How to Grow Onions From Seed: A Beginner’s Guide

How to Grow Onions From Seed?

To grow onions from seed, start by selecting the appropriate variety based on your climate and desired harvest time.

Short-day onions are suitable for warmer regions, while long-day onions are grown in cooler climates.

Start the seeds indoors 8-10 weeks before the last frost date.

Use recycled berry containers with good drainage filled with seed starting mix.

Sprinkle the seeds on top, cover with a shallow layer of soil, and press gently.

Keep the containers in a warm area until the seeds sprout.

Then, move them under lights in a cool location and water regularly using diluted fish emulsion or compost tea.

Trim the tops of the seedlings to prevent top heaviness and promote root growth.

Harden off the seedlings before transplanting them to a sunny location with well-draining soil.

Keep the bed weeded and water the onions frequently until they are ready for harvest.

After harvest, lay out the onions to cure and store them for winter.

Key Points:

  • Select appropriate onion variety based on climate and desired harvest time
  • Start seeds indoors 8-10 weeks before last frost date
  • Use recycled berry containers with good drainage and seed starting mix
  • Sprinkle seeds on top, cover with shallow layer of soil, and press gently
  • Keep containers in warm area until seeds sprout, then move under lights in cool location
  • Water regularly with diluted fish emulsion or compost tea and trim tops of seedlings for root growth


Did You Know?

1. Onions were cultivated as early as 5,000 years ago in ancient Egypt, making them one of the oldest known vegetables to be grown from seed.
2. The onion is a member of the Allium family, which also includes garlic, leeks, and chives. This family is known for its pungent aroma and medicinal properties.
3. Onions have been used for various purposes throughout history, including warding off evil spirits, paying tribute to gods, and even being used as currency by the ancient Egyptians.
4. The world’s largest onion, weighing in at an astonishing 18 pounds and 11 ounces, was grown by Peter Glazebrook in the United Kingdom in 2011.
5. Onions can have different flavors depending on the soil they are grown in. For example, onions grown in sulfur-rich soil tend to have a stronger taste, while those grown in milder conditions have a more delicate flavor.

Growing Onions From Seed: A Variety Of Shapes, Flavors, Sizes, And Colors

Growing onions from seed offers a vast array of options when it comes to shapes, flavors, sizes, and colors. Unlike purchasing transplants or sets, starting from seed allows you to choose from a wide variety of onion varieties, each with its own unique characteristics.

Onions come in different shapes, ranging from round to flat, and even torpedo-shaped. The flavors of onions can vary from mild and sweet to pungent and spicy. You can also find onions in various sizes, from small pearl onions to large bulbs. Lastly, onions are available in an assortment of colors, including white, yellow, red, and even purple.

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When selecting onion seeds, it’s important to choose ones that will be used within one or two years. Onion seeds have a limited shelf life, and their viability tends to decrease over time. Additionally, if you’re planning to store onions for winter use, make sure to choose onion varieties that are known for their long-term storage capabilities.

Options For Planting Onions: Transplants, Sets, Or Seed

There are several options for planting onions: transplants, sets, or starting from seed.

Transplants are young onion plants that have been grown from seed and are ready for transplanting into the garden. You can purchase onion transplants online or at local garden centers.

On the other hand, onion sets are small, immature bulbs that have been grown the previous year and are planted directly into the ground.

While transplants and sets offer convenience, growing onions from seed provides the most diversity and control over the final outcome. It allows you to choose from a wider array of onion varieties and ensures that you have the freshest onions possible.

However, it’s worth noting that growing onions from sets may not yield good results in terms of sprouting and bulb size, as they are often compromised due to their age and storage conditions.

Tips For Starting Onions Indoors: Lights, Timing, And Containers

To start onions from seed, it is best to begin indoors 8-10 weeks before the last frost date. This timing allows the seedlings to establish themselves before being transplanted into the garden.

You can use recycled berry containers with good drainage to grow onion seedlings. Fill these containers with pre-moistened seed starting mix, sprinkle the onion seeds on top, cover with a shallow layer of soil, and press gently to ensure good seed-to-soil contact.

Label the containers and place them in a seed flat or waterproof container. Cover them with a humidity dome and put them in a warm area with a temperature of around 70-75°F (21-24°C). This warm environment will help the seeds germinate successfully. Once the seeds sprout, remove the humidity dome and place the containers under lights in a cool location.

It’s important to keep the soil evenly moist and water the seedlings with diluted fish emulsion or compost tea every two weeks to provide necessary nutrients.

To prevent the containers from becoming top-heavy and to provide more nutrients to the roots, trim the tops of the onion seedlings to around 3 inches high. This practice promotes a more robust root system.

Approximately four weeks before the last expected frost date, the seedlings should be hardened off to adapt them to outdoor conditions.

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Transplanting Onion Seedlings: Sunlight, Soil, And Fertilizer

When transplanting onion seedlings, choose a sunny location that receives at least six hours of direct sunlight per day. Onions thrive in full sun and require this exposure to develop properly. The soil should be well-draining and fertile, so it’s essential to work in an all-purpose organic fertilizer, such as Espoma Plant Tone, before planting. This aids in providing the necessary nutrients for healthy onion growth.

Carefully remove the seedlings from the containers by gently squeezing the plastic, turning the container upside down, and shaking gently. Be cautious, as the root ball of the onions may break apart when removed from the container. To prevent the roots from drying out, gently tease the onion seedlings apart for planting one at a time.

Space the separated seedlings 3 to 4 inches apart, depending on the variety. Proper spacing allows the onions to grow and expand without overcrowding each other. After transplanting, gently water the bed to ensure that the shallow root system of the onions remains evenly moist. Frequent watering may be required to achieve this.

  • Choose a sunny location with at least six hours of direct sunlight per day.
  • Ensure the soil is well-draining and fertile by using an all-purpose organic fertilizer.
  • Carefully remove the seedlings from containers to prevent root damage.
  • Space the seedlings 3 to 4 inches apart to allow for proper growth and expansion.
  • Gently water the bed after transplanting to keep the shallow root system evenly moist.

Caring For Onions: Watering, Weeding, And Harvesting

Caring for onions involves regular watering, weeding, and proper harvesting techniques. Onions have a shallow root system, so it’s crucial to keep the soil evenly moist. Watering deeply and frequently prevents the onions from drying out and promotes healthy growth. Ideally, provide around 1 inch of water per week, either through rainfall or irrigation.

Weeding is essential to prevent competition for nutrients and resources. Keep the onion bed weed-free to ensure that the onions receive the necessary nutrients without any hindrance.

Onions can be harvested at various stages of maturity. If you prefer green onions, you can harvest them when they are young and tender. However, if you want fully mature onions, wait until the tops flop over. This indicates that the onions are ready for harvest. At this point, stop watering the plants and wait for a dry day to harvest.

Storing Onions For Winter: Curing And Drying Techniques

After harvest, curing the onions is crucial for winter storage. Curing involves drying the onions in a well-ventilated area for a few weeks to toughen their outer layers and extend their shelf life.

Here are the steps for proper curing and storage:

  1. Lay the harvested onions in a single layer, ensuring that they don’t touch each other. This allows for optimal airflow and prevents moisture buildup.

  2. To speed up the drying process, you can brush away soil from the bulbs. This helps them dry faster. Additionally, exposing the tops and bulbs by pulling away soil also aids in the drying process.

  3. Once the onions are properly cured, store them in a cool, dry, and dark place. Ideal storage conditions involve temperatures between 32°F and 40°F (0°C and 4°C) with a relative humidity of 60-70%.

  4. Regularly check the stored onions for any signs of spoilage or rot. Discard any affected bulbs to prevent the spread of spoilage.

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Remember, proper curing and storage techniques are essential for maximizing the shelf life of your onions.

Frequently Asked Questions

How long do onions take to grow from seed?

Onions typically take approximately 90-100 days to fully mature when grown from seed. This process typically spans over four months, providing ample time for the onions to develop. However, if utilizing sets instead, the maturity period is slightly shorter, with onions being ready for harvest in around 80 days, or just under three months. Whether grown from seed or sets, the growth period of onions demands patience and dedication to ensure a successful harvest.

Can onions be grown in pots?

Yes, onions can indeed be grown in pots. The size of the pot depends on the type of onion you want to grow. For scallions or spring green onions, an 8-inch pot or larger is suitable. However, if you intend to grow bulb onions, it is essential to choose a container that is wide enough to allow each onion to have approximately 3 inches of space around it. By carefully selecting the appropriate container size, you can successfully cultivate onions in pots.

Do onions grow fast?

Onions can be considered relatively fast growers with an average growth rate of 100 to 175 days until maturity. While this might seem like a lengthy timeframe, it’s important to note that different onion varieties have varying growth rates. Some popular varieties like Texas Super Sweet, Vidalia Onions, Yellow Granex, and Southern Belle Red are typically grown in the South and planted in the fall for harvest in the spring. These onions, specifically adapted to the region’s climate, are designed to maximize growth efficiency and produce a bountiful harvest within the given time frame.

How many onions grow from one seed?

When it comes to growing onions from a single seed or set, the outcome remains consistent – one onion. Regardless of whether you opt for seeds or sets, the result will yield a solitary onion. The process of cultivating onions may be uncomplicated, yet it is fascinating to witness how a single seed or set can transform into a healthy, fully-grown onion.

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