You already paid for them. Now grow them again. For free.
Here’s the deal. Every bunch of green onions comes with a built-in plant. The roots. That pale little tangle at the bottom you’ve been chucking in the trash.
Don’t.
I regrow green onions on my windowsill year round. Takes about four seconds of effort. The payoff is an endless supply of fresh stems for salads, eggs, and whatever else.
This is the easiest plant on the planet. If you’ve killed every houseplant you’ve ever owned, start here. You almost can’t screw it up.
Why green onions and not, say, a tomato
Because green onions want to grow. Badly.
Most groceries you try to regrow are a science project. Green onions are a sure thing. Leave the roots in water and they’ll sprout whether you’re paying attention or not.
That’s the whole appeal. Low effort. High reward. My kind of math.
Quick botany note, since people always ask. The green onions at the store are usually just regular onions (Allium cepa) pulled young, before they bulb up.
Sometimes you’ll luck into Welsh onions (Allium fistulosum), which grow in clumps instead of bulbs. Either way, the roots regrow the same.
How to grow green onions in water
This is the lazy method. It’s also the one I tell everybody to start with.
- Cut your green onions like normal. Use the green tops for cooking.
- Keep the bottom inch or two, roots attached.
- Stand them root-down in a small glass.
- Add water until the roots are covered. Just the roots. Not the whole stem.
- Park the glass on a windowsill with some light.
That’s it. You’ll see new growth in a day or two. Seriously.
Change the water every couple of days. Skip this and it gets funky. Murky water means slimy roots and a bad smell. Fresh water means happy plants.
Harvest by snipping the green tops with scissors. Leave the white base in the glass. It grows back. Again. And again.
You’ll get two or three solid rounds out of one set of roots before they run out of steam.
How to grow green onions indoors in soil
Want more vigor and a longer run? Plant them.
Water-grown onions taste a little weaker each round. The plant is living off its own reserves. Soil gives it actual food.
Here’s my setup:
- A plant tray, or any pot with a drainage hole
- Peat-free, general-purpose potting mix
- Your green onion root ends
Poke the roots into the soil so the white base is buried and the cut tops stick out. Water it. Set it somewhere bright. A windowsill is perfect.
Keep the soil damp, not soggy. Snip the greens as you need them.
A soil-grown onion just keeps producing. You’re off the three-round clock now.
Want the kindergarten-craft version? Stick each root end in an empty toilet paper tube packed with soil, then line the tubes up in your tray. Keeps them upright. Looks tidy. Costs nothing.
What to actually expect
Let me set the bar straight so you’re not disappointed.
Your regrown onions will be thinner than the bunch you bought. That’s normal. They’re built for chopping, not for plating. Perfect in a salad. Great in a smoothie if that’s your thing.
You probably won’t get bulbs. These plants make stems, not onions. Leave one long enough and it’ll flower and go to seed. Collect those seeds, sow them in spring, and those plants will give you small bulbs. But that’s a different project for a different day.
For now? Free onions on the windowsill.
Look, you were going to throw the roots away anyway. Worst case, you’re out a glass of water. Big risk.
Best case, you’ve got onions growing on your windowsill for the price of nothing, in a space the size of a coffee mug.
Cut. Glass. Water. Windowsill. Do it tonight, forget about it, and check back in two days. You’ll be annoyed you didn’t start years ago. I was.
Davin is a jack-of-all-trades but has professional training and experience in various home and garden subjects. He leans on other experts when needed and edits and fact-checks all articles. Also an aspiring cook we he researches and tries all kinds of different food recipes and shares what works best.