Kombu are harvested on the coasts of Hokkaido, the northern island of the archipelago and in Tohoku, the north-eastern part of the main island of Honshu. There are various species of algae. Among them, those most commonly used for dashi (Japanese stock) are makombu, rishiri-kombu, rausu-kombu. Hidaka-kombu is simmered with seasonings to be used as side dishes such as simmered kombu and takiawase. Kombu for dashi is grown for two years and harvested from July through September. Kombu is abundant in the umami substance glutamate.
Levels of naturally occurring glutamate（mg/100g）：