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 need 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.
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
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).
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
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!