Look at any coastal kitchen and you’ll find seaweed. In Peru, it tops the national dish (ceviche), in Scandinavia, you might see it in fiskesuppe (fish soup) or mashed into butter—not just on fancy tasting menus (Noma, ahem)—and in Japan, kombu is a pantry staple. The category of seaweed is a huge and diverse one. The word itself generally refers to marine macroalgae, ie, algae living in brackish water or salt water and visible to the eye. Scientifically speaking, that algae is broken down into three categories—red (Rhodophyta), green (Chlorophyta), and brown (Phaeophyta)—and if you can’t tell the difference, that’s because the colors are not actually determined by the leaves but rather by structures you can’t necessarily see.
Why eat seaweed at all? Not only is seaweed extremely nutritious for humans (it’s got protein, fiber, and a good amount of vitamins), but, when grown and harvested responsibly, it’s also a good-for-planet food source that gives more than it takes. A rich habitat for ocean life, it’s the foundation of the entire underwater ecosystem—think of it like the meadows and forests of the ocean, says Josie Iselin, author of The Curious World of Seaweed. It reduces carbon in the ocean and it regenerates naturally—no need for fertilizers, irrigation, or even land.
But while seaweed is getting a lot of recent hype as part of efforts to combat climate change, it’s been used to flavor and preserve for centuries. “Seaweed is part of our creation,” says Louis Trevino, co-chef and co-owner of Cafe Ohlone, a restaurant dedicated to preserving the culinary traditions of the Ohlone people in Berkeley, California. “It’s the latest thing that people look to as a sustainable food source, but it’s a food we’ve been eating for a long time.”
You don’t even need to live near the ocean to get it. For dried seaweed, simply head to your neighborhood Asian and Latinx markets and pick up a bag whatever catches your eye (kombu! dulse! gim!) and rehydrate before cooking. For non-dried stuff, check with your local specialty fish purveyor to see what they have or shop online (we like Monterey Bay Seaweeds and Atlantic Sea Farms). Eat it right away—most have a very short shelf life (a few days or so).
There is a big, umami-laden world of seaweed out there—nearly 12,000 species—but here are the ones we (and other food friends) love to cook with.
Seaweed aficionados know that the fresh stuff is pure luxury. Every coastal region specializes in different varieties—briny limu in Hawaii, tubular gutweed in Thailand—so seek out what is native to the area. But that doesn’t mean you should go to the beach and pluck out every seaweed in sight. “It is being overharvested,” says Nalani Kaneakua, a limu practitioner and founder of Koʻolau Limu Restoration Project in Kauaʻi. “We need to know how to harvest, to make sure there is lime left behind, and to pick without pulling the roots out.” Instead, chat with seaweed farmers, practitioners, and local seafood purveyors about how to purchase from or harvest with them (many offer workshops and seaweed-harvesting excursions).