Onions are a root vegetable that goes well in so many dishes. It is one of the most popular vegetables at every market and produces stands late in the summer and in the fall after the harvest season. This is why growing your onions at home has taken off for a number of gardeners everywhere.
There are several ways to grow onions, but many gardeners find that growing onions from seed to be the easiest and most successful method.
Why grow onions from seeds instead of transplants or sets?
I always prefer to use seeds when I can. Not only are seeds cheaper, but you’ll get more bang for your buck.
When you choose to grow your onions from seeds, you are able to get more plants and ultimately a better harvest than from sets or transplants. With onion seeds, you are able to manipulate the type of onion you want and even getting unique varieties.
Seeds can also store very well when planting, allowing you to grow what you need and plant the rest later, if necessary. Seeds make it easier to do succession planting so that you can harvest over and over again if you’d like.
Are onions hard to grow from seed?
Many people get intimidated with growing plants from seed. If you’re not sure where to start with seeds, then you may want to read about when and how to start seeds at home.
Growing onions from seed is not hard to do. Like other root vegetables, they need a healthy dose of soil in a seed tray, sunlight, and lots of water.
The thing to remember about growing onions from seeds is that it is not a hard process, but it is a time-consuming process. It is a slower grow than the other options, but the results are worth it when it is time to harvest. If you’ve planted a fast-growing crop, like lettuce, you may have unrealistic expectations for your onion crop.
Make sure that you’re giving your onions plenty of time to grow.
Choosing the Type of Onion
When you get the seeds for your onions and begin to plant, it is important to know what kind of onion you want. There are several options to choose from when it comes to onions based on their use and taste.
Another important factor to consider is the time of the year that you’ll be planting them. Onions are identified not just by color but by the hours of daylight they need in order to grow efficiently. Some onion varieties require more hours of daylight than others, so you’ll want to choose the type of onion best suited for when you’ll be growing.
True to their name, short-day onions start developing bulbs as the days transition from short to long, around 10-12 hours a day.
These onions often are sweeter than other varieties and are used most frequently in cooking a variety of dishes. They have a higher sugar water content than others, which makes them naturally sweeter.
They are also popular options found in the Southern states, where milder winters and much warmer days are more frequent.
Some of the short-day onion varieties include the following:
- White Bermuda Onions
- Gabriella Onions
- Cippolini Red Onions
- Hybrid Yellow Granex Onions
- Texas Supersweet Onions
- Georgian Vidalia Onions
Intermediate-Day Onions (AKA Day-Neutral)
The most versatile and flexible onion options are intermediate-day onions or day-neutral onion varieties.
The beauty of these onions is the fact that they can be grown anywhere. Like the long-day options below, they are easy for storage and give farmers across the states options.
They also have a sweeter taste to them like the short-day onions, but can be grown up North to give a taste variety to those living in these areas.
These are some of the common day-neutral varieties:
- Super Star Onions
- Candy Onions
- Red Candy Onions
With a requirement of 14-16 hours of sunlight, long-day onions thrive more in the Northern regions of America.
They have a much lower sugar water content than others and have a higher sulfur content. These onions won’t be as sweet, but they’ll have a stronger ‘onion’ flavor.
They have the ability to store for longer periods, making them ideal for long winters.
This is the onion variety for you if you live north of the Mason-Dixon line. If these onions are planted in the Southern region, they may not have a chance for their bulb to properly develop.
Another interesting note about long-day onions: their bulbs also seem to be larger compared to short-day onions.
Popular long-day onions include:
- Blush Onions
- Copra Onions
- Walla Walla Onions
- Ringmaster Onions
Still not sure which type of onion to plant? Watch the video below to understand onion varieties based on location:
What is the best month to plant onions?
If you live in the Northern region, your onions need to be planted in the early spring so that they start taking advantage of the longer days. Most onions are planted by early April. As the next couple of months come, the days will get longer, allowing the onions to grow and the bulbing process to take place.
In the South, onions can pretty much be planted year-round, especially the closer down and to the coast you get.
For those planning to have onions ready in the summer, they need to be planted in early April as well, so that they can begin taking advantage of the 10-12 hours of required sunlight. For a later harvest, you can plant your onions in late September or early October for a Spring harvest.
How to Sow Onion Seeds
If you are looking to grow onions from seeds, then you need to decide the method you want to take and what works best for you. There are two methods for starting onion seeds:
1. Starting Onion Seeds Under Lights
You need to get a seed starter tray filled with a pre-moistened seed starter mix that is full of nutrients.
Dust the top of the soil evenly with the onion seeds before topping them off with a second layer of soil.
Once they are covered, mist with water 2-3 times a day while leaving them under a heated light.
You want to keep the area around 70 degrees, no more than 75, allowing them a comfortable environment to grow.
Once they have started to sprout, you can reduce the temperature by a few degrees until they are planted in the garden.
2. Winter sowing onion seeds (growing under a plastic dome for mini-greenhouse effect)
During the winter sowing process, you follow the same steps when it comes to putting the seeds in the seed starter tray.
However, you add a plastic dome over the seeds, creating a level of humidity and developing that greenhouse effect. If you’re living in a milder climate, you can do this right in your garden bed. The plastic dome will warm the air and soil underneath it when the sun hits it. The dome keeps the warmth from the sunlight trapped, creating a mini ‘greenhouse’ for your onions.
If your winter is especially rough, you’ll want to do this indoors so that the seeds are warm enough to germinate. Remember, 70 degrees is the ideal temperature for the seeds to sprout.
A heat lamp is not required until you remove the dome when the seeds begin sprouting and growing too large for the dome.
Can you direct sow onion seeds?
It is possible to direct sow onion seeds, but it requires more skill and knowledge to plant them properly so that you get a successful harvest.
You’ll want to direct sow them after the threat of frost has passed. Not sure when your last average frost date is? Check here.
Onion seeds will sprout into small, tender shoots at first. These shoots are easily damaged by heavy rain or hail, so you’ll want to take extra precautions to care for them. Once the onions have grown and developed sturdier leaves they will require less care.
How to Harden Off Onion Seedlings
Hardening off seedlings is critical to keeping them alive once you move them outdoors. When seedlings are indoors, they’re not exposed to temperature changes or intense sunlight. If you were to move them straight outdoors from being inside, it may be too much of a shock to them.
You’ll want to get your onion seedlings adapted to life outside gradually with a process called ‘hardening off’. This essentially means getting your onions used to being outdoors gradually.
It is time to harden off your onion seedlings a month before the last expected frost. While onions are able to survive in cooling temperatures, freezing temperatures can damage onion seedlings that are much more vulnerable.
Begin the hardening off process in an area for a few hours at a time, adding a little more over each day. Start by letting your onions be outside in the shade. You can gradually increase the amount of direct sunlight they get.
Spread the hardening off process out over a 2-week period until you’ve worked them up to being outdoors 24/7 and being in direct sunlight all day.
Transplanting Onion Seedlings into the Garden
Before you begin transplanting your seedlings, you need to know which area is right for them.
Select an area that gets at least six hours of sun daily and has loose soil. Hard and compact soil will restrict bulb growth.
Carefully remove these seedlings from the container and separate them at least 4-5 inches from the next plant.
You want to massage them loose from each other if you have multiple onion roots linked together. All you need is to gently pull the soil forward and lay in the root ball.
Pull the soil back and move to the next. Since they thrive in loose soil, no patting is required for onions. Just make sure that your plants are all upright.
How long does it take to grow onions from seed?
If you plan to begin growing onions from seed, plan to invest at least five months from the initial sowing to the harvest of the onions.
They need time to sprout and then begin the bulbing process as the weather changes. This is true whether you’re growing short-day, long-day or intermediate varieties.
Growing Onions from Seeds: Potential Problems
While the options and varieties are great with seeds, there are some potential problems with growing onions from seeds.
Because the weather could often change, the issue of bolting in the root system can develop and adversely impact the growing onions.
Bolting occurs when temperatures cause the plant to produce flowers and reproductive parts. A bolted plant tastes bad and often has an off texture. If your onion bolts, the best thing to do is to let it bolt, flower, and then collect seeds from it and try again.
Also, as they continue to grow from seedlings, they are more vulnerable than sets or transplants that have been exposed to different weather options. Onion seedlings are small and very tender, which makes them vulnerable to damage from hard rain or hail.
Bulbs Not Developing
Onions that are planted too close together will not be able to develop a nice-sized bulb. Make sure that the soil is loose and that neighboring plants are spaced at least 4-5″ away.
You’ll also want to make sure that you’re feeding the onions enough. Your soil should be rich in nutrients. If it’s not, add fertilizer to feed the developing onions. Choose a fertilizer with higher amounts of nitrogen and phosphorus to promote healthy root and bulb development.
If the soil isn’t quite right, your onions may turn yellow. White onions that are yellow when you harvest them could be from soil that doesn’t have enough nutrients. Yellowing can also be caused by improper soil pH.
Several yellowed onions should be a sign that you either need to fertilize more or that you need to test your soil. A rich soil that has a ton of nutrients can’t provide those nutrients to the plant if the soil’s pH is outside of the plant’s ideal range. Have your soil tested for pH and amend the soil to get the pH back into the range.
Growing Onions From Seeds
Don’t be intimidated by growing onions from seeds. Growing onions from seeds is a much more reliable method than growing onions from sets or transplants. I’ve planted onions numerous times from sets and was only able to harvest a handful of onions. When I’ve started them from seeds, I’ve been much more successful.
You’ll be able to choose from different varieties, whether you want a sweet onion or a nice purple onion, or an onion that will grow well in your area. No matter what type of onion you want to grow, you’ll be able to find it easily in a seed.
Make sure that you’re choosing the right type of onion for where you live. Do you need short-day onions that are suited for growing in the Southern states or do you need long-day onions that are better suited for growing in the Northern states?
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How do you grow onions from seed? What’s your favorite type of onion to grow from seed? Let me know below!