Countertop HarvestBy the Countertop Harvest team · Last updated · How we choose products
Green onions are the easiest kitchen scrap we know of to regrow. Washington State University's Extension writer calls bunching onions possibly the easiest kitchen scrap crop to grow (WSU Extension), and the University of Florida describes buying scallions once as a way to get a steady supply (UF/IFAS). All it takes is the white root end, a glass of water and a bright windowsill. Iowa State Extension is realistic about the payoff: scrap growing won't replace a trip to the grocery store, but it is a fun project, especially with kids, and you get a little snack along the way (Iowa State Extension). Here is how we do it, in water and in soil.
Regrowing green onions in water
- Save the root ends. Use the green tops in cooking, then keep the white bulbs with the roots still attached (Iowa State Extension). UF/IFAS cuts off about the lower third of each scallion, the part with the roots (UF/IFAS).
- Stand them in a narrow glass. WSU says a narrow container works best because it keeps the onions upright (WSU Extension). A jar, cup or mug works fine (Iowa State Extension).
- Add just enough water. Iowa State fills the container with just enough water to keep the roots submerged (Iowa State Extension), and WSU keeps the top of the bulb above the water (WSU Extension). UF/IFAS fills until about half the stalk is under water (UF/IFAS). In our kitchen, roots under water and the top of the bulb above it works well.
- Give it light and warmth. Iowa State places the glass in a warm, sunny spot (Iowa State Extension), and UF/IFAS keeps it on a windowsill (UF/IFAS).
- Change the water. Iowa State changes the water once a week (Iowa State Extension), and UF/IFAS swaps it every few days (UF/IFAS). We change it whenever it looks cloudy and rinse the glass at the same time.
How fast it grows and how long it lasts
Iowa State says green shoots should begin to appear in a week or two (Iowa State Extension). WSU expects enough growth to trim within a week or a little longer (WSU Extension). We snip the new green tops as we need them and leave the bulb in place to keep going.
The regrowth doesn't last forever. Iowa State says the bulbs will produce shoots for a few months before they use up their reserves (Iowa State Extension). When a bulb starts to look soft or the new shoots get thin and pale, it is time to compost it and start a fresh bunch.
Moving them into soil
If you'd like stronger, longer-lasting plants, plant the bulbs in a pot. Iowa State suggests planting them once the shoots reach about 4 to 5 inches, either in a container or in the garden; for spring planting it starts the process around February and moves them outside after the last frost (Iowa State Extension). We use a pot with a drainage hole and regular potting mix, set the bulbs so the white part sits just below the surface, and keep the mix evenly moist.
Illinois Extension's Eat.Move.Save. program uses an even simpler setup: the white bulbs with roots in a shallow dish of water in a sunny window (Illinois Extension). For a longer-lived onion flavor on the counter, chives are a perennial alternative; see our guide to growing chives indoors.
Tips from our counter
- Start with healthy roots. We pick firm scallions with visible roots, since the roots are what the method depends on (Iowa State Extension; WSU Extension).
- Use bright light. A dim corner gives thin, floppy shoots. Our guide to how much light indoor plants need applies here too.
- Harvest a little at a time. Cutting a few shoots from each bulb lets them keep growing.
- Keep the glass clean. Fresh water and a rinsed glass help keep the water from turning cloudy or slimy.
Other scraps worth trying
WSU regrows lettuce and celery bases in a shallow dish of water, though it notes that celery grows new leaves rather than stalks (WSU Extension). UF/IFAS describes a different method for bulb onions: cut off the root end, let it dry for a day or two, then plant it in soil (UF/IFAS). Iowa State adds a useful warning for potatoes, sweet potatoes and garlic from the store, which are often treated to prevent sprouting, so a failed attempt is more likely the treatment than your skill (Iowa State Extension).
For another scrap project, see regrowing lemongrass from stalks.
Pets: keep onions away from cats and dogs
The ASPCA lists onion (Allium cepa) as toxic to dogs, cats and horses. Signs include vomiting, breakdown of red blood cells, blood in the urine, weakness, a high heart rate and panting (ASPCA). The ASPCA lists chives, another allium, as toxic too (ASPCA, Chives). We keep the regrowing glass on a sill the pets can't reach. If you think a pet has eaten some, the ASPCA asks you to call its Animal Poison Control Center at (888) 426-4435 or your veterinarian (ASPCA).
Common problems
Slimy bulbs or smelly water
The water has gone stale. Rinse the bulbs and glass and refill with fresh water. Iowa State keeps only enough water to cover the roots (Iowa State Extension), which helps keep the bulb itself from sitting in water.
No new growth after two weeks
Iowa State's timeline for shoots is one to two weeks (Iowa State Extension). If nothing has happened by then, try a warmer, brighter spot or a fresh bunch with healthy roots.
Thin, pale shoots
Low light or a spent bulb. Move it to a sunnier window, or plant the bulb in soil, or start over with new scraps.
Looking for something else to grow? Find a guide by plant.
Sources
- Iowa State University Extension and Outreach, Yard and Garden: How to grow vegetables from kitchen scraps
- University of Florida IFAS Gardening Solutions: Grocery store starts
- Washington State University Extension, Ferry County: Kitchen scrap gardening (2024)
- University of Illinois Extension, Eat.Move.Save.: Regrowing scrap veggies
- ASPCA Animal Poison Control Center: Onion
- ASPCA Animal Poison Control Center: Chives
All sources accessed October 20, 2026. This guide is about regrowing green onions at home.
Frequently asked questions
How long do green onions take to regrow in water?
Iowa State Extension says new green shoots should appear in a week or two, and Washington State University Extension expects enough growth to trim within about a week.
How often should I change the water?
Iowa State Extension changes it once a week, and UF/IFAS swaps it every few days. Change it sooner if it looks cloudy.
How many times can green onions regrow?
Iowa State Extension says the bulbs keep producing shoots for a few months before they use up their reserves. Planting them in soil once shoots reach 4 to 5 inches can give stronger plants.
How much water should I use?
Just enough to keep the roots submerged, according to Iowa State Extension. Washington State University keeps the top of the bulb above the water.
Are green onions safe around pets?
No. The ASPCA lists onion as toxic to dogs, cats and horses, and chives too. Keep the glass out of reach and call the ASPCA Animal Poison Control Center at (888) 426-4435 or your vet if a pet eats some.