How to Grow Onions in Water

Co-authored by Steve Masley

Last Updated: July 30, 2024 Fact Checked

Growing onions in water is a great way to reuse kitchen scraps, not to mention a fun activity that helps kids learn about vegetables. This method offers a front-row seat to plant growth, as you can watch the roots extend into the water and observe the sprout growing out of the onion top. The assembly of this project is super simple; all you need are some onions, a clear glass, and some fresh water. While onions can grow this way for a few weeks on your windowsill, but you’ll want to eventually replant the bulbs in soil in order for the vegetable to grow to maturity.

Method 1

Method 1 of 2:

Growing Bulb Onions in Water

Download Article

Pour tap or filtered water into your clear jar until it is almost entirely filled with water.^{[1]
X
Trustworthy Source

Royal Horticultural Society
Leading gardening charity in the U.K. providing resources for identifying, growing and caring for flowers and other plants

Go to source}
2
Poke four toothpicks, equally spaced, around the circumference of an onion. In order for the onion to sit above the water without falling in, you will need to make sure the vegetable is supported. Make sure the toothpicks are placed just slightly below the middle of the onion.^{[2]
X
Trustworthy Source

Royal Horticultural Society
Leading gardening charity in the U.K. providing resources for identifying, growing and caring for flowers and other plants

Go to source}
- Preferably you’ll want to use an onion that has already sprouted. An onion that has already begun the growth process will have an easier time growing in water.
- If you want to forgo the toothpick method, you can fill a clear glass jar nearly to the top with small rocks or pebbles. Then, place the onion on top of the pebbles and fill the jar with water, ensuring that just the roots and base of the onion are submerged.^{[3]
  X
  Research source}
Advertisement
3
Set the onion, roots down, on top of the glass with the toothpicks resting on the rim. The roots and base of the onion should be immersed in water. This way, the roots will be able to take in water and allow the onion to grow while the rest of the onion is surrounded by air and not rot.^{[4]
X
Research source}
- Take time to make sure the toothpicks are properly supporting the onion so it doesn’t fall into the water. At this point, you may need to push the toothpicks deeper into the onion to ensure that the onion is well supported.
4
Place the glass with the onion onto a windowsill that gets plenty of sunlight. Onions need at least six hours of sunlight to grow well. You also want to make sure you don't forget about the onion, so find a nice sunny windowsill that is in a busy part of your home. Now, all that’s left is to wait and watch your onion to grow. Over a week, you will see the roots will grow into the water and a green sprout will rise from the top.
- Regularly change the water. Do this before the water gets murky or smelly. Gently lift the onion, replace the water, and place the onion back onto the top of the jar.
A beautiful green sprout will begin to emerge from the top of the onion within a few days. The entire sprout is edible and has a deliciously sharp, herbal taste. Take scissors and cut the green sprout from the top of the onion, then cut it into thin strips. Add the cut pieces to soup or salad as a tasty garnish.^{[5]
X
Research source}
6
Plant the onion in soil when you notice a flower stem emerging from the top. Growing an onion in water is a really fun way to watch the early steps of vegetable growth. However, the onion cannot grow this way forever. After a few weeks, a flower stem will emerge. At this point, you can either plant the entire onion in soil, or just discard the onion. After the onion has started to flower, it can no longer grow in water and must be potted in soil.
- You don't have to wait for a flower stem to emerge if you want to plant your onion sooner. Once you see white roots growing out of the onion, it's ready to plant.^{[6]
  X
  Expert Source
  
  Steve Masley
  Home & Garden Specialist
  
  Expert Interview. 20 March 2019.}

Method 2

Method 2 of 2:

Reviving Green Onion Scraps in Water

Download Article

1
Slice whole green onions where the white stalk meets the green leaf. Perhaps you already have a pile of cut green onions that you were going to throw away. If so, great! Just use those. If not, grab a fresh bunch of green onions (also known as scallions or spring onions) and carefully use a knife or scissors to make the proper cut.^{[7]
X
Research source}
- At this point, you should have a piece of white bulb around the size of an adult's pinky finger. It’s okay if there is a bit of green left as well.
- Use the discarded green onion bits as an ingredient. Green onions make an excellent garnish on top of dishes like ramen noodles or tacos. Slice it thinly and sprinkle over your meal to brighten up the dish wish color and flavor.
2
Place the green onion scraps root down into a clear glass. Find a glass or jar that is relatively narrow, so that the green onion scraps will be supported and held up vertically.^{[8]
X
Research source} These will be growing on your windowsill for a while, so you may want to use a decorative glass or a vase that will look nice in your kitchen.
- You can use a rubber band to tie the bunch together to provide additional support.
- One of the best parts about growing kitchen scraps is being able to watch them grow, so be sure to use a clear vessel so you can watch the magic happen.
3
Add enough water to cover the roots of the green onion stalks. You want the roots to be completely immersed in water, but pouring water a little higher up will make sure the green onions don’t use up all the water before you have time to refill it.^{[9]
X
Research source}
- You can use tap or filtered water for your green onions, just make sure it is clean, fresh water.
4
Place the glass filled with green onions on a sunny windowsill. Now, all you need for your green onions to grow is sunlight and time.^{[10]
X
Research source}
- Placing the green onions on a windowsill in your kitchen (or somewhere you walk past often) will give them enough light to grow while making sure you don’t forget about them.
The onions will drink up the water you’ve provided them, so keep a watchful eye on the water level so that they don’t dry out.^{[11]
X
Research source} After a few days, remaining water can get murky or develop a bad smell. If that happens, dump it out and refill your glass with clean water.
Within a few days, you will notice that green stalks are sprouting out of the white bulbs. Once they grow to about 8 inches (20 cm) long, remove the stalks from the water.^{[12]
X
Research source}
7
Cut the green sprigs off the stalk or plant the entire bulb in soil. The green onions will only grow so tall. Once the green stalk is 8 inches (20 cm) or more, you can either cut off the green stalk and use the green onion as an ingredient, or you can plant the entire thing in soil (roots, white bulb, and green stalk) and continue to watch it grow.^{[13]
X
Research source}
- If you cut the green part off the stalk at this point, you can place the bulb back in clean water, and it will regrow. Although this will work once or twice, within a few cycles the plant will stop growing.^{[14]
  X
  Research source}

Community Q&A

Search

Add New Question

Question

How will tomatoes germinate?

Donagan

Top Answerer

All you need to germinate tomato seeds are some moisture and a moderate amount of heat. You can germinate them in potting soil or even between two wet layers of paper towel.

Thanks! We're glad this was helpful.
Thank you for your feedback.
If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
Yes No

Not Helpful 2 Helpful 10

Ask a Question

200 characters left

Include your email address to get a message when this question is answered.

Submit

Video

Tips

Use fresh onions and avoid onions that have mold or that have started to rot. Since the onions are submerged in water, any mold or rot will continue to spread throughout the rest of the bulb.

Thanks
Helpful 7 Not Helpful 1
Frequently prune the onion leaves when it is long to promote growth to new sprouts.

Thanks
Helpful 4 Not Helpful 4