Of all the money-saving garden tricks floating around, the one where you regrow green onions from the root ends actually holds up. You buy one bunch for about a dollar, use the green tops, and stick the white bottoms in water. A week later you’re cutting fresh greens again. It won’t feed a family, but if you use scallions a few times a week, you’ll basically never buy them again. And in October, when the outdoor garden is winding down, it’s a nice little kitchen project.
What you need
- A bunch of green onions with the roots still attached
- A small glass or jar
- Tap water
- A windowsill that gets a few hours of sun
That’s really it. Later on, a 6-inch pot of potting mix helps, and we’ll get to why.
Getting them started
When you chop the onions for dinner, stop an inch or two above the roots, so you keep all the white and a little sliver of the pale green too. Those stubs stand roots-down in your glass, and the water should come up over the roots and maybe halfway up the white part. Not the whole way, a stem that’s totally underwater just turns to mush.
Put the glass on a sunny windowsill. Two or three days in, there’s already a little green poking out of the middle, which is weirdly satisfying to watch. Give it a week, ten days tops, and you’ve got shoots 4 to 6 inches tall that are ready for the scissors.
Change the water
I’ll be real, this step gets forgotten all the time and then the glass is nasty. So every other day or so, tip the old water into the sink, give the roots a little rinse under the faucet and refill. If it’s gone cloudy on you or there’s a sort of swampy smell, yeah, that water’s been sitting a while. Keep it fresh and they’ll keep going.
Water vs. soil
Water works great for the first two or three cuttings. After that, the greens get thinner and paler each time, because the onion has used up the energy stored in its bulb and plain water has nothing to give it.
| Method | Time to first harvest | Number of good cuttings | Flavor |
|---|---|---|---|
| Water only | 7 to 10 days | 2 to 3 | Mild, gets thinner |
| Water, then pot of soil | 7 to 10 days | Many, for months | Stronger, thicker stems |
So when the roots look nice and white and healthy, that’s your cue to pot them up. Poke them into potting mix an inch down and about an inch from each other, give them a drink and put the pot right back on the windowsill. Planted like that they’ll keep you in scallions for months, and come spring you can even move them outside.
Harvesting
Use scissors and stay at least an inch up from the white part when you cut. Leave that base and it’ll grow back. If you pull the whole plant, it’s done.
Aim to cut when the tops are 6 inches or so. Taking a little at a time from several onions keeps all of them going better than chopping one down to the nub.
Things that go wrong
Slimy, mushy stems. Either the water’s too deep or it isn’t getting swapped out enough. Throw out the gross ones, rinse whatever’s left and fill the glass a bit lower.
Floppy, pale greens? Not enough light. A south or west window helps a lot in winter. If you don’t have one, a cheap LED clip light a few inches above works too.
No regrowth at all. Most likely the store trimmed the roots too short or they’d dried up already. Next time grab a bunch where the white ends are firm and there’s a good beard of roots hanging off.
Fruit flies. They show up when the water sits too long. Daily changes fix it.
A few more you can try
The same idea works for leeks, celery bases, and lettuce hearts, though those give you a smaller payoff. Green onions are the easy win. If you get hooked on growing food in small spaces, have a look at our budget container vegetable garden ideas. And if you want to try onions from seed next spring, our guide on how long seeds take to germinate gives you a timeline to plan around.
