Guide to Growing Onions

By Ashleigh Smith

Onions are a staple in almost any kitchen, and for good reason. Not only do onions add flavor to your cooking, but nutrients too. They are known for their ability to lower inflammation and aid the immune system. The onion family Allium includes the common bulbing and bunching green onions, garlic, shallots, leeks, and chives.

Bulbing Onions - Allium cepa

The bulbing onion is probably the most popular allium alongside garlic. These are used in the base of thousands of recipes! In order to grow these delicious balls of flavor, you need to know a little more than what color and flavor you want though. The bulbs develop in response to the amount of light in a day. To help you grow onions that will respond to your regions, they are categorized as long-day, intermediate-day, and short-day types. When selecting a bulbing variety, make sure your selection matches your day-length region.

Long-day:This category is for those who are growing between 37-47 degrees latitude. These onions will develop bulbs with 14-16 hour days and are suited for zones below 6. This is great because many of the long-day varieties can be stored for several months, allowing you to use them throughout the winter. Plant in the early spring.
Intermediate-day:These onions are grown between 32-42 degrees latitude and bridge the gap between the long-day and short-day categories. Bulbs will form with 12-14 hours of light. These varieties tend to be sweet and are ideal for growing in zones 5-6, although many are quite versatile and able to be grown in many zones. May be planted in the winter (warm climates) to spring (northern regions) months.
Short-day:These bulbing onions grow in the southernmost climates of the U.S. between 25 to 35 degrees latitude and need 10-12 hours of light. Expect to grow these in zone 7 and up. Plant in the fall for spring to early summer harvest.

Bulbing Onion Flavors

In addition to day length, the color of your bulbing onions will also greatly affect the flavor you experience. Yellow onions are known for being the best multi-purpose cooking onion. These are the hardiest but also have a pungent flavor that mellows with cooking. Yellows are the best option for long-term storage. These are also difficult to eat raw due to their spicy flavor. White onions are sharp, crisp, and good for cooking or eating raw. Try one in your homemade salsa for a delightful crunch, or use in place of a yellow variety for cooking. Sweet onions share qualities with both the white and yellow types. They are sweet, not pungent, and don’t store well. Use these varieties for the best homemade onion rings. Red onions pack a spicy and pungent burst of flavor that is best eaten raw. During the summer months, red onions may taste slightly milder.

Growing Bulbing Onions

• Seed Depth: 0.25 inches
• Seed Spacing: 3-6 inches
• Row Spacing: 12-15 inches
• Days to Germination: 7-10
• Germination Temperature: 66-70 F
• Soil Preference: Sandy, loose, composted, and well-draining.
• Start Indoors: Yes, 8-10 weeks before frost. May also be directly sown.
• Watering: When watering, try to stay close to the soil level. Keeping water off the foliage will help prevent diseases and encourage healthy growth.
• Harvesting: When the leafy tops fall over you will know your onions are ready for harvesting. Pull the entire plant up with the leaves intact. Be sure to cure your harvest.
• Curing: After harvesting it is important that your onions properly dry. Lay your onions out to dry in an area that is open to air movement. Prevent sunburn by overlapping the foliage over the bulbs. When the neck and outside are dry, cut the foliage off leaving about an inch at the end of your bulbs.

Bunching Onions - Allium fistulosum

Bunching Onions are also known as green onions and are used widely around the world. While they are perennials, they are grown as annuals for their tender green and white stalks that do not develop a bulb. These may be referenced as day-neutral onions. A few varieties will even show a splash of red coloration. Unlike bulbing onions, most varieties will only provide a mild oniony flavor and can be used cooked or raw. Sow your seeds in the early spring for a summer harvest. Some varieties also do well when sown in the late summer for a fall or spring harvest.