How to Plant a Sprouted Onion

This post may contain affiliate links. As an affiliate, I earn a commission.

So, you have an onion or two that you bought from the grocery store, that have now sprouted in the pantry. And you're wondering, "Can I plant these sprouted onions and regrow a new, fresh onion?"

In short the answer is, YES! You can plant a sprouted onion and grow a new one. Actually, usually you can get sometimes get three new onions from one sprouted onion!

But, you can't just plant the sprouted onion in the ground. You'll need to do a little bit of prep work first. Don't worry, it's not hard at all.

Here's how to regrow a sprouted onion...

Step 1

First, you need to peel the onion, layer by layer, down to the center.

Chances are some of the outer layers will be soft and maybe starting to rot if your onion has started sprouting. If not though, you can still use these outer layers of onion.

You want to peel all the way down until you get to just the clump of green sprouts.

I don't use a special tool for this. I just peel the layers off with my hands.

Step 2

Once you get to the center of your onion, then you want to carefully peel away the additional layers until you start to revel separate plants!

Usually each sprouted onion will contain three separate plants.

Step 3

Separate each onion plant by carefully cutting apart at the root with a serrated kitchen knife.

Step 4

Now it's time to plant your onion sprouts.

Your onion sprouts will survive for up to 3 weeks before you need to plant them. You do not need to store them in water or soak them before planting. Do store them in a cool dry place though to prevent them from rotting.

You will need to plant your onion sprouts in full sun.

Onions require a lot of light. 12 or more hours of direct sunlight is necessary.

How Deep to Bury Your Onion Plants

Onion plants don't need to be buried very deep. You should plant the seedlings just 1" into the ground and space them at least 4" apart so the bulbs have room to grow.

Planted onion sprouts will take about 3 weeks to look perky. Keep them watered and plant them in a place that gets plenty of sun.

FAQ: Can onions be planted indoors?

Onion plants are self-pollinators so they do not rely on insects to be pollinated. This means you can plant them indoors. However, onions require a substantial amount of sunlight to thrive. They need 12+ hours of direct sunlight.

Onions to not grow well in shade or even in indirect light. So if growing onions indoors, you will likely need to use a grow light to provide enough quality light to meet their needs.

Step 5

Continue to water and weed around your onion plants.

Onion plants prefer to be watered in cycles rather than every day. So you can water them about once a week unless the soil and plants start to visibly look too dry. Avoid overwatering as this can rot your onion bulbs.

Fertilize if your soil is not very rich.

Onions grow best in fertilized, well-drained, somewhat acidic soil and they like full sun. You can use organic (manure, compost, etc.) or store-bought fertilizer to ensure your soil has the nutrients it needs to nourish your onion to its fullest potential.

Your onions should grow for about 3 months to reach optimum size which is when the bulb reaches the size of a baseball. You will be able to see the top of the onion as it grows and can get a good idea of its size without digging it up.

You do not want your onion plant to flower. If it does, then you'll want to harvest that plant.

Step 6

Harvest your onions.

If your onion does not flower then you can let it grow up until the first frost.*

Harvest by pulling the onion out of the ground and then brushing them to remove dirt.

Do not wash onions. You want to keep the onions dry to avoid rot.

If you're ready to eat your onion, go ahead! They are ready to eat as soon as you pull them out of the ground. If you want to store them for later, read on.

*NOTE: If your onion plant flowers, unfortunately you will need to harvest whether it's full size or not. The bulb will not continue to grow once the plant flowers since all the plants energy will be redirected to the flower. Sometimes due to changes in temperature, the onion plant will flower prematurely. This can happen just as a fluke too so it's best to plant multiple onion sprouts for better odds of scoring a full-grown onion!

Step 7

Cure your onions for storage.

You do not need to cure onions. You can eat onions right out of the ground. However, if you plan to store them, then you'll want to cure them first. Curing is easy. It's essentially just drying out the onion and letting its skin become it's protective "container."

You can "cure" your onion for long-term storage by letting them sit in a warm place (75-80˚F) to dry up. You can hang them or place them in a wire basket or mesh bag with good airflow so all sides dry evenly. Trapped moisture may lead to rot so make sure all sides of the onion get exposure to air either by rotating the onion or hanging each onion individually. Some people lay them out in the garden and rotate them so all sides get a chance to dry out.

The green tops will dry up and the outside layer of skin will firm up. When the stems are completely dry, they are cured. Depending on the size and type of onion, it can take 2-6 weeks to completely cure the onion.

Storage

Once cured store your onions in a cool, dry place. Cured onions, depending on the type and size, can be stored for as long as 10 months!

And if your onion begins to sprout before you get to use it... you now know what to do! Use that sprouted onion to grow more onions!

Did you know you can also regrow a sprouted potato?

Learn how to plant a potato that has sprouted!

Now let's make some yummy food!

While you're here, check out my easy recipes to get ideas for what to make with your garden fresh onions!

Browse all my recipes