Growing onions is a pretty simple garden task. Start growing onions by just following these 7 steps for your best crop ever!
Growing Onions
I have read a million guides for growing onions. In fact, I’ve even writtten some of them. However, all the guides on growing onions are long and complicated.
I have written this article as a quick guide to get you started growing onions this year! Everything you need to know about growing onions in just 7 easy steps.
Step 1 – Choose the proper onion for your region
Did you know some types of onions only grow in certain parts of the country? It’s all based on your latitude and day length. The different day lengths are as follows, long-day onions, intermediate-day onions, or short-day onions.
You need to know which type of day-length onion you can plant in your area so you can decide on the right onion variety to grow in your garden. Which onion day length is best for you?
If you would like to learn more about onion day lengths and what it means for your area here’s a video that I recently did explaining more:
https://youtu.be/MMjO-ilQrvI
Step 2 – Choose Onion seeds, sets, or starts.
Unless you live in southern Florida you will be starting seeds indoors so those seedlings are ready in time to go outside. Onions started from seed need 10 weeks before they are ready to go in the garden.
When you plant onion Sets they are tiny baby onions that you simply poke in the ground and they grow into onions. This is the easiest method to start onions but they seldom grow a large onion bulb from sets.
In my humble opinion starts are the best method for growing onions. This way they get off to an early start and grow the biggest and healthiest bulbs. (This post will teach you more about growing onions from starts)
Step 3 – Planting Onions
When you are planning where to plant onions keep the amount of sunlight the spot gets in mind. Onions grow best in full sun with well-drained soil.
When planting onions forget what you read about spacing. Four inches of space all around is perfect. This allows you to plant a ton of onions in very little space. We put as many as 150 plants in a spot just 4 by 8 feet.
Planting Depth
- Plant by seed-Cover seeds with 1/4 inch of soil
- Onion Sets-Press in soil about an inch deep
- Plant seedlings with root down about 1-2 inches below soil
- Green Onions- Plant deeper and closer together about 3 inches deep
You can also plant your onions much earlier than you think. We often have ours in the garden the last week of March. Onions are super hardy and don’t mind frost at all when they are small. In fact, more than a few times we have had 4 inches of snow on our onions and it has never caused a problem.
Care while Growing
The first 2 months of your plant’s growth is super important so make sure you are weeding regularly. Adding compost and mulch such as leaves and straw can help with soil moisture retention as well as keep the weeds down.
Pests & Diseases
The biggest pest problems can come from Thrips and onion maggots. These can be controlled with long crop rotations away from planting areas.
Diseases that affect onions are neck rot, basal, and pink rot. Neck rot can be avoided by not having excess moisture before harvest and curing onions properly.
Basal & Pink Rot can be controlled with long rotations and solarization of the soil
Step 4 – Fertilize Onions
Onions are also one of the few plants where I recommend adding a balanced fertilizer to the soil at planting time. Onions are heavy feeders and adding fertilizer will boost top growth.
It is best to get a soil test to make sure that you need this for your onions if you have good healthy soil they should do fine. However, if you want to get a bumper crop of big bulbs you will need to fertilize.
I like to water my onions a couple of times a year with a mixture of fish emulsion. Two tablespoons in a gallon of water or you can side-dress your plants with organic nitrogen fertilizer.
Step 5 – Harvesting Onions
Harvest time arrives when the tops start to turn yellow and fall over. I usually give them a week or two after that point to do their final maturing.
If the weather is going to be clear and dry for a few days it is okay for you to dig your onions and then just leave them there in the sun for a day or two to start drying. But after 2 days you need to bring them into a protected area. Be sure you don’t let them get rained on. To learn more about when to harvest onions check out this article.
Step 6 – Curing (Drying) Onions
Proper curing is essential if you want your onions to store for any amount of time. I like to dry my onions on this little drying rack in my garage. The rack allows for plenty of airflow. Plan on at least two weeks to dry. Curing is complete when the top layers of skin are dry and papery.
The tops need to have completely dried and there is no moisture where the tops attached to the bulbs. The tops should just pull off when they are done. You can never “over-cure” onions so when in doubt give them a few more days!
Step 7 – Storing Onions
Onions should be stored hanging in mesh bags or if you like you can leave the tops on and braid them and hang them somewhere. Onions like to be stored in a very cool spot and will last much longer if stored in temperatures around 45 degrees Fahrenheit.
Depending on the variety, properly stored onions can last 3 to 10 months. Read this post to learn more about how we get some onions to last in storage for 10 months! If you grow your onions properly, they may become one of those crops that you never have to buy from the store again. If you grow a long storing onion like we do you will have onions in storage for 8 or 9 months.
When your supply finally gives out your new crop will already be in the ground and you can use green onions to get you through till the new crop is in! Early spring is the time to get your onions planted so get them in as soon as you can!
What seedlings can you start in January?- Zones 5 & 6
I always debate the spacing of onions. Jeavons says 4″. I’ve tried it in the past and the onions just didn’t grow well for me. 6″ works well but uses more space. I’m thinking closer might be better. So this year a lot are 5″. I’ll see what the yield is like.
I’ve been growing them at 4 inches for the past three years and have had pretty good success. We don’t get quite as big of onions as we used to, but I’ve found that smaller onions store longer anyway.
Nice one
I planted my onions and leeks in the high tunnel this year because winter didn’t want to let go. I’m going to try seeding them in August, weeding carefully, and covering them with a low tunnel for the winter (I’m in Maine). We go through a lot of onions each year so I’ll order sets again to make sure I have Plan B, just in case.
Thank you so much for sharing this informative post at Good Morning Mondays. I haven’t ever grown onions but my daughter does and she had a great crop, must give this a go. Blessings
Can you tell me the difference between sets and starts? Thanks!
Karla,
Sets are little dormant onions. You can buy them at your garden supply store. You simply bury them just below the soil and they will sprout and produces onions.
Starts are live growing plants. They look like a very small green onions and they are planted with the bulb portion just below the surface and the tops sticking out. Planting buy starts always produces a stronger and larger crop. There are also many more varieties of starts available than sets. I hope that helps.
Thank you so much!!!
This is a great post on growing onions! I wrote a post on things to read before starting a garden. I will add this to the growing list! Thanks so much!
Thanks Kristi!!
Thanks! I just ordered our onions, I just need to figure out when I should put mine in the ground. I’m excited though! Those onions look amazing.
Jennifer, Stay tuned. I have a post on planting onions from starts in the works, it’s around 2-3 weeks out.
A lot of the tops in my onions have flipped to the side.. I read it can cause disease if that happens.. It’s not harvest time test,what can I do to prevent disease? Thank you
Ivonne, Unless you are in an area where onion diseases are really prevalent I wouldn’t worry to much about it. It would be preferable to water them using drip irrigation, that would keep water off the leaves. But if the tops have fallen over then there really isn’t much you can do. I don’t know where you live. Are you sure they are not ready for harvest? How long have they been in the ground? Onions usually need 4 to 5 months to mature.
I live in west Odessa tx.. I planted them 2 months ago.. And also how can I preserve them? I don’t have a garage the only place I can think of is the pantry but I don’t know if they will last long in there… Thank you!!
I live in west Odessa tx.. I planted them 2 months ago.. And also how can I preserve them? I don’t have a garage the only place I can think of is the pantry but I don’t know if they will last long in there… Thank you!!
It does seem odd that they have fallen over already if they are only 2 months old. It may have more to do with the variety than anything else. Have you had and big wind storms that blew them over? I don’t have any disease prevention advice for you now that they have fallen over.
Storage has everything to do with Cold and variety. You need to keep them between 35 & 45 degrees to get the longest storage. So in your case that may be a fridge is your only option. Also depending on the variety you planted they could last from 30 days to 10 months if stored properly.
Yes we have had very strong winds!! & also I didn’t keep track of the grass it grew as big as the onions ups.. .
Please could you advise me as to whether the flower should be cut off when it starts to form
Yes Jo, you should always cut the flower off on onions as quickly as you see it start to form. Leaving the flower on will affect both flavor and storage life.
Do you stop watering them at some point toward the growing season? I have just had no luck growing onions, they never fall over. I am in the Southern Willamette Valley of Oregon. It’s between the Cascade Mountain range to the east, and the Coast Range on the west. Great farmland, but this is a cool, moist, temperate climate.
It might have a lot to do with your moist climate. I always stop watering about 2 weeks before I harvest, AFTER the tops have fallen over. When do you plant your onions? Many people don’t realize how early you can get them in. I am in a Zone 5/6 garden (right on the boarder) and I plant mine the last week of March. They are quite hardy and you should get them in as early as possible.
We didn’t eat up all the harvested onions and now I got about 50 big onions that are growing in the bags. Will i get only stems if i plant my growing onions from last year?
Mary Ann, Great Question. Onions are Bi-Annuaual plants. That means that in the second year of growth (harvest or not) they will focus mainly on growing a flower and setting seeds. The bulbs will basically be ruined in this process. I’m afraid what you can’t eat up soon are pretty much a loss for the year! Sorry. You might want to consider growing a different longer storing onion. Try Copra, they are a good tasting variety that can last 10 months in storage if stored under the proper conditions. Look at this post for a little more info:
https://ourstoneyacres.com/curing-and-storing-onions-for-10-months-or-more
Last year, I made a mix of green pepper and onions (strips) and froze them for when we wanted stir fry. It was awesome! Don’t throw them away!
Pickle them!!
Caramelize them into an onion marmalade! Both csn last for quite some time, and i have frozen caramelized onions before, worked great!
I’m in northern California; my onions were planted in March and it’s inching toward harvest. Want to make sure I have the sequence correct: tops yellow and fall over; wait 2 weeks; dig; 2 days in sun; air dry 2-3 weeks; store cold. When do I stop watering?
I usually stop watering about 7 to 10 days before I harvest, so a week or so after all of the tops have fallen over.
Great post but I wanted to know of you have had less onions running to seed by growing with seed or sets. I grew from sets all the time in England but now I live in Utah I find that growing from sets means that nearly all my onions are flowering and I wondered if that was the norm here?
I’m going to be trying from seed next year too!
Emma, My preference is to grow them from starts (either ones I grow myself or buy from Dixondale farms). I agree with you, onions grown from sets almost always go to seed. That is because Onion sets are onions that were grown the year before and pick when immature. So even though they are small, the onions “think” they are 2 year old plants, and as bi-annual plants onions always put up a seed stalk in the second year. This year I planted just over 100 onions from starts. Out of those 100 plants only 3 sent up flower stalks! That is a huge difference and makes for a much healthier crop! Here’s a link to a post where I talk a lot more about seedlings: https://ourstoneyacres.com/planting-onions-using-seedlings
My problem is in the spring, it is usually too wet to get into my garden … I love planting onions, cabbage and early spring veggies ,but too wet…
One thing that I do to help make early spring planting possible is to make sure the planting beds and soil are all ready to go in the fall. If you have added you compost and done any digging before winter then in the spring as soon as the top dries just a bit you can get out and get things planted.
Do you need to put anything in with the onion sets when you plant them to avoid getting worms in the onions?
Although cool-season crops, onions can grow in warm regions of the United States, such as hardiness zone 7. If you plan to grow this vegetable in your garden, it is best to plant seeds or bulbs from January through March or sow from September to December. However, keep in mind that fall is a better growing season than spring.