Japanese onion, or negi, as they are called locally, are an important part of the Japanese diet. The vegetable has a long stalk and non-bulbous base, unlike normal white or brown onions grown in other countries. The relatively light onion taste of negi is somewhat similar to that of chives, but the plant itself is significantly larger.
Both the lower crispy section of the hollow green leaves and the solid white shanks are edible and are usually sliced for use as ingredients in a huge variety of common Japanese foods. In miso soups, within skewered yakitori sticks, with fish dishes, in ramen noodle soups and as strong tasting toppings and decorative finishes for tofu and sushi, to name a few.
Onions growing is therefore a large and important industry in Japan. The seasonal growing cycle runs more or less all year round, with planting and harvesting timed to occur at regular intervals during all seasons to maintain supply.
Japanese onion is an extremely hardy plant in general. While commercial growers tend to germinate seeds and develop seedlings in greenhouses to achieve maximum growth rates, the onion plant is capable of surviving both the extreme frosts and snows in Japanese Winters, as well as the heat and extreme humidity of Summer.
With the shortened days of sunshine behind behind them for another year, farmers are again busy planting seedlings out into the fields. At the same time, other farming families are also harvesting mature onion crops that have been left to develop throughout the slow growing Winter season.
Onion seedlings are usually germinated in greenhouses and then allowed to acclimatize to cold outdoor conditions before being moved to their final growing location out in fields. (Read about this hardening and acclimatization process in our earlier post.) The seedlings usually stand approximately 10-15cm (4 to 6 inches) high at this stage.
Before planting, the growing plots are usually flattened using tiller and then the soil is prepared with deep, evenly spaced rows. Pre-prepared trays of young seedlings are planted out between the row mounds with the aid of a specialized planting machine. The machine removes the seedlings from the flexible propagation trays, drops the seedlings down a chute and then lifts the soil to gently cover the roots.
Despite regular sunny skies that are good for onion growth, the late Winter season tends to see lower rainfall and cold prevailing winds that storm across the country from the plains of Northern China, Mongolia and Russia. The soil mounds help collect and retain any available moisture for the seedlings’ shallow roots and also shield against breakage and wind-chill burns.
There is still also high risk of frost and snow in late January in Japan, so after seedlings are carefully planted and tended to, they are covered with plastic frost tunnels. These plastic covers can either be sealed on very cold days and nights, or rolled up under clear skies to allow the warm sunshine to flood the developing plants.
While planting of onion seedlings continues, harvesting of mature crops also takes place. Specialized onion harvesting machines are commonly used to dig the plants from their (now) well packed growing rows. Their roots are then automatically de-soiled, cut and neatly wrapped into manageable bunches.
These field prepared bunches are then taken back to farmyard processing sheds in small flat top tray trucks for further processing. The onion stalks are separated, sized, partially striped of leaves, quality checked and then bundled with plastic tape according to strict wholesale market requirements.
*** Update: (July, 03 2013): More specific information about the onion harvesting process and the machines used can be found in our updated Summer post here.