Onions, specifically the bulb type for this article, is part of the Allium family which includes leeks, garlic, and chives. Onions have been around for thousands of years. Researchers believe onions have been consumed for a lot longer than that, the official historical record says onions have been consumed for 5000 years. Onions are such a crucial plant that is used for all kinds of applications it’s hard to pin down a better number. Believed to have originated in Central Asia and consumed by ancient peoples from the Samaritans, Romans, and Chinese. Onions have been used to prevent scurvy, earache, and stomach ailments. Ancient athletes used to rub onions on themselves for better muscle tone or consume a few onions before an event for better performance. This article is focused on garden onions or bulb onions. Onions were a crucial veggie used in wars, and as currency, given to ancient laborers because it is a cheap food source. Onions are tough, versatile, biennial usually sown in the spring for a summer harvest. Like many other plants onions have been grown, traded and transported all over the world for good reason, possibly since prehistorical times.

Plant and Go

Dep: ¼ -1/8   space: 4-6in  Row: 12 in Temp: 60-75 Row: 12-18 Germ: 10-20 Sun: Full pH: 6.0-6.8 Harv: 100-120 Soil: Loose, well drained Con:. 24x10 Fert: 5-10-10 Fert Freq: 2-3wks  Water: 1 in Mature Dimen: 16-24. Sow: winter/spring  Name: Allium capa


Companion plant: Brussel Sprouts


Growing onions from seed opens a wide variety of shapes, flavors, sizes, and colors in your home and garden. Bulb onions are photo thermoperiodic which means they are sensitive to day length and daylight hours a onion is stimulated into stopping the productions of the green leaves and starting the production of the bulb as the days start to lengthen, in between spring and summer.  First things first, what zone are you growing in? Make sure to do your research and pick a variety that suits your growing condition or be able to replicate what each onion needs to grow a bulb.


Here are the 3 main categories to choose from:

Short-day onions are ideal for the hardiness Zone 7 and warmer. Short-day onions are typically planted in the fall and harvested in spring. These onions are triggered to bulb when the day length increases to 10 to 12 hours. They can also grow in zones 5 and 6 if planted in late winter instead of fall. 

Varieties include Gabriella, Red Burgundy, Red Creole, and Vidalia.

Day-neutral or intermediate-day onions can grow in almost all regions and are prompted to bulb when the daylight length increases to 12 to 14 hours. They are ideal for gardeners in zones 5 and 6. They can be planted in fall in mild climates and early spring in colder regions. Seeds can be planted in fall for a spring harvest, or in early spring for a mid-late summer harvest.

Varieties include Candy, Red Long of Tropea, and Monastrell, while Cabernet, Calibra, and Red Long of Florance varieties also last a while in storage.

Long-day onions are usually grown in the North regions, hardiness Zone 6 to 3 and colder. It’s recommended they are sown early under lights and transplanted to the garden in spring, so they have plenty of time to grow before forming bulbs. Long-day onions are triggered to bulb when the day length increases to 14 to 16 hours.

Common long-day onion varieties include the following: Ailsa Craig, Bridger, New York Early, and Walla Walla Sweet. Long-day storage varieties that last up to 6 months when stored in a cool area include Cortland, Patterson, PowellRed Carpet, Redwing, Rossa di Milano, and Yankee.

Onions take 90 to 110 days to maturity. There are a few options when growing onions seeds, sets and transplants. Depending on variety and zone, consider starting your seeds indoors under grow lights. Then transplant hardened off seedlings to the garden as soon as the ground can be worked. This gives the plants time to establish healthy roots for optimal growth before the day length increases and triggers the bulbs to form. If you live in warmer regions, planting onion seeds in late summer to early fall, allowing them to overwinter, and make for robust growth when the weather warms.

Sow or sprinkle the seeds evenly as possible, its not that serious you can thin later. Sow indoors or outside based on your grow area. Sow 1/8-inch deep, space goal is 6 inches once established and rows of about 12 inches apart. Pick a location that receives full sun or at least six hours of direct sunlight daily. Onions grow best in loose, fertile soil that drains well. Remove weeds and amend the soil with finished compost to add nutrients and organic material to aid with drainage, and work in an all-purpose organic fertilizer into the soil.

If starting indoor then when onion greens are 5–6 inches tall, it's time to transplant them into individual cells. Transplant seedlings 3 to 4 inches apart depending on the variety, once the ground is workable, and last frost has passed. Once seedlings are transplanted, water. Onions have a shallow root system and need to be watered frequently to keep the soil evenly moist about 1 inch a week. Watch your weather for freezing temperatures. While onions are cold hardy, and can withstand cool temperatures, the young seedlings are vulnerable to frosts and freezes. 

If direct sowing, then plant seeds after last frost. After seedlings emerge, thin them to 3–6 inches apart, depending on the variety. Trim the tips of the greens down to 3–4 inches when they reach 5–6 inches or taller. This encourages thickening, stronger root development, and prevents them from flopping over. Onions can be harvested as young as green onions or left to mature fully. Onions are finished growing when the tops flop over. Stop watering at this point and wait for a dry day to harvest.



Onions are heavy feeders, they need nitrogen to grow green leaves, the more leaves the bigger the bulb. In the beginning you’ll want to feed your onions every two weeks for the first few months with a 10-20-10 fertilizer. Once you see the bulb develop then it’s time to stop fertilizing. Too much or continuing fertilizing can cause the bulb to split or the plant to bolt. Onions are ready to harvest when the tops start to brown and fall over. Depending on the variety, this can take anywhere from 80 to 120 days.

Fun Fact

The Big Onion: Before its skyscrapers dominated the skyline, New York City was nicknamed the "Big Onion" in the 19th century due to its bustling onion trade. 

There are over 700 varieties of onions worldwide, each with its own unique flavor and color. From sweet Vidalias to fiery shallots, the options are endless.

The largest onion ever grown weighed a whopping 18 pounds!


Companion planting your onions with carrots, lettuce, or spinach to deter pests and attract beneficial insects.


Onions can be tricky to start so research is required when choosing the right seed for your zone. Once established onions take care of themselves and don’t require much attention until its time to harvest. Onions can be grown in a container or garden.

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