Seaweed
Aosa
a bright green seaweed that thrives where fresh water meets the sea
A green seaweed that thrives in brackish water near river mouths. Dried, it turns deep green and is used as a briny-aromatic garnish in soup, tempura, and to finish okonomiyaki; fresh it is quite bitter, so it typically circulates dried.
What it's made of
A green algae found widely in brackish water near river mouths worldwide, some varieties of which are said to have leaves too tough to eat fresh. Dried, it turns a deep, vivid green and is used as a briny-aromatic garnish to finish soups, tempura, and okonomiyaki — rarely the star of a dish, yet able to shift its character by scent alone.
How it's made
After harvest it is sun-dried and crumbled fine, distributed as a sprinkle-on "aonori" garnish — the standard processing method. Since some varieties keep a lingering bitterness fresh, it is only after this drying step that it becomes usable as an everyday seasoning, the drying itself concentrating its aroma enough to work in a small pinch.
Why it took this shape
About seven-tenths of Japan's harvest is said to come from Mikawa Bay in Aichi Prefecture, with the rest gathered in Okayama and Tokushima. Growing only in the narrow band of brackish river-mouth water is thought to be one reason it settled into the role of a dried garnish shipped elsewhere, rather than a fresh vegetable eaten on the spot — its poor keeping quality fresh arguably deciding how it would be used.
Dishes in the same style
- Hidaka KonbuFormally called mitsuishi kelp. Softer and quicker-cooking than other kelps, sometimes called "fast-boiling kelp"; the spent strands are easy to eat as a simmered side after making dashi, making it a household all-rounder.
- HijikiA brown seaweed that grows on rocky shores, brown when fresh but drying and processing into small black strands and pellets. Simmered, it carries a distinct briny aroma and a mineral-rich crunch, classically cooked with soybeans and carrot.
Ingredients and dishes from this land
Known source
- Known source: Aichi, Nishio
Mikawa Bay around Isshiki port is one of Japan's leading producing areas.
- Known source: Okinawa, Naha
In Okinawa, called "aasa," it is a familiar staple in soup.
Contrast
- WakameA brown seaweed used widely in miso soup and salads. Its thickness and bite are said to vary with the strength of the local tidal current, turning bright green when briefly dipped in hot water; fresh spring wakame is said to be most aromatic.
- MozukuA thin, thread-like brown seaweed with a pronounced slipperiness, typically eaten in a light vinegar dressing for its smooth slide and briny aroma. Nearly all of Japan's farmed supply comes from a single prefecture, also used in tempura and rice porridge.