How to Plant, Grow, and Harvest Onions

Knowing how to grow onions well and have them store for up to 9 months feels like a rite of passage for homesteaders, doesn’t it? There’s definitely an art to it, but once you crack the code, you feel like you want to shout it to the rooftops. Plus, if you’re wanting to live a more self-sufficient lifestyle, having long-storing produce like this truly is invaluable.

However, growing onions can be confusing. Should you grow long-day onions or short-day onions? Should you direct seed, start plants indoors, or buy sets? What variety stores the best? WHEW!.

I’ve been growing onions for 15 years and have been through it ALL. Good years. Bad years. Bolting. You name it. We’re going to break down everything I know about them, and by the end of this article, you’ll be armed with lots of knowledge and know exactly what to do to grow fantastic onions!

*Disclosure: This post may contain affiliate links to products (including Amazon). I’ll earn a small commission if you make a purchase through my link, at no additional cost to you! Regardless, I only link to products that I personally use on our homestead or believe in.

What Kind of Onions Should You Grow?

Before jumping straight into how to grow onions, it’s important that you pick the right kind of onion for your location and your personal goals. Not all onions are created equal!

Long-Day vs Short-Day Varieties

Onions are the only vegetable out there (that I’m aware of) that have different light requirements in order to set good bulbs. Be sure the pick the right variety based on where you live:

Long-day onions: If you live north of the Kansas/Oklahoma border
Short-day onions: If you live south of the Kansas/Oklahoma border
Intermediate day onions: These grow anywhere!

Storage

Another thing to consider is whether that variety stores well or not. If you’re only wanting fresh eating onions during the summer months, then anything will do. The Walla Walla onion is a common fresh-eating onion that doesn’t store very well.

There’s nothing more disappointing than carefully braiding your onions, packing them away in storage, only to have them sprout in a couple of months. If you want to become more self-sufficient and store onions all winter, be sure to pick a variety that is known to store well; I love Sedona F1!

The Homesteading RD's Product Picks
	Sedona F1 Onion Seeds I absolutely LOVE growing these onions and I've been using them for years! They are hardy, easy to grown, and delicious. Plus, they store super well! Shop at High Mowing Seeds

Onion Seeds vs Onion Plants vs Onion Sets

Now that you know what variety is best for you and your location, it’s time to select how you want to go about planting those onions. There are 3 main routes you can go: seeds, sets, and plants. All of them come with their own pros and cons!

Onion Seeds

Direct sowing onions is the simplest method and usually results in better onions, too! They are less susceptible to stress, bolting, and disease, while also storing better. The catch is that onions need a LONG time to mature, so this is only a viable option for those in warm climates with a long growing season.

*Onion seeds are only viable for 1 year, so be sure to get new seeds every year!

Onion Plants

For those of us who live in the north, utilizing onion plants is a better route to ensure success. Onions need a long time to mature. They are one of the first seeds that I start indoors – a full 12 weeks before they go outdoors, which ends up being late February for me.

They can be a little tricky to start from seed, so here’s my best tips:

Use a good-quality seed starting mix
Seed them thickly (20 seeds per 2.5″ pot) – I love the 4-Cell Seed Starting Trays (*use my code THRD5 for 5% off!)
Ensure that your pots are deep to allow for good root development
Use a seedling heat mat for germination
Use a high-quality grow light to encourage strong growth
Once the onions are 4-5″ tall or starting to droop, give them a haircut back to about 3″ tall. Continue to trim them until planting time. This aids in root growth.

Watch me start my onions here!

Onion Sets

If you don’t have time to babysit your onions indoors for 3 months, I get it! It’s not for everyone. Onion sets are a tempting option because they are small onions (usually dime size) that were grown the previous year and then held in dormancy until they can be planted again.

The thought is that you can plant them and they’ll pick up where they left off, and since there’s a small bulb already, you’ll feel like you have a head start! The catch is that they often don’t develop very big bulbs, they don’t store as well, and they are prone to bolting.

I’d recommend buying onion plants from your local nursery and using onion sets only as a last resort!

How to Plant Onions

Now that you have your seeds, sets, or plants in hand, it’s time to chat about how to plant them so that you have an excellent harvest in a few months. Onions are fairly hardy, but they do require some specific care to keep them happy.

Location

Onions LOVE and need a lot of sunshine, so be sure to plant them in a full-sun location. Save those shady spots for those plants and herbs that tolerate shade.

Prepare the soil

Since onions have very shallow root systems, the soil must be fertile and loose. Sandy loam is ideal! Compact, heavy, wet clay is not your friend when it comes to growing onions.

As someone who naturally has rocky clay soil, it’s been a challenge, but it’s certainly possible! Adding compost each fall and loosening up the soil with a broadfork (my code “THRD5” gets you 5% off!) and garden claw has helped tremendously.

Choose the right time.

It’s important to plant at the correct time of year and to pick a good weather window. If you plant too soon, your seeds could rot in the ground, or they may bolt (if using plants), but if you plant too late, they may fry in the heat before they get established.

Seeds: Direct seed when the soil temperature reaches 50°F – get a soil thermometer if you don’t have one already!
Plants: Transplant onion seedlings outdoors after your last frost date. Some sources say you can transplant them out 2-4 weeks before your last frost date, but I like to play it safe. It’s up to you!
Sets: Plant onion sets after your last frost date.

Plant spacing and depth

Onions can tolerate fairly dense planting thanks to their small root system, but they still like a little elbow room so that they don’t have to compete too hard for those precious nutrients.

Seeds: Place seeds 1/4″ deep, 1/2″ apart and in rows 6″ apart. Thin to 4″ apart, removing the weakest ones.
Plants: Gently tease the seedlings apart and space them 4″ apart in rows 6″ apart. You can make a shallow trench or plant each one individually. I like to use a cardboard spacer to make planting a breeze (see photo below). Pick the strongest ones for planting. Gently press them into place.
Sets: Plant sets 3-4″ apart in rows 6″ apart and deep enough so that their pointed tops are even with the top of the soil. Pick bulbs that are about the size of a dime, as they are less likely to bolt compared to larger ones.

How to Grow Onions

Regular weeding is a must-do task since onions don’t like competition. Weeding tools can be a little aggressive on their delicate root systems, so it’s best to pull weeds by hand and regularly. I know it’s a pain, but it’s well worth the effort.

Onions have very shallow root systems, so they need regular watering. The first week after planting is the most crucial time and may require daily watering, depending on your climate and soil structure. Be sure to water anytime the top inch of soil dries out.

Since both of these tasks can be labor-intensive, I like to mulch my onions with organic straw. This reduces the weed pressure and aids in moisture retention in my soil. A win-win all around!

Thankfully, onions don’t need much when it comes to nutrients, so regular fertilizing usually isn’t necessary, unlike heavy feeders such as corn, tomatoes, and squash. In fact, too much nitrogen can result in lots of greens, but small bulbs. As long as your soil is optimized and the onions are growing well, just let them do their thing!

How to Harvest Onions

Thankfully, it’s pretty easy to tell when onions are ready to harvest (unlike butternut squash – that one’s a little tricky!). All you need to do is keep an eye out for when the green tops start to fall over, depending on where you live:

Cool, humid locations: Harvest when almost all of the tops fall over
Cool, dry locations: Harvest when half the tops fall over
Warm locations: Harvest when ¼-⅓ of the tops fall over

Onions have shallow root systems, so they pull up easily, unlike garlic, which grows fairly deep. Grip an onion at the base where the greens meet the bulb and give it a firm tug. Easy peasy!

How to Cure Onions

Onions can be stored for a long time if you cure them properly. We are often eating “fresh” onions for up to 9 months, so they are a big part of our self-sufficiency strategy. It’s definitely worth the effort!

Onion curing is a matter of debate in the gardening world. Some people swear by curing in the sun, while others say it should only be done indoors with a fan. I personally like to cure in the sun, but I also live in Minnesota, where the sun isn’t too intense.

My favorite method is just to pile them all in a wagon – it’s easy, has good airflow, and I can wheel it indoors anytime it rains. When I first started gardening and had smaller harvests, I used an old screen door that I found at a garage sale to lay them on. I’ve seen other people use racking systems. You can get creative here!

Whichever method you decide to use, just be sure that there’s good airflow and that you give them a full 1-2 weeks to fully cure, depending on your environment.

You’ll know that they are ready for storage when the green tops and protective papery skins surrounding the bulbs are dry. Trim the root hairs to ¼” long once curing is complete.

How to Store Onions

There are two main ways that you can store onions. The first is to pile them in a crate with lots of holes for ventilation, or hang them in a mesh bag. The second (which is my favorite) is braiding.

Braiding allows for great airflow (reducing the risk of them rotting or getting moldy), and they are easy to hang for storage. No need for storage bins! Plus, they look so beautiful, don’t they?

*Just be sure to braid them before the green tops completely get dry out and crumbly, otherwise they’ll fall apart during the braiding process.

No matter which way you choose, just be sure that they get good airflow (don’t put them in a cardboard box). Find a spot that’s cool and dark, but above freezing. A basement, root cellar, or heated garage works best.

Bonus points if you store them away from apples and tomatoes. They give off ethylene gas, which can cause onions to sprout prematurely.

How to Plant, Grow, and Harvest Onions