What is the seaweed commonly used in miso soup?

The seaweed commonly used in miso soup is wakame. This edible brown seaweed is usually sold dried or salted, then added to the finished soup, where it quickly softens and expands into tender, ribbon-like pieces.

Wakame has been cultivated in Japan since at least the Nara period, around the eighth century. Its Japanese name refers to “young seaweed,” and the species is scientifically known as Undaria pinnatifida. It has a subtly sweet flavor and a smooth, satiny texture that pairs well with tofu, scallions, and miso.

A common mix-up is kombu, another important seaweed in Japanese cooking. Kombu is primarily used to make dashi, the stock that forms miso soup’s savory base; wakame is the seaweed diners commonly see floating in the bowl. Nori, meanwhile, is the thin sheet seaweed used for sushi and rice balls, while hijiki is typically served as a simmered side dish.