Columnist, Food

An underwater forest of green kelp stretches toward the light. Its rapid growth makes kelp and other seaweed a desirable crop; under optimal conditions it can gain nearly six inches a day. (Tammy616/Istockphoto)

Let’s say you want to farm. 

And let’s say there is a crop that requires you to plant and harvest, but do very little in between. It needs no fertilizing, no weeding, no watering, and it has very few enemies in the form of pests or disease. It gets all it needs from the environment around it and, under optimal conditions, can grow almost six inches a day. It’s healthful for people, and it actually leaves the environment better than it finds it. 

That’s the case in favor of seaweed, and it’s a case that Charlie Yarish, a professor in the department of marine sciences at the University of Connecticut at Stamford, has been making for nigh on half a century. They call him “Captain Seaweed.” I visited his lab, and I’m a believer.  

Yarish has spent decades doing the work that brings an interesting idea — let’s farm seaweed! — to the point where growers can start viable farms. There are some 3,500 kinds of seaweed, and figuring out which kind to grow, and where, and how, is a big job. The first rule? “Always grow a species native to the water you’re growing in,” says Yarish. Because some seaweeds are wildly invasive, that’s an important point.

One of the farmers who has taken advantage of Yarish’s research is Paul Dobbins. He’s a co-owner of Ocean Approved, a company that farms sugar kelp off the coast of Maine and sells it frozen, rather than dried. In a kind of busman’s holiday (I farm oysters), I went out with him to take a look at the kelp. It was early spring, and most of his crop had already been harvested, but he still had a line or two in the water. We pulled up to the buoy that marked a line, and he reached into the water. 

What he pulled into the boat was a remarkable abundance of plant. Sugar kelp gives magic beanstalks a run for their money: It can grow from seedling to 15 feet over one winter. In the process, it cleans the water by removing some of the nutrients that can lead to algae blooms. Along with shellfish, kelp is one of the few farmed foods with a positive environmental impact.


Paul Dobbins of Ocean Approved harvests sugar kelp off the coast of Maine. Seaweed can grow through the winter, so seaweed farming is a complement to most shellfish farming, which takes place in warmer months. (Sarah Dobbins/Ocean Approved)

And it doesn’t consume much in the way of resources. There’s the gas for the boat. There’s the labor in planting, harvesting and processing. And that’s about it.

There are a couple of ancillary non-environmental benefits. Most shellfish farming takes place from spring through early winter, so a crop that can grow from early winter through spring is an excellent complement; it can use both the space and the labor in the off-season. 

That same benefit makes kelp farming an easier sell to people who live in the area. Two objections to shellfish farming are that it’s unsightly and that it uses areas of water that people want to use for recreation. Because kelp grows over the winter, those issues are less important. In the Northeast, where I live and farm, many waterfront homes are occupied only seasonally, and homeowners look more kindly on a farm that operates only when they’re not in residence. 

Seaweed farms are good neighbors; they actually clean the water; and they require very few resources. Planet-wise, seaweed is a clear win. How about human-wise? Should we be eating more seaweed? 

Here in the United States, we’ve picked up what seaweed habits we have from Asians (miso soup, seaweed salad, sushi), who have a long seaweed-eating history. But where there’s sea, there’s seaweed, and coastal people around the world have used it for food, medicine and animal feed for millennia. Most of that seaweed wasn’t farmed but foraged, a practice that continues to this day all over the world. If you’re fond of the roasted pieces of seaweed that have become widely available as packaged snacks, take a look at the label: Some are made from farmed seaweed, others from wild-harvested. But there’s only so much we can take from the wild, and if we’re going to eat more, it makes sense to grow it.

The health impact of eating more seaweed isn’t so easy to figure out, because that word “seaweed” covers a lot of territory. Each of the thousands of species has a different nutritional profile. But we have to start somewhere, so let’s look at kelp. Compare the goverment’s nutritional data for kelp with the data for a nutritious terrestrial green — spinach — and you find that, gram for gram, the seaweed isn’t as nutrition-dense but is still a perfectly respectable vegetable and an excellent source of iron, folate and vitamin K.

Some scientists speculate that seaweed has benefits beyond the standard-issue list of nutrients and that more-obscure compounds might confer special advantages. Proteins, polyphenols and polysaccharides might help fight viruses, cancer or obesity. Alginate, a kind of fiber in seaweed, appears to block fat absorption. We don’t know much about any of this yet, but the possibilities are intriguing.

One well-studied aspect of seaweed is its iodine content. We all need trace amounts of iodine, and a deficiency results in goiter, an inflammation of the thyroid. Because iodine is added to most table salt, goiter is relatively rare in this country, but it’s still a problem in other parts of the world.  

Seaweed’s high iodine content is a double-edged sword. Just a bit of seaweed can get you the recommended 150 micrograms, but it might not take much more to get you over the recommended upper limit for adults of 1,100 micrograms. That much iodine can cause thyroid dysfunction.

Lots of factors affect iodine levels, which means farmers and processors have some control over iodine content. Species of seaweed, water temperature and salinity, and age of the plant all play a role. On top of that, at least a portion of the iodine in seaweed is water soluble, which means you can leave some of it behind in cooking water (although how much varies widely, which complicates the issue).

Although there are several ways to manage iodine content, seaweed still has a bit of a nutritional Catch-22. If you’re eating enough of it to get significant nutrition, you may also be getting too much iodine. If you eat smaller portions (like those roasted seaweed snacks, or the pieces in your miso soup), iodine isn’t a problem, but you’re also not getting many nutritional benefits. 


Chef Barton Seaver’s recipe for Moorish Stew replaces the traditional spinach with seaweed — or, as he likes to call it, seagreens. (Dixie D. Vereen/For The Washington Post)

And then there’s the taste, which is a bit of hurdle. Seaweed is, unfortunately, not delicious.  

It’s not terrible, either. It’s bland and a little salty. It tastes a lot like you’d expect a green that comes out of the ocean to taste: vaguely oceany. The texture, at least of the kelp that Ocean Approved grows, is crunchy, but not crunchy like apples or cashews or toast. It’s crunchy with a hint of soggy. Not bad, but not the stuff food cravings are made of. 

This, of course, is a judgment call, as assessments of taste always are, and I don’t expect anyone to take my judgment as the last word. So I asked Barton Seaver about the flavor of what he and other proponents have taken to calling “seagreens” in an attempt to make them sound more palatable. Seaver is a chef and sustainable-food advocate, and his latest book, “Superfood Seagreens: A Guide to Cooking With Power-Packed Seaweed,” is coming out in January. Advocate though he is, he’s upfront about seaweed’s . . . um . . . unfamiliarity. “We’re not used to the flavor,” he says. “The incredible umami-rich flavor of seagreens can be, quite honestly, off-putting at first. Seagreens need a more gentle introduction.”  

That part about umami is important. It’s the fifth taste, a hard-to-describe savory richness, and seaweed is rich in glutamate, a compound that imparts it. And so, even if seaweed’s flavor may not work well on its own, it can be an important addition to other dishes. Seaver suggests adding seaweeds to familiar foods — smoothies, salads, soups — rather than expecting it to stand alone.

As farmers and scientists experiment with different types of seaweed, flavor obviously will be one of the characteristics they look at, and it’s certainly possible that delicious varieties are in our future. Oregon State researchers recently announced that they had developed a type of dulse, a red seaweed, that tastes like bacon. Seeing as actual bacon has just been declared a carcinogen, this could be a BLT-saving development. 

All in all, seaweed isn’t my candidate for the new kale. Given that it’s an acquired taste, and that there can be some risk associated with high consumption, I don’t think it’s going to take dinner plates by storm. But when it comes to the problem of feeding 7 billion people, a nutritious green that grows all on its own — and requires no land, fertilizer or fresh water — ought to be part of the solution.

If that bacon thing works out, though, I’m all in.

Haspel writes about food and science and farms oysters on Cape Cod. On Twitter: @TamarHaspel. She’ll join Wednesday’s Free Range chat at noon: live.washingtonpost.com.