noun
tree onion; Wakegi onion
A type of onion (Allium × proliferum) used as a vegetable, similar to a scallion but with a milder taste. Often used in Japanese cuisine.
わけぎを味噌汁に入れると、風味がよくなる。
Adding tree onions to miso soup improves the flavor.
このサラダにはわけぎが合う。
Tree onions go well with this salad.
ねぎ is the general term for green onion/scallion, while わけぎ specifically refers to the tree onion variety, which is milder and often used in specific dishes.
The name わけぎ is derived from 分け葱, literally 'dividing onion', referring to its growth habit of producing multiple bulbs. The exact historical origin is uncertain.