Today we'll explain how best to grow this delicious vegetable. Negi is a Japanese bunching onion, which is grown very similarly to a leek. Negi is rarely grown outside Japan but is gradually becoming a specialty crop throughout regions of Hawaii and California as a versatile, international ingredient.
With Negi, direct seeding is a possible option, but generally, we recommend transplanting. When filling your seedling trays with soil it is important to remember two things;
- Make sure each tray cell is filled with soil from top to bottom. If a cell contains gaps without soil, this can create air pockets at the bottom causing the plant to dry out quickly and could damage the seedling’s root structure.
- Try to avoid packing the tray cells too tightly. Though the cells should be completely and evenly full, soil that is over compacted will make it difficult to remove the seedling for transplanting as you don’t want to snap the stem or tear roots. Not compressing or pushing hard on the soil after filling should help.
Try filling each cell from top to bottom, then giving the whole tray a careful shake from side to side to get air pockets out, then pour a little extra soil on the top to account for any settling.
When seeding in preparation for transplanting, you can plant up to three seeds per cell, no more than half (1/2) an inch deep.
Pruning & Preparation
Once the Negi has germinated, established, and reached five inches in length it is important to prune it. Prune the Negi plant back to four inches tall, taking one inch off the top to help stimulate plant growth and establish deeper roots.
Once the transplants are ready to be removed from the tray, separate the individual plants—if you opted for multiple seeds per tray—by gently pulling clumped plants apart and loosening any tangled roots, holding near the base of the stalk if possible.
Young plants need to be placed two inches apart when transplanting, and it is important to plant the bulb deep, nearly four to six inches into the soil, with only the green part of the stalk showing.
If you are a commercial grower with transplanting machinery capable of putting the plants that deep into the soil, you shouldn’t have an issue.
If you are hand planting, you can simply dig a shallow trench six to eight inches deep, placing the transplants in the lowest part. Don’t forget to maintain that two-inch spacing though!
Watering is very important. Negi, like most onions, requires a lot of water. Once the Negi plants are established, longer water sets—about three days a week—are preferable.
Cultivation and the piling up of soil around the base of the plant is your next priority. To establish the elongated white shank it must NOT be exposed to the sun. So the more dirt you push around the base of the plant the higher the white shank grows as it reaches for sunlight. Japanese Negi can typically grow anywhere most onions and garlic species are produced.
Negi can be harvested when reaching anywhere between 10 and 18 inches in length, depending on how much work you put into covering the base of the plant. Harvest when the fistulous layers form together and tighten. A gentle squeeze between thumb and forefinger on the stalk should feel dense, not spongy.
Negi can also stay in the soil for weeks after maturity, making them resilient in case of potential delays in harvesting.