We’ve all had it happen. That rogue onion that manages to hide at the back of the bin.
Once onions come out of cold storage and hit the supermarket shelves, it’s only a matter of time before they wake up and start trying to grow. The outside will become dry and papery, and the whole onion will shrink as it puts stored energy into trying to make one last go at life.
Once an onion has sprouted, there’s nothing wrong with eating it. Provided it’s not actually spoiling or molding, it’s still fine to cut up for dinner.
The problem is, there isn’t much usable onion inside at this point. Rather than trying to eat it, it’s better to invest in a good crop of future onions. If you can plant it, you’ll reap a reward 3 fold by the end of the season.
Dividing a Sprouted Onion for Planting
Onions are usually grown from seed, and a sprouted onion needs to be divided to grow properly. After the first growing season, if that onion had stayed in the ground instead of being harvested, it would have divided into multiple onions all on its own.
Each individual onion would be a bit deformed, as it competed for space with the others. By separating them, each onion can grow into a full-sized bulb, and allow you to harvest far more than you planted.
Start by peeling back the outer paper of the onion. Once inside, you’ll see that the onion has already started to section itself off into multiple onion plants.
Once you’ve peeled everything off, you should have multiple distinct onion sprouts. I had two onions sprouting in the back of my bin, and each of them had three individual onion divisions inside.
It’s not necessarily always going to be three, which makes it a bit of a mystery hunt. Even if you only have 1 or 2 green stems coming out the top, there may be other smaller plants inside that haven’t popped yet.
How to Plant a Sprouted Onion
At this point, you have tiny onion plants. In cold regions with a short growing season like ours here in Vermont, it’s actually common for gardeners to order in small onion plants like this from warm growing regions like Texas. With that in mind, actually planting a sprouted onion isn’t that strange a concept.
Onion sets, for example, are just small onion plant starts that have been harvested and cured to suspend their growth until they’re replanted. Onions are pretty durable, and even after you’ve basically ripped them apart and removed half their layers, they’ll still likely grow without issue.
Once divided, sprouted onions can be planted directly into the garden or potted up indoors.
Onions can handle a light frost and are generally planted outdoors from seed about a month before the last spring frost.
Your plants, however, have been tucked away cozily indoors and cold spring weather will be quite a shock. If it’s early, try potting them up and gradually introducing them to the outdoors to harden them off. If it’s mid-winter in a cold area, they’ll need to be grown completely indoors in pots until you harvest.
Onions are pretty easy to grow, but they can’t handle weedy competition and they need ample water in well-drained soil.
The time to harvest your new, full-sized onions will depend on how big their initial bulbs were at planting, and the onion variety. Generally, onion plants give you a head start on the season as compared to planting a seed, and gardeners harvest onions from started onion plants about 65 to 80 days after planting.
Keep an eye on your plants, weed them regularly and water them every few days. Soon enough, you’ll have several onions to replace that sprouted onion from your pantry.
Lorena
Thanks! I will give it a go!
Kiaya
I had an onion that got lost at the back of my crisper and this is perfect for it! Only has two small sprouts at this stage, thinking I will leave it for another day or two before splitting it! I live in sunny Queensland, Australia and the climate will hopefully be super easy for it to grow! Going to pop it beside my corn and parsley!
Brittany Rollins
I planted mine outside after it sprouted in my fridge. I left it planted outside for two weeks with regular watering until it had about 20-25 green stems. Then carefully dug it up and split it. I get at least 6 onions sprouts out of it every time.
Leanne
Don’t store onions/potatoes in your fridge! Put them in paper bags (not plastic) with a few holes cut in the bag. Cool dark place is best and they will last MUCH.longer!
Parth
i try it but it will take how much time ??
Ashley Adamant
Quite a while for full sized onions. Those are generally about 100 days from planting. That said, after about a month in the ground they’ll have put on a good bit of growth and you can harvest a smaller onion anytime from 30 days on.
Ann
Appreciate this info. Can’t wait to see my return thank you
Kad
How is the plant or plants doing
Terry Delveaux
After reading a Vermont farming book , I am intrigued with the natural way of making money, I do composts with all of nature in it I mean all of nature curing together for two years making the the strongest fertilizer on the planet. you have Ideas I will be using and have done many. The more Ideas with nature will make me even stronger.
nancy
Thanks, have always wanted to grow onions and nows my chance
Jenni B
Walked into my kitchen last night to find two brown ones had gone off managed to get 5 bulbs out 😍 as a new found green thumb I got overly excited haha
Doreen & John
Great info. You’ve inspired us to plant our sprouting onions in pots! Enjoying your blog!
Monica
Can I eat the green sprouts?
Ashley Adamant
Yes. Onion greens are edible (and tasty). Just watch out, if they get too old they’ll start to spoil and get slimy/brown, so be sure they’re fresh (just like any other produce).
Tas
I had a sprouted onion, i sliced the bottom quarter off and placed it in water to encourage new root growth. And as for the rest of the onion I peeeled away the layers and separated the sprouts – although the sprouts are no longer connected to the roots (they have raw flat ends after being cut) will they still grow new roots? Should I put them in water first before planting them?
Administrator
I would think that you would need to keep the roots intact but I am curious to know how it turns out.
Helen
Hello, I’m trying to separate the sprouting parts of an onion – but how do you separate the sprouts so each sprout has some of the root – just tear them apart and hope for the best ? Or is there a better technique?
Ashley Adamant
Yup, tear them apart and hope for the best is my technique and I haven’t had one fail yet.
Helen
Hello Ashley,
Thanks for the advice, I’ll do just that.
Helen
Natali Gaines-Fields
Hello, I planted the whole onion and it sprouted. Should I still divide it or will it still produce onions?
Ashley Adamant
If they’re right on top of eachother they’ll likely not produce full onions, and if you didn’t peel the outside off, mostly likely it’ll just use that energy to produce seed heads. Onions are biennial,and if re-planted whole they’11 usually just go to seed. The reason for separating them and removing the onion flesh around the outside is it kicked them back to their first year and they’re more likely to produce onions instead of seed heads.
So, that’s a long answer, but if you want a better chance of onions, dig it up and divide it. (The flowers are really beautiful though, like more than you’d imagine from a common kitchen onion, and the bees love them, so you can just leave it as an ornamental.)
Michelle
Thank you! I have planted an onion I named Manny, and now he is a wee little onion sprout in a pot. I hope to update you on his growth. Good luck to you
Michelle
I live in the PNW, is it still too harsh to plant them outside directly in June?
Edgar JEFFRIES
Here in England we call those scallions but you must use organic as cmmershal are sprayed to stop them sprouting we plant the whole bulb then separate when we harvest about July they tend to be hotter with more flavor
Gabriella Saghy
How deep should we plant the bulbs? Also, is it like garlic in the sense that I can plant the bulbs just before winter and harvest in spring?
Ashley Adamant
Plant the bulbs so that the whole bulb is in the ground and the stem sticking out. You can plant them in the fall, yes, but they’ll take a whole season the next year to make bulbs. You’ll be harvesting them in late summer or early fall.
Dortrean
You can cut roots off the bottom and plant them and have more plants
Ashley Adamant
Haven’t tried that method, but good to know!
Samantha
I found a sprouted onion in my fridge that I’d like to plant. It’s July and will get cold in a few months, is it too late to plant them in the ground? Should I put them in a pot instead? How big of a pot will I need? How many onions will one onion produce? Thanks!
Administrator
You could probably plant them outside but they won’t have time to get very big at this point. I would keep them inside in a pot and then in the spring you should actually have more sprouts to plant out. You can typically get somewhere around 3 sprouts per onion but it just depends.
Olutayo Okutubo
Can you just put it in water instead of in the dirt?
Ashley Adamant
They’ll need nutrients to grow into full-sized onions, but I’d imagine you could rig it so you could grow them hydroponically on a windowsill in water like that. What to add to make it work, I can’t say.
April Kelly
I placed the bottom of an onion in water after cutting and using it to cook with. Three stems sprouted. I separated them and placed them in dirt. Can I expect to see bulbs?
Ashley Adamant
You should, assuming they get enough sun. Good luck!
Ryan Shoemaker
Thanks. We always buy a bag of them and always have a few go “bad”. Just walked into my pantry and saw this time was the same. Thanks to a quick Google search and your information I hope to start growing my own. Psyched to try it out. Now to figure out planting squirrels. 😉
Admin
Awesome! I hope you enjoy it!
Deb Franklin
I am eager to try this. I have a couple that have sprouted and look ready to produce. About planting the roots that some have mentioned. I recently started cutting the root end out of the onion when prepping to cook. The reason is that I don’t like to have the root end in my dishes. I noticed that if I don’t cut it completely, a little sprout (if there is a sprout which I suspect has something to do with the time of year) usually comes out with the root. I have two sitting in a shallow water until I can get them planted. It’s an experiment. Can’t wait to see how both methods work. Hoping they grow well cause my family loves onion in everything.
Administrator
I love that you are experimenting with them. Let us know how it turns out.
Beth Reckinger, Az
Trying for the 1st time in pots. I have 2 sprouting onions s that I’m going to separate and see how many are inside. Super excited to give this a shot! Thanks for all the info!
Administrator
That’s great. So glad you enjoyed the article.
Marianne Nichols
How deep do you plant the bulb? Do you plant it so just the green is showing or deeper than that? If I have multiple onion pieces to plant, how far apart should I plant them?
Ashley Adamant
You plant them so the bulb is underground but the green is sticking up. I’d put them about 6 inches apart.
Trish Rose
Hi, this post has been so helpful, thanks! A question I have though is if I plant my sprouted onion bulbs into a pot (it’s February in Michigan) could I transplant them later to the garden in the Spring, or would they not do well being dug up once in a pot?
Administrator
You should definitely be able to transplant them into the garden.
Christine
Thank you-I planted one not knowing that I should separate the inside ones-seeing very soon my mistake-I’m really just growing the green sprouts….question: the green sprouts I have are large and numerous….can I not use them in cooking as well? Like for example use them the same way you might use chives? (chopped on something) because they certainly have an onion-y smell to them
Administrator
Yes you can definitely do that.
Corine
I am in Texas and the sun can get really hot. Should these be planted full sun or partial? Morning or event sun? Thank you!
Administrator
You want to be sure that your onions receive 6 to 7 hours of sunlight.
Tati
I don’t have enough room in my garden. Would I be able to grow them in a big pot outside in the sun? If so how big of a pot and how deep? Thank you!
Administrator
You want your pot to be at least 10 inches deep and as wide as you can get it. The wider the pot, the more onions you can plant. You need about 3 to 4 inches in between each onion to allow them proper room to grow.
Jessica
I’m In Scotland and the weather can be sometimes warm/ sunny or super cold. ( mainly cold and wet though even just now in the spring it’s been 2/3 degrees Celsius but the sun has been shining)
Where am I best planting? Will they be okay outside?
( I will be using a pot)
Just found a sprouted onion and really want to try to plant it! Never planted anything before so im a complete newbie.
Also is there a best soil to use?
Thanks
Administrator
If you are planting them in a pot, I would keep them indoors until they get established. Once you are ready to move them outdoors, you can place them outside for small periods of time and gradually increasing the time each day to harden them off. You can use any kind of potting soil to pot them up.
Terry Ann Robinson
THANKS FOR THIS INFORMATION, I LIVE IN SOUTH CAROLINA, WHEN WOULD IT BE SAFE FOR ME TO PLANT MY SPROUTS OUTSIDE?
Administrator
They can handle a light frost. But if they have been in the warm house, the cool spring temperatures can be quite a shock. You may want to try planting them in containers and allowing them to gradually harden off before planting outside.
Becky
So I found a sprouting purple onion at back of crisper. The sprouts are pretty good size 5-6 inches. Its end of July here in NC, region 8. Wondering if I put them in ground will they thrive or should I put them in a planter pots? Also how often and how much watering do they need. Help!
Administrator
I think you can definitely plant them outside.