As a former organic market farmer, I’ve grown onions in every possible way. I’ve grown them from onion sets, from nursery-grown transplants, and from their little black seeds. Needless to say, I’ve learned quite a few tricks along the way, but I will tell you without a doubt that my best onion crops always start with planting onion seeds, not by planting onion sets or even by planting nursery-grown transplants. For me, planting onions from seed has always yielded the best results. But here’s the thing – you can’t just grow onions from seed like you do other vegetables. There’s a trick to doing it right.
Why planting onion seeds is better than planting sets
Onion sets are immature bulbs that were grown from seed that was planted in mid-summer of the previous year. The partially-grown bulbs are pulled from the soil in the fall and stored in a dormant state through the winter to be replanted the following spring. Many gardeners plant onions from sets because they’re widely available and it’s easy, but there are a few reasons why this may not be the best way to grow a good onion crop.
First, most gardeners make the mistake of choosing and planting the largest onion sets they can find when they should be picking the smallest sets instead. Texas A&M, Michigan State, and other university Extension Services note that bigger onion sets stop growing and go to flower sooner than smaller sets. When it comes to growing onions from sets, bigger definitely isn’t better; you’ll grow substantially larger onions by planting smaller sets.
Related post: Time-saving tips for the vegetable gardener
Onion sets are easy to find at garden centers, big box stores, and even in the produce section of the grocery store, but just because they’re easy to find, doesn’t make them the best onions to grow. Typically, only two or three varieties of onions are commonly available as sets, but there are dozens and dozens of onion varieties available from seed that are likely to do better in your garden. Just like growing tomatoes and peppers from seed, growing onions from seed means you’ll have a wider range of varietal options. But, exactly which onion varieties are best for your garden, depends on where your garden is located.
Which type of onion is best for your garden?
There are three different types of onions and picking the right type is key to growing a great crop.
- Short-day onions are varieties that form bulbs as soon the days reach 10 to 12 hours in length. They’re perfect for southern gardeners below the 35th parallel whose days are slightly shorter throughout the growing season. If you grow short-day onions in the north, you’ll end up with tiny bulbs that go to flower early in the season because the bulbs stop growing as the days lengthen. Common short day onions are ‘Southern Belle’, ‘White Bermuda’, and ‘Granex’, to name a few.
- Long-day onions are varieties that form bulbs when the days reach about 14 hours in length. They’re best for gardeners in the northern tier of the U.S. and Canada. Long-day onions won’t form bulbs south of the 35th parallel because the days aren’t long enough to trigger bulb formation. Common long-day onion varieties include ‘Walla Walla’, ‘Ring Master’, ‘Red Zeppelin’, ‘Yellow Sweet Spanish’.
- If you live somewhere across the mid-section of the U.S., grow day-neutral onion varieties (also called intermediate day). Varieties like ‘Red Amposta’, ‘Early Yellow Globe’, ‘Cabernet’, and ‘Superstar’ are a good fit. These varieties begin to set bulbs when days range from 12 to 14 hours in length.
Aside from the ability to grow a wide variety of the right onions for your climate, growing onions from seed also means you’ll grow larger bulbs. But, this is only true if you grow onion seeds the right way.
Two ways to plant onion seeds
Planting onion seeds under lights
Related post: The best way to start seeds: Grow lights or sunny windowsill?
Onions are cool-season crops that require 90 days or more to reach maturity. Because of this long growing season requirement and their preference for cooler weather, planting onion seeds directly into the garden in the spring makes it difficult for the bulbs to reach a good size before warm temperatures arrive. This means the seeds have to be started many weeks in advance of moving the plants outside into the garden. To make matters worse, onion seedlings are also slow growing. So, if you want to grow onion seeds indoors under grow lights, you should start them 10 to 12 weeks before it’s time to plant them into the garden in early spring.
But, planting onion seeds indoors under grow lights is a bit more nuanced than growing other vegetables from seed. When growing the seeds of tomatoes, eggplants, and other veggies indoors under grow lights, the lights should be on for 16 to 18 hours per day. But, if you grow onion seeds indoors under grow lights and leave the lights on for that long, it will initiate an early bulb set and result in puny onions. That means that if you want to start onion seeds indoors under grow lights, start very early and only leave the lights on for 10 to 12 hours per day.
To me, all of that seems like an awful lot of work, so I’m now planting onion seeds using a different method that’s far easier and a lot more fun. It’s called winter sowing.
My favorite method: Planting onion seeds via winter sowing
If you want to skip the hassle of grow lights, heating mats, and other seed-starting equipment, growing onion seeds via winter sowing is the way to go. It works like a charm and is super easy. All you need is a packet of onion seeds, a plastic lidded container, and some potting soil formulated for seed starting. I start planting onion seeds via winter sowing anytime between early December and mid-February.
Here are the steps I use to winter sow onion seeds:
- Poke three or four 1/2″ wide drainage holes in the bottom of the plastic container (I use clamshell-type take-out containers or empty plastic lettuce packages). Also make two 1/2″ wide ventilation holes in the top of the lid.
- Open the container and fill it with three inches of potting soil.
- Sprinkle the onion seeds on top of the soil, casually spacing them about 1/4″ to 1/2″ apart.
- Cover the seeds with a sprinkling of potting soil and water them in well.
- Put the lid on the container and label it with a piece of tape and a permanent marker.
Once the seeds are planted, put the container in a protected, shady spot outdoors. I keep mine on a picnic table against the back of our house. It doesn’t matter if it’s freezing cold and snowy outside when you plant the seeds; they’ll just sit dormant until it’s the perfect time for them to sprout (just like Mother Nature intended!). Don’t bother clearing off any snow or protecting the containers from freezing weather. The seeds will be fine.
Related post: How to cure harvested onions properly
When the temperatures and day length are just right, your onion seeds will start to sprout inside the container. At that time, you need to start monitoring the moisture level inside the container, watering your seedlings when necessary. Open the lid on warm days and close it at night. If you get a hard freeze in the spring, after the seedlings have germinated, toss a blanket or towel over the container at night for added insulation.
This video shares more about growing onions from seeds vs sets.
As soon as your garden soil can be worked in the early spring, transplant your onion seedlings out into the garden (that’s usually mid-March in my Pennsylvania garden). Unlike onion seedlings grown indoors under grow lights, there’s no need to harden-off winter sown onion seeds because they’ve been outdoors from the start.
Planting onion seeds by winter sowing means the plants are subjected to the natural day-night cycle right from the time of their germination. This means that bulb set is triggered at the correct time and the plants can form large bulbs before hot temperatures arrive.
For more on growing great onions, also visit our article on Perennial Onion Varieties, as well as our article on Curing Onions After Harvest. To learn more about winter sowing, check out our detailed article on Winter Sowing Seeds.
Try planting onion seeds instead of sets this year, and enjoy a prolific harvest of these beautiful bulbs.
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will winter sowing work for shallots?
I haven’t tried it, but I can’t imagine why it wouldn’t work. Give it a try and let us know how it goes.
Yes you can, they are even hardier than onions!
When I put shallot sets in the ground, I do it as the same time as I plant garlic in the late fall, not spring!
I enjoy your website and I read a lot and I’ve learned a lot from all the articles and things that you post on your website. I have a question do you think this sowing of onion seeds in the winter would work on potato seeds?
It might, but potatoes aren’t typically grown from seed as it takes quite a while for the plants to mature enough to form tubers. Typically when grown from seed, they need more than one season. I suggest starting potatoes from seed potatoes (which are not actually seeds) as per the info and instructions in this article: https://savvygardening.com/how-to-plant-seed-potatoes/
I always sow my onion/shallot seeds in flats at the end of Autumn then plant out as soon as the seedlings are able to be handled. Be careful when lifting them from the flat as you want as much root as possible on the plant. If you let the seedlings grow too big, you can trim the tops and the roots a bit to make planting easier. You have to keep the planted out seedlings moist so a soak hose and timer is useful. The seedlings will look a bit sad for a week, but will soon stand up and get growing.
When you plant out the seedlings, make a furrow about an inch deep and lay the seedlings 6 inches apart on one side of the furrow, then draw a little soil over the roots from the other side and press it down over the roots with a short piece of wood.
I need to try this method! How fascinating. I’ve had to “baby” my onion seedlings every year under lights. It will be nice to plant them and leave them to do their thing for a while.
Julia
Winter Sowing works for most plants, too, in my experience! They grow best when the time is right for them, and they know that time better than any of us and what we try to replicate with grow lights and perfect conditions. Plants are hardy and know what to do to thrive!
Even using indoor lights and putting them out in sheltered areas before finally transplanting them, my results were not as good as I had hoped. The seedlings were somewhat spindly. A couple of days ago I did my winter sowing and placed the plastic container in a shady area. Lets hope things work better for me !! I’m going to try it on some shallot and leek seeds too. Wish me luck, lol.
So, how did it work out for you?
Love this idea! I am in southern Alberta, zone 3/4 (I am on the boarder of those zones) It is Almost March 1st, is it to late to try this?
Thank you
Hmmm. That’s a good question, Maria. I’m not sure how it would work that far north. Try it with a few seeds and let us know if your growing season is long enough for it to work. I’m curious to hear your results!
I’m curious about the shady bit… Does “shady” mean “no direct sun at all,” or “shady most of the day?” When would you move them to a more sunny spot, when you transplant them?
I keep mine in full shade, though as the spring temperatures warm, I open the lid and gradually start to expose them to more sun in the week or two prior to planting them out into the garden. This isn’t a necessary step, but one that I do with my own crop.
I haven’t had much success germinating onion seeds and I’m very glad I found this website and your advice. It’s mid winter here in the Uk. so I’m going to try your method soon.
I’ve just read the article and yiur response. I planted seeds in an heated propagator in mid-january in a cold but well-lit room. They are now happily sprouting. I’m in the south of England.
Hi Kevin, Like you, I live in England in the Midlands. I am going to try this onion seed method.
Thank you Jessica.
Jessica, Thank you for a wonderful, informative website devoid of noisy, blinking advertisements. I realize that you need to pay for your time and expertise somehow, and I appreciate the tasteful way you’ve done that.
I’m anxious to try your onion seed planting method. I’ve never done it like this before, but just bought my seeds and have plenty of containers to work with. Will let you know the results this summer. Any suggestions on keeping the onion maggot flies at bay?
Thanks, Mary, for your kind words. We’re glad you enjoy the Savvy Gardening site. Report back with how your onion seed planting goes. As for the onion maggot flies, I suggest covering your onions with a layer of floating row cover (also called reemay fabric). It’s lightweight and translucent, so you can leave it over your onion crop from planting time until harvest. It will keep the female flies from laying eggs that turn into those nasty little maggots. Good luck!
On the winter sowing : is it watered and left to freeze/thaw/freeze/thaw … or do you leave it dry and let the elements water it through the top ventilation holes.
Water the seeds in right after planting and then leave it go. You may have to water it occasionally until spring’s arrival, but the condensation inside the container tends to keep it moist without any added input.
what zone are you in?
Hi Christina. I’m in Pennsylvania, Zone 5.
How large do the seedlings have to be before transplanting?
I used to do transplants but it’s expensive so I switched to sets. It might be too late to try seeds this season (It’s early Feb and I’m in zone 7) But I will give it a try next year.
Old timers used to say onions and leeks could be transplanted when they’re as thick as a hair on a dog, but I wait a bit longer than that to transplant mine. More like the thickness of embroidery floss.
Is the same true for bunching onions?
Yes. They can be started the same way.
Could you please give me the measurements on your plastic containers. My husband says, based on the picture with the board that they look to be about 18″ long. I say No, they are a little bigger than a strawberry container. As you said… about the size of a lettuce container. Thanks.,
Hi Barbara. The containers I use are about 16″x8″ and about 6-8″ deep, but the size is flexible.
Thanks Jessca. I was surprised they were that big. My husband will be hapoy he was right. I did plant two packets of onion seed as per your instructions. See photo. My container was about the size you said but not as deep. It does have a high plastic cover and should work. I have done winter sowing before but never tried growing onion from seed.
Hi Jessica, I’m so glad I found your site! I wondered if it’s too late for us to try winter sowing onions this year? We’re in zone 6a according to the USDA zone map. If it’s not too late, which onions would you recommend for us to try; I’d like to be able to store some after the season as well? Are their varieties that can store for longer periods of time? Thanks in advance! 🙂
Hi Jamie – Welcome to Savvy Gardening! Any of the long-day onion varieties listed in the article will work for your zone. They all store about the same, as long as they are cured properly and you ensure the storage conditions are correct. It’s definitely not too late to try winter sowing. Go for it! You’ll find more on how to properly cure and store onions here: https://www.gardeners.com/how-to/harvest-cure-store-onions/7366.html
Hi,
I just came across this and am wondering if it’s too late to try in the Philadelphia area. It’s alrwady March 10! Still worth a try?
It’s not too late. Give it a try!
Hi Jessica, I live in southern York co. Pa in zone 6b. I planted yellow and red onion seed in the middle of February. It’s been cold and I see no life in the bins. Please tell me they will sprout when it warms up and have time to mature. I followed your directions exactly, even have high mowing seed. Thanks
Michael
Hi Michael. Mine have just started to sprout here in Western PA. Don’t give up yet! They’ll sprout.
Does this same method work for leeks too?
Yes.
Would it be to late to try this method in central Wisonsin? Also, how do you transplant your seedlings? Do you just separate the seedlings a push them in the ground a couple is inches apart? Sorry, seedling myself!
You could certainly try it, but I would also start some seeds indoors under grow lights as a back up. Once the seedlings are a few inches tall, transplant them into the garden, spacing them about 4-6 inches apart. They’ll be hair-thin, but they grow quickly!
I had just about given up on my onion seed germinitating but today I checked again and they had finally germinated. It took 6 weeks. We had freezing temps and lots of snow so I didn’t think they would make t.
Would this work with other crops besides onions and if so which ones might work?
Yes. Most perennials are easy to start via winter sowing. You can do tomatoes and other warm-season veggies this way, too, but you should delay planting the containers until early spring and bring them inside if the weather is going to get very cold, especially at night.
Thanks for this great advice, Jessica!
How deep do you plant the onions during transplant? I’m afraid of planting too deep because I’ve never had luck with nursery transplants. I’ve got some seedlings that should have gone out weeks ago (I’m Zone 4) but I’ve been dragging my feet, afraid of screwing them up.
Hi Becca –
Plant them so the bottom third of the plant is below the ground. They aren’t overly fussy about how deep they’re planted.
Would this method work using seeds from last years seedheads?
I don’t see why it wouldn’t work. The only issue would be if the onions were a hybrid, the next generation would not come true from seed.
Hello Jessica,
Great idea! I live in Tulsa, Oklahoma and garden with raised beds. Instead of using a small container I’m thinking of planting my seeds directly into the raised bed and then covering the entire bed with a plastic sheet stretched across a frame. What are your thoughts on that idea? What drawbacks do you see with that approach?
I’m very interested in knowing if this idea worked. I want to use my raised beds as cold frames, but am not sure how, when and what to put in them.
Hi Jessica,
I live in north Idaho where we get winter temperatures near zero once in awhile but for the most part temperatures are around 20 degrees at night and low 30s during the day. My garden typically will have at least a foot of snow from Christmas until the spring thaw in March. Do you think I could sow Walla Walla seed directly into the garden in November? This would save the transplanting step. Thanks!
Great question. It’s quite possible that sowing the seeds in the fall would work well. Give it a try and let us know how it works out for you. This is how I grow my cilantro, spinach, lettuce, and mache. Haven’t tried it with onions, but why not give it a try?
Jessica, I planted my little onion plants and they did grow. I learned something in the process. I made the mistake of growing intermediate day and they just didn’t get the large bulbs I was expecting. I will use long day this winter when I plant again. This was my first attempt from seed. I’ve used long day sets in the past and got big bulbs but a lot would sprout and I would loose 20 percent in storage. Live and learn, hopefully. Thanks for your method, I know it will produce quality.
Jessica, I’d like to try your method but we go to Florida January through Mid March. We live just East of you near Somerset, PA. I have a hobby greenhouse should I put the container in there or put it on the back deck as you say. I ordered 135 day seeds ( 200 of them ), should I take half of them to Florida and start them there?
Hi Dennis. If you try this, I’d put them in the greenhouse as long as it doesn’t get too hot in there. I’m not sure how they’ll do without an occasional check-in for water and ventilation on warm days, but it’s worth a try! Let me know how it works out for you.
My greenhouse has an exhaust fan with thermostat, what temp should l set it at, 50 degrees? l’ll have someone check the moisture when they check on the house.
I think 45 to 50 degrees F would work fine.
Do you think this method would work for leeks as well? Onions, and the onion family, are new for my garden.
Yes. It should work for leeks, though they require a longer growing season and won’t be ready for harvest until the autumn or the following spring.
I am in Minnesota. I start onion seeds indoors. Put them in individual cells and do not disturb the roots. Then plant them in my garden in the spring. I put 10,10,10 fertilizer every two weeks. I get softball size onions that store well in the winter time.
Its early feb in south east PA, zone 6B. On tuesday till be 62 degrees and in wondering if i can now them directly and cover with agrobon.
Do you have any tips or warnings for me, or things I should look out for?
Thanks. Abigail
It’s too early to sow them directly into the garden, but you can grow them in lidded containers as described in the article. This affords them more protection than row cover and acts as a mini greenhouse. The seedlings can then be transplanted out into the garden in mid spring.
I’m in zone 9 is it to late to start seeds.
Hmmm… Zone 9 is pretty far south, but I still think it will work. Give it a try and let us know how you do.
We live in northwest Montana where it’s usually late March or early April before our garden is without snow and the soil able to be worked. OK to try this method and begin our seed about now? Can I assume they wouldn’t sprout too early before we are able to plant in the garden?
They sprout when the time is right, regardless of where you live. So, yep – I’d give it a try without hesitation.
I started Onions from seed for the first time last February. I was buying plants, sets and cell packs in the past. I had a great year in 2018 and will not go back to the old way. I like to grow Candy onions and this past year was my best yield.
Jessica,
I live in Kodiak Alaska we are having a very mild winter. Daytime temps in the mid 30’s to the mid 40’s. Night time temps in the mid 20’s to mid to high 30’s.I was going to plant directly into the greenhouse however i just read this article and like the idea. will this work in my area or is it to late this year. Our last frost date is around the end of may.
Hi Thomas. I think it would still work you, but I think you’ll want to do it asap. Let us know how it works out.
Have any of you tried transplanting 3 onion seedlings (from seed started indoors) together with each set of 3 spaced 9 to 12″ apart in a wide row grid?
No, but it sounds like an interesting way to grow them, Melody. I would worry that they would crowd each other out being planted that closely.
Hi, great article. I live in the Midlands, UK. Our weather is pretty much very similar to your northern states (no idea what zones they are) but without the freak cold snaps u get. Would this method work here too?
It sure would!
Hi!
My onions are doing well using your method. They are about an inch and a half tall but very thin. When would be the right time to plant them and how deep
Plant them out into the garden about 4-6 weeks before your last expected spring frost. They can tolerate cold spring temperatures. Bury them to about half of their height. I use a pencil to make a planting hole, drop the seedling in, and then tuck the soil around them snugly. And don’t forget to water them in!
Will this method work for USDA Hardiness Zone 4b?
Yes.
Hi Jessica! I am using this method for the first time. Zone 3 and started them in the container about 4 weeks ago. They were dormant for the first little while but are now about the size you described for transplanting (maybe even a bit bigger). Being in zone 3, we will likely still have some pretty cold nights (below freezing) for another couples weeks at least. The soil is workable and prepped and I have already seeded other cold weather seeds. So I think it should be okay? Unless you think otherwise…
How sensitive are the roots to transplant? Should I be gathering some soil up with the seedling as I transplant?
Thanks!
Hi Sara – Onions are very cold tolerant. I would suggest transplanting them out into the garden now that the soil has been worked. They’re tough little plants. Plant them deeply. I use a pencil to poke a slender hole and then drop the plants into the hole and snug the soil in around them.
I have pinions that grow every year,late July early August they go to seed can I plant them ? i heard some seeds need to be frozen is this true for onions? can onions be planted during summer?
Yes you can collect and plant the seeds or let them naturally fall. They’ll germinate the following spring.
Hello Jessica,
I live in Oklahoma, Zone 7a, and have already started some onion seeds. I planted a bunch of them in a cat litter box. They’re now 3-4 inches tall and under a grow light which runs for 9 hours a day. I realize now that I started them a bit early (you think??). What’s my best strategy for keeping these viable for planting next spring? Can I let them get pencil thick, then pull them, let them dry out, and use them as transplants; or should I try and let them grow (slowly) until next spring and then pull them and plant them?
Thanks in advance for your help !!!
Good question. I’ve never started them in the fall, so I’m not sure what advice I can give. Perhaps pull up the plants, pack them in a plastic bag, and hold them in the fridge for the winter. Then plant them out in the spring and cross your fingers. Sorry I don’t have better advice. No experience growing them that way.
I have to try this! I’ve only grown onion sets but a lot of my onions have some soft & brown spots. I’m in N.S. Canada zone 5b. Do you add any fertilizer at all or just plain seed starting mix?
Just plain seed-starting mix; no fertilizer as it can burn tender developing seedling roots.
Hi Sara, I’m right on the border of zones 6 & 5 and always leave a few green onions the ground. Usually they’ve grown tall enough to use at Easter dinner !
Hi Jessica, sorry I called you Sara on my previous post! Going to try your winter sowing method since I’ve never grown onions from seed. sounds interesting ! Also read an article onions prefer a lot of nitrogen during the first half of growing season. is this true?
I would not suggest using any nitrogen fertilizer on onions. Root crops use phosphorous to form big roots; too much nitrogen encourages excessive top growth at the expense of roots.
I just came across your post and had an Oh No moment, my onions and shallots have been under a grow light set to 16 hours for the last four weeks. Is there any way to determine if I’m already destined for disappointment? At the very least I now understand why my onions and shallots were miniature last year.
I wouldn’t throw them away. Just change the light settings and see how they do. You can also start a second batch and do an interesting experiment to see which grow better.
I came across this blog back in January, I then began to plan for my attempt. I’ve tried bulbs and seeds with minimal luck in the past. I couldn’t find any cheap containers of the right size, so I bought two clear totes at Wal-Mart for under $10 each. I planted my seeds (candy onion) in mid-January and had them on our back (covered) porch. I checked on them yesterday and each tote had one up. Today one or two more poked out. Our Michigan winter has been up and down but overall mild. I didn’t want them quite yet, but it’s all good. Now I’ll make sure that they get sunlight and protection from the freezing nights.
Hey Jessica! I tried your method and am hoping for some reassurance haha. I’m in zone 5a and am wondering if you think I should be seeing a sign of life soon. I planted my onions and leeks out in January and its now nearing the end of March. It’s still very cold here this year (we’re getting snow tomorrow), so maybe that’s why I’ve still got nothin’. I’m worried my little seeds may have drowned in the melting snow that once covered them, or were planted too deeply. What do you think?
Depending on your climate, it may be a few more weeks until the seedlings appear. Don’t fret about it too much. Perhaps move them into a spot with dappled sunshine and out of the full shade. However, if you have a very warm day, move them back into the shade so they don’t “cook”. Suddenly they’ll appear and they’ll grow like gang busters and they won’t stop until they’ve formed a good bulb and are ready for harvest.
Hi! I’m in PA (zone 6b) and am attempting winter sowing for the first time using my favorite variety of onion, the Tropea onion from Italy. I’ve been following your steps and advice the whole time! When/how do yo know it’s the right time to transplant to ground and what is the best way to go about doing that? My seedlings range in size and are about 2-4 inches in height, but thin, and some are still bent over. Thanks in advance for any advice you can throw my way!
The onions are ready to transplant out into the garden when they’re as thick as a strand of embroidery floss. The height doesn’t matter as much as the thickness of the seedlings.
Hi Jessica, I’m in Cape Cod, Massachusetts. Zone 7 A, I believe. It’s April 12th and I have seeds for long day onions. Can I still try planting them in a container to sew in the shade “winter sewing” or should I just direct sow the seeds in the earth now. What do you guggest?
I also have a “sun room” that has an outdoor deck for a floor so not heated, but on sunny days it gets very warm and there is lots of light.
My other question is this: I’ve just planted all of my garden seeds: tomatoes, asparagus, squash, cucumbers, beans, rhubarb, kale, brocolli pumpkin celery in pots and salad bins and covered them all with saran wrap. I’m wondering if I should put them in my dark furnace room for a few days to jump start germination, put them in y sun room where it gets cold at night or just leave them on my kitchen counter or dining room table where they will have indoor temps and some light. What do you suggest? Thank you, Tara
Hi Tara. Sure, you can try a late “winter sowing” of those onion seeds in plastic containers, or you could just plant them right in the ground. If it was me, i would do some of both for an interesting experiment. As for the rest of your seeds, I would keep them in the sunroom where they receive higher light. as long as the seeds are covered, there’s no need to keep them in the dark until germination.
Last fall when we planted our garlic, we also put in a row of onion seed, just to try it. We planted the seed about 1.5 inches deep. They are not up yet. Just wondering if we perhaps put the seed in too deep to come up?
Yes; that’s too deep for onion seeds. They really should only be about a quarter inch deep. Some may still sprout, but my guess is that most will not.
Hello Jessica, i live in northern Ontario i believe zone 4b, do you think it would work here? And if so which month should I start? And thanks for the interesting article.
Yes; it would work there. I would suggest starting them in early March.
Please do a follow up page about transplanting these seed sown onions… I ordered from the catalog. I didnt know if i should have let them dry out or put in water after they arrived. It snowed after I got them… So i waited…. I doubt more than two will make it… So please follow up with debth etc…
Have you ever tried growing onions from the bottoms of grocery store onion bulbs? Will that method form a new bulb? It’s all over the internet but I’m not sure if it’s a hoax.
I’m in Portland, OR (zone 8b)
It’s a great way to grow more onion greens/scallion tops, but regrowing onion bottoms doesn’t typically result in a new onion bulb.
Hi Jessica! First of all may I say thank you so much for this article and all the great information! I’m already inspiring to know as much as I’m sure you do about gardening, and also going to be raiding your website for any and all information! I have two questions, I live in like a between of zone 8 and 9 due to my elevation I think. We’re more likely to get snow then the town 30 minutes down from us but go 10 minutes up you get three feet of it lol. Any who, our winter is one that might get snow like maybe twice and a decent amount of rain. Our first fall frost is likely in late October (I’m just starting trying out this gardening ordeal so haven’t paid much attention unfortunately.) Do you have any suggestions of what month to start our winter sowing containers? Long day onions I’ve researched grow best in our area if that helps. So sorry for the page-paragraph just one more question, do you think you could do the winter sowing container method with garlic? Thank you so much in advance if you answer!
I suggest starting your seeds in February. Garlic is typically started from cloves, not from seeds. The seeds would take many years to grow into a full head of garlic. Happy gardening!
I’m in zone 4 and going to try this this year. I planted spanish onions from seed thy is year and they turned out an inch in size.
Thinking of using egg cartons instead . I can plant them right into the soil.
Thanks that was so helpful
So when you plant Seeds mid winter are you actuslly getting finished onions by the end of summer that same calendar year or just the little sets that you then replant for year 2 harvest as onion bulbs?
You are getting full-sized onions.
Hi Jessica- great website! I would like to try to grow onions in north central Florida-zones 9a-9b specifically- I think maybe vidalia style or texas sweet may work here as they are close to similar zones. The daylight nite cycle here does not vary as widely here as northern areas do- so think maybe can start seeds now- mid-October thru end of November for the 90 day cycle to complete before the 90 degree temps set-in in April. Any thoughts and possible sources of seeds friendly for this zone? Thanks- Bill
HI Bill – I think Texas Sweets would work well for you. Vidalias too, though they are particular about their soil. I suggest checking with Territorial Seeds to see if they have what you need.
Hi, I’m definitely going to be doing this. Can I use seed starting trays without the outer water tray? They do have vented lids.
Absolutely. Good luck!
I just read this article. Thnaks for this information. I was wondering way start in trays/containers if leaving outdoors anyway? Why not just plant the seeds in the ground in early Dec and mulch with straw, maybe put a row cover on in March/Apr to help them out? What is the benefit of starting in a container if it is left outside? I’m in zone 5 as well and I’m intrigued to start from seed as I’ve always used sets prior.
Hi Larry. You can try planting the seeds directly into the ground, but in my experience, they are likely to rot. Garden soil is much heavier and not as well drained as potting soil. Seeds that sit in wet, dense soil are more prone to rot. Plus, there are more potentially harmful fungal spores in garden soil that could lead to rot than there are in a sterile potting mix.
Hi – love this idea, but wondering if I could just plant the seeds in mid-January right into the bed? I am in NE Oklahoma, Zone 6/7
Hi Nikki – You certainly could give that a try. However, I’ve had trouble with the seeds rotting during the winter and early spring because I have very heavy garden soil. The potting soil used in winter sowing in containers is much better draining than most average garden soils, so the seeds are less likely to rot.
Would this all work with extreme winters, as we have here in Central Ontario? Last nights low was -22C and we have frost happening until mid May.
Yes. The seeds will not grow and germinate until conditions are right. They’ll just sprout a few weeks later that far north.
Came across this article. Trying this, never had much luck with onions. My wife and I have grown garlic over 20 years with very good results between 240 and 350 heads. We are always interested in new ideas and ways to get good crops. Thank you for sharing.
Great Info. really appreciate your help. Many Many Thanks JIM
I live in northern CA (Sacramento) zone 9. Thanks for the info about long/short day onions! My onions that I planted in the ground last fall are all beginning to form the seed stalk. They’re still young enough that I can use them like green onions. A couple years ago I had a variety that formed the biggest, nicest bulbs, but I have no idea what variety they were.
So if I understand your suggestions, for my growing area, I should choose long day onions. What time of year should I start the seeds? I assume I can plant them out whenever they are big enough to survive: they seem to winter over and not be impacted by the light frosts we get.
Yes; you would be long-day or day-neutral varieties. Start seeds in late winter or early spring for planting into the gardenas soon as the plants are as thick as a piece of embroidery floss. Onions tolerate heat well and will be ready to harvest when the greens die back and dry up, which should happen in late summer or early fall.
I’ve heard of this method before, but I wonder if a step can’t be left out. Is there a reason why I couldn’t dig a trench in my garden for the onions in late fall, wait ’til full freeze up, fill the trench with warm(ish) soil, plant the onion seed and leave it for spring and nature to take the next step? That way there would be no transplanting. I can leave ground cloth over them to provide the shade required (and insulate slightly) if needed. Then come spring, remove the ground cloth and let the onions do their business. Wouldn’t this accomplish the same thing as using the clam shells, but without the transplanting?
You could try this, yes. However, there’s a good chance the seeds would rot before germinating since garden soil stays much more water-logged than light, well-drained potting soil does. There’s also a chance you would loose the seeds to ants, birds, chipmunks, mice, and other critters who eat seeds. Try it, though, and see how it does. If the seeds survive, there’s no reason they shouldn’t germinate when the temperatures are right.
Hi! I tried your method for some onion seeds, however I think I transplanted them too soon. They are in a sandwich size plastic tub and will go into my raised bed. Should I wait until I see a onion bulb or until I see some type of root system?
Nope. When they’re as thick as a dog’s hair, it’s time to transplant. If you wait until there’s a bulb formation, there is a greater risk of transplant shock.
I planted the Spanish Onions seeds directly into my garden last fall and now they are up about 6 inches. I live in Saskatchewan, Canada (middle of the province) where it can get to -40 in the winter but they came up great so not to wait till harvest to see how big the onions are by then.
Hi, I used seed starting containers that are pretty small to start my onion seeds, is the depth of the soil extremely important? I also planted my seeds when it was 35 degrees and now its 55 with 50 degree temperatures forecast for the next week. Is that too warm?
Having a few inches of soil is important. If you have less, you’ll just need to transplant them a bit earlier in the growing season to give them more room to grow. If you have a few days in the 50s it is not a big deal. The seeds will sit dormant until growing conditions (including the day length, the soil temp, the air temp, and the soil moisture) are all perfect for supporting germination. On very warm days i suggest opening the container to keep it from getting too hot, but temps in the 50s or 60s or low 70s don’t require that.
You are wrong about where Onion Sets come from.
Onion Sets grow in the flower of the mother onion plant, at
the very top. Rows of them appear after the onion flower matures. They are not made in soil as you think .
Hi John. Some onion species, Egyptian walking onions for example) do produce small bulbs at the tops of their flower stalks (called bulbils), but they are not the sets you purchase for spring planting. Those are grown as described in the article.
Hi Jessica, I just found your site and suggestions for starting onion seeds! I’m in zone 7a, never tried planting onions from seed. I have a long day variety. Wasn’t sure when I should plant the seeds for my area in order to try the winter sowing method. Do you think the beginning of January is to early? I also have leek seed I would like to try. Thanks so much for all the info, I will be perusing your site oftern, I’m sure!
Hi Elizabeth – In your zone, I would start the seeds anytime from late December through early March. They will not germinate until the conditions are right no matter when you plant them.
Thanks for this great winter seed starting method.
I’ve done winter sowing for several cold-hardy veggies in the past few years and it worked fine in zone 7A. I found it works even better setting the containers under some row cover.
The last two years I “planted” the plastic jugs in the garden at the level of the potting soil. Then I covered with row cover. I got more, larger seedlings and they came sooner. This is because the garden soil temperature is generally warmer than the air temperature in January and February.
Great idea, Bill. Thanks for sharing!
I found this post mid February 2020. Thank you for such great information. I live in southern British Columbia. Prior to trying this method I had always started onion seeds under grow lights. This method worked extremely well and I won’t go back to grow lights for onions. Now if I could find an in depth post on curing them as that seems to be a big problem for us. Despite laying them out on wire racks in a shed and increasing air flow with a fan I always seem to have some that do not cure and end up rotting.
So glad you found the article useful, Elizabeth. And lucky you! We also have an in-depth article on curing onions on our site. You can find it here: https://savvygardening.com/curing-onions/
Wow! I found this article and decided to try your method for onions (I also did starters inside under a light. I am proud to say that my outside seeds are starting to germinate. I’m in CT and as you know, this week has been unseasonably warm. Hopefully, they make it. Thanks so much for sharing your knowledge!
I love this write article …i want to try this method as a beginner …I pray it produces nice results, I’m in southeast Nigeria.thank u
When doing the winter sowing, should I plant the seeds in rows, or can they be scattered around the surface?
I just scatter them, but there’s certainly nothing wrong with planting in rows if that’s what you prefer.
Thanks for this great article! My question is – how is winter sowing in a container that is left outside different/better than winter sowing directly in the garden? What are the advantages? Thanks!
The containers act like mini greenhouses so the soil and air in them stays warmer, especially on sunny days. The seeds germinate faster and the seedlings grow faster. So it gives you a jump start on the growing season. Plus the potting soil used in the jugs is lighter than the soil in your garden which usually translates to a reduced chance of seed rot.