Planting Onions in the Fall: The Ultimate How-To Guide

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Last Updated on 2 months by Michelle

Growing your own onions is a great way to save money on groceries and have a steady supply of fresh, sweet onions all year long. It’s really easy to do – you can even do it in the fall and winter in warmer climates!

You’ll love being able to grow your own sweet, delicious onions right in your backyard. Not only are they tasty, but homegrown onions are also healthier than store-bought ones. Plus, you’ll know exactly where they came from and how they were grown.

Read on to learn more about how to grow your own onions for 5 cents per onion. This post is all about growing onions in the fall.

Why plant onions in the fall?

Planting onions in the fall can be a great way to get the most out of your garden space.

Planting onions from seed in fall means that you are using your garden space during a time it would otherwise be empty, so you are growing more food per square foot from your garden.

Planting onions also has the benefit of providing you with a fresh crop of onions to harvest in the spring.

Who can plant onions in the fall?

For those interested in planting onions in the fall, it is important to know that not every zone can support this activity.

In order for onions to successfully grow from seed during the fall, the winter months must be warm enough. This is typically only the case in zones 7b and higher if you want to overwinter without using row cover.

However, I have read about people as far north as New York successfully growing onions overwinter, so it’s worth trying if you’re interested.

In these areas, onions can be planted in late September-November and will overwinter for a spring harvest.

For those in very cold climates, it is best to wait until spring to plant onions from seed or sets.

No matter what your climate, with a little planning you can enjoy fresh onions from your own garden.

Which month is best to plant onions in the fall?

There may be other ways to do this, but I’m speaking from my own experience here.

I start my onions seeds in mid-August so they are big enough to transplant out into the garden by the beginning of October.

The transplants need to have enough time to grow and build a strong root system for the plants before they face their first freeze.

In my area, the first frost comes around November 5-November 12, so I make sure my plants have been in the ground AT LEAST 6 weeks before that.

What are the benefits of planting onions in the fall?

There are many advantages you get when you plant fall onions. Once you plant fall onions, overwinter them, and harvest onions in the spring, you’ll always have a bed or two of onions in the

You get big sweet onions early

The biggest benefit I see is that I get big, juicy, sweet onions in April and May, several months before my other spring-planted onions will be ready to eat.

This gives me an advantage over other market gardeners because I have onions to sell at my farmstand when there are no other fresh onions anywhere else.

The least expensive best tasting onions you'll ever have

It also gives me fresh delicious onions to eat at home at a fraction of what I would pay at the store.

The onions you grow from seed will cost about 4 cents each, including fertilizer, other soil amendments, and everything else you spend to grow them. You can’t get cheaper onions anywhere, and if you could, they wouldn’t taste anywhere near this good.

How to plant onion sets in the fall

Planting onion sets in the fall will require you to start the plants from seed, which is not required in the spring.

When you plant in the spring, you can purchase onion sets from many places; your local big box retailer or a company like Dixondale Farms, for example.

You have so many options in the spring, but in fall you don’t have those options. You’ll have to grow these babies yourself!

But don’t worry; onions are one of the easiest plants to grow.

Equipment you'll need

You don’t need much to grow onions. If you have a tray, soil, onion seeds, and water, you’re off to the races.

Large tray with no holes

You’ll need a large tray without holes to plant your seeds in. This will be the same container you’ll grow your onions in until you transplant them out.

Onions seeds

You’ll need a specific type of onion seeds to overwinter them. Short-day onions will give you the best results here.

Why?

Because a short-day onion only needs a shorter day length to start growing a bulb, around 10-11 hours. This is exactly the amount of daylight you’ll get in the south beginning in late February and continuing through April.

If you choose a long day onion variety or even an intermediate day onion variety, the day length won’t be long enough in the spring for the onion to trigger the bulbing process.

If you’re worried that you’ll pick the wrong onion seeds, just buy these exact short-day onion varieties and you’ll be just fine:

Soil

Use a seed starting mix that I recommend like Purple Cow Organics (check here for current price).

This mix is great because it is light enough for the seeds to break through the surface when sprouting, and the mix doesn’t have big chunks of sticks or other matter.

Planting Onions in the Fall: The Ultimate How-To Guide

Planting the onion seeds

This is the easiest part. You literally broadcast the seeds over the soil surface and cover with 1/4-1/2 inch of soil. Press the soil down a bit to make sure the seeds are touching the soil, and water.

Water every few days as needed, or as you see the seed starting mix begin to dry out. You’ll see seeds begin to sprout in about a week.

Grow lights

The seeds will need consistent light for the 6-8 weeks you grow them in the tray. You don’t need anything fancy.

There are several inexpensive grow lights that you can choose from that you can use year after year.

After 6-8 weeks It's time to plant

Step 1 :

Choose a planting site that receives full sun and has well-drained soil. On average, each onion plant will need at least 6 inches of space on either side. I plant my onions 6 inches apart within row, with 4 rows on a 30″ bed. This is pretty intensive spacing, and it works to keep weeds out.

Step 2:

Loosen the soil to a depth of about six inches using a garden fork or tiller. Add Garden-Tone granular organic fertilizer. Then, add a layer of organic matter to the planting bed. this can be in the form of compost, rotted leaves, or well-rotted manure. 

Step 3:

Plant the onion plants. Plant them to a depth where the white part is just covered with soil. Again, I plant my onions in rows at 6 inches apart within the row, with each row about 6 inches from the next row.

How to care for plants after planting

The goal here is to get your plants off to a vigorous start before the cold fall and winter temps slow them down. Make sure they get an inch or so of water each week and weed your beds. That’s all you really need to do at this point.

How to care for your onion plants during their growing season

Around the middle of February, your onions will come out of winter dormancy and start growing!

You’ll want to start an onion fertilizer regimen as soon as you feel temps start to warm up.

Every 2-3 weeks, side dress with a high nitrogen fertilizer like blood meal or alfalfa. Once the onions begin to bulb up, stop fertilizing with nitrogen until they are ready to harvest.

Tips for harvesting your onion crop

Your onions will be ready to harvest when the necks start to soften and fall over where the leaves meet the bulb. Pull only the onions that start falling over until most have fallen. Once most of your onions have fallen over, then pull all of them.

Lay the onions out in a single layer where they can get plenty of airflow around them. A dry shaded space out of the sun is the best place to keep them while they cure.

Keep them there until the tops dry completely. Once that happens, you can cut the dried tops off, trim the roots, and store in a cool dry place with as little lights as possible.

Conclusion

Now that you know how to plant onions in the fall, it’s time to get started! This guide provides all the information you need to have a successful onion harvest. Make sure to follow these simple steps for best results. Happy planting!

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