How to Grow Green Onions: Everything From Growing Seeds To Saving Seeds!

I’ll get right to it: bunching onions will forever have a place in my garden. 

I’ve had them in my backyard for 3 years now, and they just keep getting better and better!

It started out as a small clump of bulbs I was given by a dog sitting client. She had an established patch in her garden and happily shared with me so I could start my own. I plopped them in the ground, and they’ve been thriving ever since. 

Now you might ask: how are they three years old? Do you not eat them?

Unlike the scallions you can get from the grocery store, I leave my bulbs in the ground and only harvest from the green tops. I suppose years down the road, when my garden is overflowing with them because I have no self control, I might pull a few and enjoy them whole. 😉

I’d like to walk you through what to expect when attempting to grow these from seed, from transplants AND indoors, as well as how I personally do it. And why you should highly consider adding them to your own garden!

Starting Them From Seed

For those in colder climates like me, direct sowing seeds really isn’t a reliable option since the growing season is so short. Here in Colorado, our last frost date is typically around the end of May, and our first frost is typically October 1. I like to start my onion seeds indoors in late January or early February to give them a good head start before transplanting them.

Use a good quality, light and fluffy soil mix. I personally use and recommend Pitmoss PM1 mix – it has a fantastic texture. Moisten the soil- not enough to be soggy, but wet enough to slightly stick together. For this step I find it easiest to control this by using a spray bottle. 

Sow the onion seeds by placing them on top of your soil then sprinkling a thin layer of soil right on top. Don’t cover them a lot. They’re itty bitty seeds and won’t be able to push through a thick layer once they’re sprouting!

Keep this container moist. If you have one, use a humidity dome to keep a constant moisture level. Or, make your own humidity dome out of an old deli or bakery container! 

Once the seeds have germinated and you see a bunch of little green threads starting to peek through the soil, place the container under a light source. As with any seeds you are starting indoors, the closer the light is to the seedlings, the healthier and stronger they will be. A light source that is too far away results in leggy seedlings. 

When the greens get about 4 inches tall or so, I like to trim off the tops. This encourages them to grow thicker and stronger. Plus, you get yummy onion greens to eat! I use them in a similar way to chives. 

A few weeks before the final frost in the spring, begin hardening off your onion seedlings. Don’t worry, they can handle a bit of cold. First time hardening off seedlings? See this article about how to properly do so. 

Your onions will look quite ridiculous and puny the first year. Don’t worry! This is normal. You’ll get a little bit of bunching action going on, but for the most part you’ll be tending to just one little bulb and a few main stems for this first year. 

But after that first year is when the magic really begins!

Wait… these survive over winter?!

Yes! Even here in the cold, harsh winters of Colorado, my bunching onions continue to survive. 

If you live in a cold climate like I do, the best way to set your onions up for overwintering is to pile some mulch around them. This will act as a nice thick scarf, protecting the roots from drastic temperature swings. 

We’ve dipped well below 0°F many times and they have done just fine. 

In the spring, you’ll know when things are warming up underground when you see bright green new growth on your onions. They’re one of the very earliest crops to awaken after wintertime, and what a glorious sight that is!

How To Get More Plants?

They aren’t called bunching onions for no reason. Once the onions are a bit older, they will begin to form new bulbs off of the main one. You can leave them be, and have a larger and larger patch every year. Or, you can divide them up! 

It’s quite easy to do, and they are a very forgiving plant when it comes to messing with their roots. 

Gently take a spade and dig down far enough to reach under the root system. Lift them gently out of the soil and shake them off to see what you have to work with. 

I like to separate my largest clumps every year and spread them around my property and to my gardening friends. 

Another way to get more plants is to collect your own seeds!

Onions are a biennial plant, meaning they will flower in their second year of life. The seed heads start popping up in spring, and will produce big beautiful flowers that pollinators LOVE. After they finish flowering, the flower heads will start to dry out and form seeds. You’ll want to collect the seeds once they are black and dry. 

I collect seeds from my hardy plants year after year to share with fellow gardeners. 

Store your seeds in a cool, dry place like a paper bag. For all things seed-saving, check out this article here!

Windowsill Onions

Even if you don’t have an outdoor garden, you can still totally grow green onions!

They are one of those neat plants that regrow from the roots. Yes, you can even try growing one that you got from the grocery store.

All you have to do is make sure you still have the roots attached to the bulb. It’s okay if they’re just little nubs! Plop it roots side down in a cup of water so that the roots are submerged.

In as little as a week, you’ll start to see new green growth come out of the top! You can cut these greens off and eat them, or you can transplant your new plant into some soil once it has some more roots established. I did this method all throughout college when I didn’t have access to a garden. It was always so fun seeing how quickly it regrew! 

That about covers it I think! Hopefully I’ve convinced you to give green onions a space in your garden. Once you get them established, you’ll be thankful years down the road when you can go out and snip some greens to add to your breakfast. 

Happy growing,

Becca