Asago region is the main source of Iwatsu Negi, or green onion. It lies at the southern end of Tamba (northern Hyogo) and is part of the Chugoku Mountains, a mountain range in the Chugoku region of western Japan.
Maruyama River, which flows near the center, is known as an excellent source of water known as "Nattan no meisui".
Due to the geographical conditions, the climate on the Sea of Japan side and a coexisting inland climate, this region is known for its heavy snowfalls characterized by intense cold.
Only green onions grown in the town of Asago, Hyogo prefecture, are marketed under the name "Iwatsu Negi" and are available from late November to late March.
These green onion are rare. Grown in the town of Asago in winter, when the temperature difference between day and night is significant, these green onions are exposed to deep snow and frost.
These conditions give "Iwatsu Negi" green onions a unique softness, sweetness and tenderness.
The thick leaves are waterlogged, which is what makes "Iwatsu Negi" so soft and tender.
They can be eaten from start to finish, and the white part is particularly soft and sweet.
The colder it gets in Asago, the sweeter Iwatsu Negi becomes.