How to Grow Onions From Seed


Since onions were initially domesticated and intentionally bred, it has been at least 7,000 years. Without onions, many of our favorite foods wouldn’t be the same; I think we can all agree on that. To add flavor to many meals, onions are a year-round culinary necessity.  The flavor and adaptability of onions are exceptional. You can enjoy onions all winter long because they are easy to grow, have a huge variety, and have a long storage life. In the spring, local garden centers and nurseries often provide onion sets, which are immature bulbs sown the previous year.

There are several ways to cultivate onions, including seeds, transplants, and onion sets. Finding out how to grow onions from seed is one of the best strategies. Onions come in a great range of shapes, flavors, sizes, and colors and can be produced from seeds.

Make sure you plan to use the onion seeds within two years after purchasing them because the longer they sit, the less likely they are to sprout. The onions can either be used as green and scallions as soon as they sprout, or you can wait until they are completely developed and harvest the bulbs. Onions may be grown from seed, and we’ll provide all of our best tips for doing so. If you’ve been looking for information, you’ve come to the right place.

How to Grow Onions From Seed

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Onions take a while to mature from seed. If you live in an area closer to the equator, you can plant onion seeds in the late summer or early fall, let them overwinter, and they will grow when the temperature warms. Select varieties suitable for the area where you will be growing them.

They don’t last very long, so only purchase onion seeds if you plan to use them within a year or two. If you plan to keep onions for the winter, pick varieties that are known for their ability to be kept for a long time.

To produce onions from seeds, follow these instructions:

  • Eight to ten weeks before the last day of frost, the onion seeds should be started indoors. This head start will be advantageous to the seedlings. Thanks to it, they can develop healthy seedlings before being placed outside.
  • Make careful considerations when choosing a container for your seeds. The seeds shouldn’t be sown too tightly.
  • Filling your pots with pre-wetted seed starting mix is recommended. The seed starting mix has to be moist and placed in a shallow container. The container must be around 4 inches deep and include a few drainage holes. Once the containers are full, evenly place the seeds on top of the soil, spritz with water, cover with 1/8-inch of seed starting mix, and gently press down to ensure the seeds are in contact with the moist soil. Add enough potting mix to cover the seeds after generously scattering them around the soil’s surface.
  • Keep the seeds warm and wet until they begin to grow. Place them on a heating pad or somewhere warm between 70- and 75 degrees Fahrenheit, then place them in a seed flat or watertight container. Finally, cover with a humidity dome.
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  • Although it can take up to two weeks for onion seeds to sprout, you can drastically speed up the process by keeping the soil warm.
  • Removing the humidity dome and planting the plants in a cool, well-lit area will cause the seeds to sprout.
  • The soil should be periodically fertilized and kept moist.
  • When the green shoots have grown to about 5 inches, cut them back to 3 inches. By doing this, the containers won’t topple over, and the roots will receive more nutrition than the leaves.
  • When the third leaf emerges, onion seedlings are prepared to be hardened off and planted in the garden. Harden the seedlings for four weeks before moving them outside. During this period, gradually adapt the seedlings to the outside. Start by leaving them out for a short period in a safe location, then bring them inside for the balance of the day. Increase their exposure to the outdoors a little bit each day until you can leave them outside all night. Rows should be spaced 12 to 18 inches apart, with a transplant spacing of 4 to 5 inches.

Types of Onions You Can Grow From Seed

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Choose a seed that is suitable for your development zone. Onions come in three varieties: short-day, day-neutral, and long-day. These classifications are based on your location’s growing zone and plant hardiness. If you choose the wrong variety of onions for your area, you might not have a very productive crop. Using tools and resources available online, you may locate your zone. Consult a chart of the zones for plant hardiness to learn more about your area.

The milder winters and fall enable year-round growth and March, April, and May harvesting in areas with a plant hardiness zone of 7 or higher, where short-day onions flourish. Short-day onions start to the bulb when there is an increase in daylight hours from 10 to 12. If you live in Zone 7 or another warm region, pick short-day onions like Red Burgundy, Red Creole, and Vidalia.

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It is possible to cultivate day-neutral or intermediate-length onions in almost any setting. Day-neutral onions are induced to the bulb when the amount of sunlight is raised to 12 to 14 hours. Any growing zone is suitable for cultivating day-neutral onions like Cabernet and Candy.

In the North, plant hardiness Zone 6 and colder climes are where we grow long-day onions. They are sown under lights early in the year and brought to the garden in the spring to give them plenty of time to mature before turning into bulbs. Long-day onions start to the bulb when there are 14–16 hours of sunshine every day. Those who live in Zone 6 or other cooler climates should choose long-day onions such as Alisa Craig, Copra, and White Sweet Spanish.

How Long Does It Take to Grow Onions From Seed?

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The time it takes for different species of onions to mature from seed to harvest might vary significantly. Usually, it takes 3 to 5 months from the time of seeding till the crop is mature. They are prepared when a flower’s stem appears or when the green tops of the plants begin to turn yellow and wilt.

Despite being excellent in any size, you may always consume some of your crops before it matures. Gently pull the onion bulb from the soil around it if you plan to use it immediately away. Keep your onion in the ground but dig part of the soil away from the bulb’s perimeter so it can be exposed to air and encouraged to dry. Your onion will last longer if you do this. After a few days or when the tops are dry, dig the onions out of the ground.

What Month Do You Plant Onion Seeds?

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Depending on your strategy, you should sow onion seeds at a specified time. The optimum month to plant onion seeds varies depending on where you live and the climate, just as with any other plant. Onions can either be planted in the spring or the fall. Onion seed planting is generally advised to be done 10 to 12 weeks before the last frost date.

For onions planted in the fall to establish roots in the ground, they need at least 4 to 6 weeks of warm weather. The best time to plant onion sets is from the middle of March to the middle of April. Sets may also be sown in the autumn, from late September to early October.

You want to make sure that the weather where you are is cool and not chilly. Since the weather is getting cooler, they will grow tops. You can start planting your onion seeds in the fall or winter if you live somewhere with mild winters. As soon as the temperature rises, they start to grow bulbs.

Onion sets should often be planted outside when the temperature is low but not freezing. Before direct sowing outdoors, hold off until the soil is ready to work in the early spring and the temperature is above 40°F. This typically happens a few weeks before the final frost date in your area. You can put them straight into the garden in the fall or early winter in warmer climates.

Should I Soak My Onion Seeds Before Planting?

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Impatient gardeners might wonder if this step is necessary or if it is just a nice-to-have that won’t matter in the long run. This is because soaking must be done at least a few hours before planting, ideally overnight. We all know that seeds in the wild can sprout on their own without our help. They have evolved over millions of years to reproduce without the attention that household gardeners give them. Before planting, onion sets don’t need to be soaked, yet moist onions sprout more quickly.

It is beneficial to soak onion seeds first before planting. If you soak the sets in compost tea, they’ll get extra nutrition and protection from illness. Some seeds can be sown without soaking but doing so can greatly increase your chances of success and speed up the germination process. If done properly, it can mean the difference between a small percentage of the seeds—say, one or two—germinating or the majority of the batch.

You don’t need to moisten the onions before planting them, though they will sprout more quickly if they do. Seeds can be hydrated and planted in trays or on the ground, and then you need to wait for the first growth indicators.

Can You Put Onion Seeds Straight Into the Ground?

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Onion seeds can be sown outdoors in the ground or indoors in covered pots, which are the two most common methods. The advantages of starting seeds inside as opposed to buying mature plants from a nursery are well known to many gardeners. Although indoor sowing in pots requires the most effort, the resulting unions are larger and mature a few weeks quicker.

However, if you want to plant them right away, you should sow them in the ground in April or May or as soon as the soil can be prepared in the early spring. Plants should be placed 1 1/2 to 2 inches apart for the highest yields in fertile soil.


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Homesteaders are incorporating onions into their backyard gardens at an increasing rate. A vegetable that can be found in all cuisines is the onion. Despite what many people think, onions are among the easiest crops to grow. While growing onion from seed might not always seem the most straightforward option, it is. Undoubtedly, you are capable of handling it alone.

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