Bunching Onions produce long edible leaves and stalks instead of setting bulbs. Bunching Onions really just describes a growing process rather than a type of onion. Any variety of onion can be grown as a Bunching Onion as long as the germination and growing conditions are right. There are two types of onions; long day and short day. Short day varieties need equal amounts of daylight and night to set bulbs and grow best in southern regions. Long day varieties need about 14 hours of daylight and 10 hours of night to set bulbs. Since you are growing Bunching Onions for their stalks and leaves, and not their bulbs, daylight hours do not really concern us. But you should still pay attention to the varieties which grow best in your area. In the north, grow long day varieties and in the south, short day.
In early January; sow Bunching Onion seeds indoors in trays in succession planting per week in 1” seedling trays. Sow Bunching Onions in soil that is 65o-85o F (depending on variety) at ¼” depth. It will take about 4-5 days to germinate. Transplant the seedlings into a bed or hot bed (again, depending on variety) 2 weeks after germination into soil that is 50o-65o F. Space each seedling only 1” apart and 2” between rows. You can also directly sow your Bunching Onions as long as your beds maintain a steady, optimal soil germination temperature. If you direct sow in succession, your Bunching Onions will be healthier and grow stronger. The last option is planting onion sets, which is a good option if you want to grow some onions for seed as these sets are a year old and ready to bolt, flower and set seeds.
Bunching Onions love sandy loam soil that is very fertile. Add another 1”-2” of compost into the soil before planting/transplanting. Do not fertilize during the growing season as it may stunt growth. The pH range should be 6.0-7.5. They need full sun and watering should be moderate and even at the base of the plant. Cover with a frost cloth until threat of frost is gone. During the cold months of January and February, also cover with a hoop house to trap in heat, uncover during warm days. Onions have shallow root systems. Water regularly at the soil line and mulch to maintain the soil’s moisture level. You will have enough Bunching Onions through spring. As you enter into the summer months, you may thin the Bunching Onions to 4” apart and 4” between rows. Your onions will continue to grow and form bulbs as long as you selected the right type of onion for your area.
Harvest Bunching Onion by pulling gently up by the roots. Bunching Onion can be a cut-and-come-again vegetable. Cut the leaves and stalk, leaving 2” of stalk and leaves. The onion will grow back again several times.
Grow at least 25 stalks of Bunching Onion for seed. Do not harvest any of the leaves or stalks from those Bunching Onion plants. Bunching Onion is a biennial, but if you planted onion sets the onion plant will flower and seed out. If you live a cool region, cut back the leaves to 6” from the bulb and dig up the bulbs, remove the dirt and store them between 32o and 40oF and replant in the early spring the following year. If you live in a mild region, cut back the leaves to 6” from the bulb, and cover with 6” of mulch. The plants will produce beautiful flowers, are insect pollinated with seeds in the summer. Remove the flower once it starts to dry and place in a paper bag for 2-3 weeks. Rub the flower heads over a screen to remove seeds from the flower.