald-green whirlpool of smoothie in my blender. Over the din of the machine, Ireland’s leading seaweed expert waxed poetic about the deliciousness of dulse as she fed the burgundy-colored dried strands, along with spinach and fruit, into the machine. Dulse was new to me, so I paid close attention as she picked out the occasional micro seashell riding sidesaddle on the leathery ribbons of seaweed. While I knew the dulse would turn my usual breakfast into a nutritional powerhouse, I wasn't quite prepared for the subtle salinity and umami roundness it added—this was some next-level smoothie work.

I met Prannie in 2010 when she was in Seattle on book tour for her exceptional cookbook, Irish Seaweed Kitchen. Seaweed is commonly associated with Chinese, Korean, and Japanese cuisines, but Ireland, England, and Wales also have a long history of incorporating seaweed into their diets. On this side of the pond, Native Americans on the Atlantic and Pacific coasts have used seaweed as food for thousands of years. But most of the rest of America had little working knowledge of the wealth of potential food growing up and down our coastlines until recently, when coverage of seaweed's culinary uses hit the mainstream media. Sushi might have brought seaweed, and specifically nori, into America's consciousness, but there are dozens of other seaweeds to explore.

What Is Seaweed?

Seaweed is a colloquial term that refers to red, brown, and green algae, though it’s about as helpful a term as “landweed” would be to describe lettuce, arugula, and kale. For many people, the thought of seaweed conjures up scent memories of the slimy stuff washed up on the ocean shore. But judging these diverse and flavorful organisms by such bedraggled specimens is as unfair as judging land vegetables by the contents of your compost pile. Seaweed for eating is fresh and lovely, like a piece of perfectly plucked lettuce, and just as you wouldn’t want to eat spoiled lettuce, so would you avoid seaweed that’s sitting on the sand.

One of the most widespread seaweeds is kelp, which can be found up and down the Pacific Coast in dense liquid forests that are as impressive as stands of redwoods, yet largely invisible to most beachgoers and boaters. Kelp and all other seaweeds (or, as I prefer to rebrand them, “sea vegetables”) can be harvested year-round, but should be gathered only in areas of low industry, low population, and good water flow to avoid contamination from other sources. Additionally, make sure to check any warnings posted on the beach—the same so-called “red tide,” or algal blooms, that makes gathering shellfish risky can also contaminate seaweeds. In any event, rather than scraping up the lonely stragglers close to the shore, gathering kelp is best done by boat or kayak.

Which is what I was doing when, a year after meeting Prannie, I found myself leaning precariously over the edge of a kayak off the coast of Lopez Island, Washington, hauling onboard an 11-foot blade of kelp and slicing it off with a pocket knife. Jennifer Adler, a chef and nutritionist, was showing me and a dozen other people how to sustainably harvest a variety commonly known as “edible kelp” or “bull kelp.” It can grow to a height of 118 feet and consists of a holdfast (a root-like structure that secures the base to the ocean floor) and a single stipe (stalk) topped with a ball full of carbon monoxide, which allows the kelp to float toward the light. From this gas ball emerge dozens of blades. Each of us was encouraged to take home at most six of these blades, enough to last one person a year.

Once you’ve clipped the blades, the next step is to dry them. For me, that meant toting bags of kelp home to Seattle and awkwardly draping the blades over the balcony while my neighbor stared at me, equal parts bemused and concerned. If any moment could stamp me as a ready-made extra in a Portlandia sketch, this was it. After it had dried, I snapped the pieces into small shards and ran it in batches through my spice grinder, creating a powder that would become a key ingredient in my kitchen for the next year. Along with adding potent savory flavor and natural salinity, the ground kelp also furnished me with valuable nutrients—seaweed is known for its high calcium and iodine content, as well as fiber—thus killing three birds with one stone.

For that matter, if your food needs a flavor boost, all varieties of seaweed are high in glutamates (the stuff of MSG, but in a less isolated form), making them, like fish sauce or Worcestershire sauce, a handy tool to keep in your arsenal of umami bombs. And, like those liquid ingredients, sea vegetables can lend savoriness to your food without overtaking the dish with their flavor: A mere pinch added to soup, salads, or smoothies will be nearly undetectable to your palate for what it is, but you’ll notice the instant flavor enhancement.

If, as is true for most of us, harvesting your own kelp doesn't seem feasible—or sound like your idea of a good time—both cultivated and wild sea vegetables are easy to find online, in natural-foods markets, and in Asian groceries. While you can do as I did and make a powder out of your favorite type (add dried porcini mushroom for an even more complex flavor!), most seaweeds can also be purchased in ready-to-use flake or powder form.

Like shellfish farmers, sea-vegetable harvesters need to be advocates for clean water, and the best brands test for contaminants and harvest responsibly. I recommend Eden Foods and Maine Coast Sea Vegetables for their high-quality flavor and commitment to sustainability.

To help you get started adding sea vegetables to your cooking, I’ve profiled five of my favorites, all easily purchased in dried form, plus a few more obscure ones if you want to delve deeper.

Nori

Nori is the gateway seaweed: crisp, relatively mild, slightly saline, with roasted, smoky, nearly nutty notes. High-quality nori is smooth and uniform in texture, with a dark-green color. Avoid nori that is splotchy, crumbly, pale green, or reddish. Store it in airtight packaging, and, if you won’t get to it within a few weeks, double-bag it and pop it in the freezer, where it’ll maintain its freshness for about six months. For optimal textural quality, pass it quickly over an open flame to re-crisp and refresh just prior to using.

Most of us know nori from makizushi (sushi rolls) and nigiri (raw fish on sushi rice), but there are dozens of other uses for it. As a grain-free wrap, it’s a convenient way to transport tasty fillings. Roll up some quickly scrambled eggs with spinach and avocado in nori sheets, then add a bit of hot sauce for a simple breakfast to go. Pass nori sheets briefly over an open flame, brush with sesame oil, and sprinkle on some salt, then cut it into smaller rectangles for snacks. Break it up into small pieces and top rice with it, along with kimchi and a fried egg.

Kelp/Kombu

Kelp is notoriously meaty and valued for its concentration of umami. While there are many subspecies in this category, you will usually see it marketed as either “kelp” or “kombu” or both. Kombu is the Japanese word for kelp, most typically the Saccharina japonica species. (In Korean cooking, kelp is called dasima, and is an essential ingredient for making broth.)

Kelp’s powerful umami flavor is perhaps most prominent, and certainly most ubiquitous, in the savory broth called dashi, the foundation for Japanese cuisine. In fact, it was the kombu in dashi that, in 1908, led Japanese chemist Kikunae Ikeda to discover and name the flavor we call “umami” in the kelp’s glutamates, resulting in his creation of MSG.

You will often see a dusting of white powder on kelp. Personally, I don’t rinse this off, in order to avoid losing the amino acid glutamine, the main component in kelp’s savoriness. However, it should be noted that wiping before use to remove any particles of dirt or other contaminants is a common step in Japan, whose cooks are, of course, among the world’s most prolific users of kelp.

Like many other seaweeds, it will become damp if exposed to air, so store your kelp in a well-sealed container. If it does accumulate moisture, you can sun-dry it or put it in a 200°F (90°C) oven until it’s brittle.

Adding kelp to dried beans can enhance their flavor—and may even help tenderize the beans, as Cook’s Illustrated has found. Sandwich raw fish fillets between two pieces of kelp and refrigerate for an hour or two to firm up the flesh and add umami, then cook as you would usually do. Or, leave sashimi-grade fish sandwiched in this way in the fridge for several days as a delicious way to cure the fish; slice thinly, then eat raw.

Kelp is much tougher and thicker than other seaweeds and can lend a satisfying density when added in small amounts to salads. Simply rehydrate until soft in cool water, then drain and slice. Or, better yet, using a knife or scissors, thinly cut the “spent” kelp you’ve used for dashi or cooked with beans, and add it to your salads, rice dishes, or soups.

Wakame

Wakame is a delicate, lightly sweet seaweed, often used raw and rehydrated in salads and miso soup. Because of its silky, satiny texture, I find it important to pair wakame with ingredients that have some crunch or chew, like pink shrimp or cucumbers in a Japanese sunomono salad, for better balance. Add some to massaged kale salads along with avocado, toasted sesame seeds, and lightly pickled red cabbage or kraut. Or try using it in sesame oil–flavored cold noodle salads, or in chicken soup.

Wakame is very similar to another seaweed called Alaria, which makes a good substitute if wakame is unavailable where you live, though Alaria is a bit tougher.

Dulse

Dulse is by far my favorite seaweed. It has a chewy, fruit leather–like texture and a deeply savory, bacon-y flavor that’s especially enjoyable when it’s pan-fried over medium-high heat until crisp. In fact, this is the only type of seaweed that I enjoy eating nearly unadorned, at times right out of the bag. It’s saltier than nori, so you may not need any additional salt when using it in your food. Dulse has also been used as a substitute for chewing tobacco, probably due to its leathery texture and rich, deep aroma—though, admittedly, I don’t carry a tin of dulse chaw in my back pocket.

Cook up onions and salt them with dulse flakes, then use them to make baked beans or cassoulet, cioppino, or chowder. Add a scant teaspoon to smoothies. Crisp the dulse in a pan and use it in a sandwich with lettuce and tomato for a vegetarian take on a BLT. Make a seafood and sea-vegetable paella and crumble toasted dulse over the top, along with charred lemons and plenty of clams and mussels. Toast it and grind it in a spice grinder, then use it on top of popcorn, along with olive oil.

Arame

Arame is a mildly sweet kelp that looks like wispy, wiry strands of black vermicelli. Rehydrate it in warm water for five minutes, then toss the arame into salads with roasted kabocha or butternut squash, toasted pumpkin seeds, sesame oil, and rice vinegar; the color contrast between the black arame and the orange squash is especially appealing. When you’re roasting carrots, add rehydrated arame, along with grated ginger, in the last 10 minutes of cooking. Or, try stir-frying broccoli with oyster sauce and arame.

Arame is a close cousin (though thinner and more tender) of hijiki, a seaweed that's become controversial in recent years due to its high levels of inorganic arsenic. National food-safety authorities disagree over the risks of consuming hijiki—you can read up on the science here—but if you decide against it, arame makes a great substitute.

Other Sea Vegetables to Look For

Sea Lettuce

Essentially the salad greens of the sea-vegetable world, sea lettuce is tender, mild, and best eaten raw.

Ao-nori

Ao-nori is a bright-green, especially fragrant form of nori, commonly used in flake form and sprinkled (for example) over the savory Japanese dish okonomiyaki. I love to sprinkle it on soup or egg dishes, too; try it as a garnish on Daniel’s pork omurice with okonomiyaki sauce.

Ogo-nori

A red or purplish lacy sea vegetable with a snappy texture, most commonly seen in your bowl of tuna poke, ogo-nori is sometimes found fresh or dried in Japanese or Hawaiian markets, or online. Ogo can be pickled or used in salads or kimchi. Consider using it as a gorgeous bed to display raw oysters, too.

Sea Grapes

Sea grapes, also known as umibudo and sold fresh instead of dried, are a delightful sea vegetable that looks like tiny clusters of caviar, with the brininess of the sea and a satisfying pop. I use them as garnishes for seafood-based pasta dishes; you can also blanch and shock them to remove extra salt, then dip them in a citrus-soy sauce.

Samphire

Also known as Salicornia or sea beans, though it looks more like teeny-tiny bolting asparagus, samphire is a salty, snappy sea vegetable found in salt marshes. Like sea grapes, samphire is sold fresh. It's ideal when blanched and shocked in ice water, then heated gently with butter and served with fish dishes or in salads.

April 2018