The tasty Japanese seaweed nori is ubiquitous today, but that wasn't always true. Nori was once called “lucky grass” because every year's harvest was entirely dependent on luck. Then, during World War II, luck ran out. No nori would grow off the coast of Japan, and farmers were distraught. But a major scientific discovery on the other side of the planet revealed something unexpected about the humble plant and turned an unpredictable crop into a steady and plentiful food source.

Nori is most familiar to us when it's wrapped around sushi. It looks less familiar when floating in the sea, but for centuries, farmers in Japan, China, and Korea knew it by sight. Every year, they would plant bamboo poles strung with nets in the coastal seabed and wait for nori to build up on them.

At first it would look like thin filaments. Then, with luck, it grew into healthy, harvestable plants with long, green leaves. The farmers never saw seeds or seedlings, so no one could cultivate it. The filaments simply appeared every year. That is, they appeared until after World War II, when pollution, industrialization along the coast, and a series of violent typhoons led to a disastrous drop in harvests. By 1951, nori production in Japan had been all but wiped out.

Nori’s secret identity

Fortunately, on an island at the other end of Eurasia, Kathleen Drew-Baker had recently gotten fired. She had been a lecturer in botany at the University of Manchester where she studied algae that reproduced using spores rather than flowers. But the university did not employ married women. So when she got married to fellow academic Henry Wright-Baker she was kicked off the faculty and relegated to a job as an unpaid research fellow.

Drew-Baker focused on a type of nori unfamiliar to nearly everyone: Porphyra umbilicalis. It's a leafy seaweed that grows off the coast of Wales. Locals harvest it, grind it up, and use it to make bread or soup. Known colloquially as laver, it's still eaten in Britain but has not attained the international standing of nori.

Drew-Baker and her husband made a seaside lab where she could study its lifecycle. During her research, she noticed that she kept running across what seemed to be an entirely different species, known as Conchocelis. Conchocelis is a group of single-celled organisms that look like pinkish sludge and grow on the inside of abandoned shells. Drew-Baker noticed the pink sludge was especially common during the summer months, while the seaweed showed up during the winter months.

Eventually, Drew-Baker realized she was dealing with the plant equivalent of a superhero who is never seen at the same time as his alter-ego. These seemingly different species were actually the same. They were both a type of algae. In the summer, the leafy green seaweed sent out spores that collected and grew as the pink sludge in shells. In the winter, the pink sludge sent out spores that collected on debris (and bamboo poles) and built up into the seaweed again. In 1949, Drew-Baker published a paper in Nature detailing her discovery, "Conchocelis-Phase in the Life-History of Porphyra umbilicalis."

This might have been nothing more than a bit of trivia if it weren't for a second expert. Back in Japan, Segawa Sokichi at the Shimoda Marine Biological Station read Drew-Baker's paper and realized that what was true for Welsh seaweed was probably true for Japanese seaweed. The reason nobody had been able to find nori seeds was because they were looking for the wrong plant. And nori had stopped thriving of the coast because of disruptions to seabeds full of the shells where the pink sludge liked to grow.

Thanks to Drew-Baker's work, Segawa was able to invent the industrial process that lead to the stable, predictable production of nori, for which everyone with a taste for sushi should be grateful.

Seaweed goes high tech

Today, nori farmers leave nothing to luck. They still harvest the leafy stage of the seaweed from the sea. After that, technology takes over. Any spores grown by the leafy form of nori are chopped down to an ideal seeding length of 0.4mm. To encourage the spores to grow into their single-celled stage, farmers import shells from oyster fisheries, string them on fishing line, and hang them in huge vats of water that reproduce the ideal environment for the pink sludge to grow.

Inside the tanks, chlorine is added to the seawater to get rid of any harmful pathogens. It's filtered with sand to remove pollution. Industrial workers regulate the oxygen levels in the tanks and add in precise amounts of magnesium, sodium, iron, and potassium. Even the light levels are controlled. Indeed, nori farms only use the bottom shell of oysters because they are smoother and allow for more control over the level of light the Conchocelis spores are exposed to.

While the spores grow, a bit of biological engineering goes on as well. Each new batch of spores brought in from the ocean is sampled, cultured, and stored. Its production rate and the conditions under which it thrives are noted. As a result, researchers have identified spores that produce seaweed in waters of varying levels of saltiness, as well as various temperatures. With rising global temperatures, knowing which spores can survive best in warmer water will probably come in handy sooner rather than later.

Nori tanks also use temperature to induce the Conchocelis to move into the next stage of its life cycle. The waters are kept at summer-warm levels until it's time to harvest the spores that will produce seaweed. Then the facilities drop the temperature in the tanks to shock the Conchocelis into work.

An agitator encourages the release of the second set of spores and gets them swirling around the tanks. Most facilities have the agitation state timed to the minute. Then workers put nets into the tanks for "seeding." The nets are rolled onto human-sized spools to be sent to farms or stored in freezers until they're needed. At every stage they're checked for the quality and concentration of the spores on them. People no longer need to put bamboo poles in the ocean and hope for luck.

Drew-Baker's discovery was the first step toward the industrialization of a form of farming that seemingly couldn't be industrialized. Segawa and countless later innovators in Japan turned an unpredictable crop into a sure harvest. The application of technology to farming, especially this kind of farming, has entirely changed the game. Even the people involved in nori production have changed. While most types of fishing and farming are losing workers, nori farming keeps attracting young, technologically minded people. Seventy years after the nori farming industry was seemingly destroyed, it is thriving more than it ever has before.

Thanks to her many discoveries, Drew-Baker's career thrived, too. Despite being fired for getting married, she became the first elected president of the British Phycological Society in 1952. Today, Drew-Baker is known in Japan as "the mother of the sea," and every year a festival is held in her honor in Uto City.