Japan — nori cultivation began in Edo (Tokyo) Bay in the 17th century, where fishermen discovered that seaweed spontaneously grew on bamboo poles placed in shallow water during winter. The systematic cultivation method (nori-hibi, seaweed nets) was developed in the 18th century. The Ariake Bay nori industry expanded dramatically in the post-war period with the development of the artificial spore-seeding technique.
Nori (海苔, Pyropia yezoensis) is the dried seaweed sheet that is inseparable from Japanese food culture — used for wrapping onigiri, forming the exterior of maki sushi, as a soup garnish (yakisoba, ramen), as the base of temaki hand rolls, as a flavouring in furikake, and as a toasted snack (yaki-nori). Japan cultivates nori in shallow coastal nets (nori-hibi) primarily in Ariake Bay (Saga and Fukuoka Prefectures) and Tokyo Bay coastal areas, with Ariake nori considered the premium category. The nori cultivation cycle: spores released into the water in autumn; harvested in spring after the nori blades have grown to the ideal size (about 20cm length for optimum flavour and texture); dried, pressed into sheets, graded and packaged. Premium nori is graded on colour (black-purple vs brown), aroma (when toasted), and texture.
Fresh-toasted premium nori's flavour is of concentrated sea — a complex, deeply marine, slightly sweet, mineral character that is immediately distinct from lower-quality nori's flat, salty character. The toasting releases the volatile aromatic compounds that give high-quality nori its distinctive smell. Around sushi rice, the nori softens and releases its marine character into the rice — the combination of nori's oceanic depth and the vinegared rice's clean acidity is one of Japanese cuisine's most perfected flavour pairings.
Premium nori characteristics: deep black-purple or near-black colour (indicating optimal harvesting time and processing); smooth, evenly textured surface; distinctive, aromatic smell when raw (like fresh ocean); crisps immediately when heated and snaps cleanly rather than tearing. Toasting nori (yaki-nori): pass each sheet 3–4 times over a low gas flame at close distance (10–15cm) until the sheet becomes slightly green-tinted and fragrant — do not brown or char. The toasting activates the aromatic compounds and drives off moisture, producing the characteristic crisp texture. Nori seasoned with soy sauce and sugar (ajitsuke nori, 味付け海苔) is a different product — more commonly used for breakfast rather than sushi.
The Ariake Bay nori season (first harvest, 'ichiban nori', in January) is Japan's nori equivalent of Beaujolais Nouveau — the season's first harvest, made from the youngest, most tender nori blades, has a specific delicate sweetness and complex marine character unavailable in later harvests. Premium Tokyo Edomae sushi restaurants (Sukiyabashi Jiro, Sushi Saito) source ichiban nori from specific Ariake producers and store it in humidity-controlled environments. When wrapping temaki (hand rolls): the nori should be eaten immediately after rolling — the moisture from the shari (sushi rice) softens the nori within 30–60 seconds, changing the textural experience from crispy to chewy.
Storing open nori without re-sealing — nori absorbs moisture from the air within minutes and loses its crispness. Toasting nori too close to the flame or holding too long — burnt nori develops a bitter, acrid character. Using ajitsuke nori for sushi — the sweetened seasoning disrupts the balance of the sushi preparation.
Washoku — Elizabeth Andoh; Japanese Cooking: A Simple Art — Shizuo Tsuji