Did you discover some sprouting onions in your produce basket? Learn how to plant a sprouted onion in your garden in this easy gardening tutorial.
Follow our simple process and you’ll be able to grow a brand new onion in your garden! Fun activity to do with kids.
How to Plant a Sprouted Onion
- Sprouted onion
- Small glass of water
- Garden bed - or 5-gallon buckets filled with potting soil
- Cutting Board
- Cut carefully into the onion lengthwise to expose the center sprout. Be careful not to cut through the root of the onion.
- Remove the outer layers of the onion, until you just have the center sprout remaining. As long as the outer layers of the onion are still firm, you can eat them. If they're soft, discard them. If there are multiple sprouts like this one, separate them into individual onion sprouts.
- Place the onion stem into a cup or bowl of water and leave it there until new roots start to sprout. This new growth is the beginnings of roots. I like to leave them in the water until they're a bit longer before transplanting the onion sprout.
- Once you have roots developed, transplant the onion into the ground or a container full of good potting soil with the root end down. I didn't separate these ones, and they didn't grow right. Take my lesson and separate all of the sprouts before planting.
- Let them grow through the season. You can usually tell that the onion plants are done growing when you see the bulb emerge from the soil, or the green sprout starts to wilt and brown. If you leave them too long, they'll soften and rot. If you pull them at the right time, you'll have beautiful new onions that you grew practically for free!
Tips for Planting Sprouted Onions.
Several years ago, I figured out how to plant an onion that has sprouted in my garden to grow a brand new onion. Thousands of people have followed this tutorial to do the same.
Of course, you can grow your own onions from seed, get onion seedlings from your local garden center or go the super easy route and use onion sets from last season… but it’s so much fun to re-grow sprouted onions!
1. How often should I change the water?
Before planting the onions, you should change the water the roots are growing in once every 24-36 hours. If you let it go much longer than that, the water stagnates and can cause the onion or roots to rot.
2. Does this work with onions from the grocery store?
Absolutely, I have planted a ton of sprouted onions from the local market in our garden and in containers. They work great!
3. What types of onions work best?
White, yellow, red, Vidalia, sweet… it doesn’t really matter. It’s pretty much the same concept for all varieties of onion.
4. Can you re-grow Green Onions?
Yes, you can regrow green onion scraps too. You eat the green tops and grow from the roots. I show you step-by-step how in my blog post on re-growing green onions.
5. Can you plant onions that haven’t sprouted?
Over the years, I’ve found that you can also cut the center out of onions that haven’t started fully sprouting and regrow them! Just be very careful not to cut through the roots of the onion.
6. Can you plant a rotten onion that has sprouted?
Even if the onion is sprouting, if there are any black or rotten spots on the onion… just throw it away. If there are just a few brown spots or the layers of the onion are soft or a little mushy, but not rotten, you can use usually replant the sprout as long as it’s still firm.
7. Why can’t I just plant a whole onion?
I have tried planting whole onions, and I find that they have a higher tendency to rot in garden soil compared to planting just the sprout.
8. Container gardening and proper soil aeration.
Mixing in perlite, silica stones, small lava rock, small gravel, expanded clay pellets, coco coir or anything like that will help with drainage. This will help keep the soil from getting compacted, which will help bring oxygen to the plant’s roots and help the plant grow bigger.
A great ratio of perlite is 20-30% perlite to the soil. This will give good drainage while not drying the soil out too fast. I recommend watering your onions every 2-4 days, depending on your soil drainage.
Please do not overwater them… or they will rot.
9. How much room is needed when planting onions?
Regardless if they’re in the ground or in a container, you’ll want to make sure they’re 6-8″ from center apart. From my experience this allows the onions to have the space to grow larger.
10. What time of the year do you plant onions?
Onions are one cold-hardy crop that can usually be planted before the last frost. They do best in temperatures ranging from 50-75˚ F, but most varieties can handle temps all the way down to 20˚ F.
You can usually plan to plant them around 4-6 weeks before the last expected frost date (you can see 1st and last expected frosts in the different US zones on Morning Chores).
If you’re planting them in your garden outdoors, it’s best to plant them as soon as your soil is tillable in the early spring if you want a summer harvest.
If you have a short growing season and the ground doesn’t thaw until late spring or early summer, you can get a head start on your onion bed by starting them indoors in small containers, then transplanting them as onions need a long growing time to form large bulbs.
One great thing about planting onions in containers is that you can grow them year-round by taking them in and out of the house or even placing them near a sunny window if the ground is frozen.
11. How much sunlight do onions need?
For best results, plant your onions in full sun in your garden bed (they need 13-16 hours of sunlight daily while the bulbs are forming).
12. How to do you know they’re ready to pick?
You’ll notice that the green shoots and flower head starts to turn brown and wilt. Once that happens, it’s time to pick the onion before it rots.
If you want spring onions, be sure to pick the onion when you can see the top of the onion bulb above the soil, but before the green sprouts turn brown.
13. Eco-friendly tip: Recycle water!!!
Keeping two 5-gallon buckets in your shower and catching your shower runoff is a great way to water your garden plants as well.
14. Best way to store onions so they don’t sprout?
It’s best to store onions in a dark, cool, dry place. If they’re kept near a sunny window, they’ll be more likely to sprout sooner.
15. How to make this educational?
We like to make everything a learning experience in our home. If you have young kids, check out our free Kids Gardening Journal so your kids can document their onion’s growth!
16. What time of the year do I plant all of my vegetables?
If you would like to learn what time of the year to plant all of your vegetables, I highly recommend Pam Farley’s Vegetable Garden Planting Schedules. It’s a must for every gardener!!!