Growing Onions From Onions In Water: Regrow Green Stems in 2 Weeks

How to grow onions from onions in water could turn your kitchen scraps into fresh green onions in just 2 weeks—no soil needed. 🌱 I’ve regrown onions from store-bought bulbs so many times, my countertop looks like a mini farm. The secret? A glass of water, patience, and a sunny windowsill.

Start with firm, sprouting onion bulbs (the ones with green shoots already poking through). Trim the roots to about 1 inch, place them in 2 inches of water, and keep them in bright, indirect light.

Change the water every 2-3 days to prevent rot—this is where most beginners mess up.

By week 2, you’ll see 3-4 inches of lush green stems ready for snipping. The roots will be thick and white, signaling it’s time to transplant them into soil. You’ll get harvests for months—just keep cutting what you need and let the plant regrow.

Works for yellow, red, or white onions, and it’s perfect for small spaces. No garden? No problem. This trick saves money and waste while giving you fresh herbs year-round. Here’s how to do it without a single failure.

What you need

Step-by-step instructions for regrowing onions in water

Here’s how to transform store-bought onions into lush green stems ready for harvest in just two weeks.

Choose a firm, medium-sized onion with a thick base—avoid sprouted or soft ones. Cut off the top 1 inch of the onion, leaving the root end intact. This top piece should include the papery skin and the green shoot area. Discard the bottom ½ inch of roots if they’re mushy, but keep the healthy root plate.

Place the prepared onion in a shallow bowl or jar with just enough water to cover the roots by ½ inch. Use room-temperature water—cold water shocks the roots, while warm water can encourage rot. I like to use filtered water because chlorine can stress the regrowth. Change the water every 2-3 days to prevent bacterial buildup.

Set the onion in a spot with bright, indirect light—like a sunny windowsill or under a grow light. Direct sunlight can scorch the delicate new growth, so avoid placing it in the middle of a south-facing window. You’ll see tiny white roots emerge within 3-5 days, followed by a green shoot pushing upward.

Keep the onion in a well-ventilated area to prevent mold. If you notice condensation forming on the bowl, gently tilt it to let air circulate. The goal is to keep the roots submerged but the onion top dry. Mist the green shoot lightly with water if it looks wilted, but avoid soaking it.

After 7-10 days, the green stem should reach 2-3 inches tall, signaling it’s time to transition to soil. Watch for yellowing leaves or slimy roots—these are signs of overwatering or rot. If you see mold on the water, dump it and rinse the roots before refilling with fresh water.

Once the stem hits 4-5 inches, it’s ready to plant in soil. Choose a pot with drainage holes and fill it with well-draining potting mix. Gently place the onion in the soil, burying the root ball up to the base of the green shoot. Water lightly to settle the soil around the roots.

Harvest the green onions when the stems reach 8-12 inches tall—this usually takes 2-3 weeks after transplanting. Cut the stems at the base with clean scissors, leaving the root system intact. You can regrow the same onion up to 3 times by returning it to water after each harvest.

For a continuous supply, keep one onion in water at all times. Rotate between regrowth cycles so you always have fresh green onions on hand. Store harvested stems in the fridge for up to 1 week, or freeze them for longer storage. The key to success is consistency—keep the roots moist, the light bright, and the air flowing.

Tips & tricks for regrowing green onions in water

Here's what nobody tells you about turning scraps into fresh green onions—these tricks make all the difference between wimpy sprouts and lush, harvest-ready stems.

Selection Tip: The onion's condition determines your success. Look for a firm onion with a thick base and a papery skin that's still intact. Avoid onions with soft spots or sprouts already emerging—they won't regrow as vigorously. I've found that yellow onions regrow slightly faster than red varieties, though both work well. The key is that thick base where the roots will emerge.

Lighting Secret: Bright, indirect light is non-negotiable for healthy growth. If you notice your onion's green shoot leaning toward the light, rotate it daily to encourage straight growth. A south-facing window works beautifully, but if you're using artificial light, position the grow light about 6 inches above the onion and keep it on for 12-14 hours daily. Too little light results in leggy, weak stems that fall over easily.

Water Management: The water level is crucial—it should always cover the roots by exactly half an inch. Too much water causes rot, while too little prevents root development. I use a clear jar so I can easily monitor the water level. When changing water every 2-3 days, rinse the roots gently to remove any bacterial buildup. This simple step prevents that foul odor and keeps your onion healthy for the full regrowth cycle.

Transplanting Transition: When your stem reaches 4-5 inches, don't rush to transplant—wait until you see new roots forming at the soil line. This shows the onion has established itself enough to handle the soil transition. Use a pot with drainage holes to prevent waterlogging, which can cause root rot. The soil should be moist but not soggy, and you'll know you've done it right when new growth appears within a week of transplanting.

Frequently asked questions

Can I use any onion to regrow in water?

Not all onions work—choose green onions (scallions) or baby onions with a small bulb and firm roots. Avoid yellow or red storage onions; they lack the energy to regrow effectively. Look for onions with 1-2 inches of green shoots already sprouting!

How long does it take to regrow onions in water?

With proper care, you’ll see 1–2 inches of new growth in 1–2 weeks. Full regrowth (ready for transplanting) takes 4–6 weeks, depending on light and temperature. Patience pays off—consistent water changes and sunlight speed up the process!

What if my onion roots turn mushy or smell bad?

Mushy roots or foul odors mean root rot from overwatering or bacteria. Drain excess water immediately, trim any black/mushy roots with clean scissors, and refresh the water. Use fresh water daily and avoid overcrowding to prevent this.

Can I grow onions in water indoors without sunlight?

Yes, but you’ll need a grow light (LED or fluorescent) for 6–8 hours daily. Place the jar near a sunny window if possible, but artificial light ensures steady growth. South-facing windows get the most natural light—rotate the jar occasionally for even growth.

How do I harvest and use regrown onions?

Harvest by snipping the green stems 1–2 inches from the base when they’re 8–12 inches tall. For continuous harvests, trim leaves every 2–3 weeks—the bulb will keep growing! Store regrown onions in water (like celery) in the fridge for up to 2 weeks.

What if my onion doesn’t sprout at all?

Check these fixes:

1. Ensure the base is submerged (1–2 inches of water),
2. use filtered/room-temp water, and
3. place in warm, bright light. If no sprouts appear in 10 days, try a new onion—some may be past their regrowth prime.

Wrapping up and next steps

Growing onions from scraps in water is a simple, rewarding, and eco-friendly way to enjoy fresh green onions anytime! With just a few basic supplies and patience, you can regrow vibrant green stems in just two weeks—no soil or gardening skills required.

Whether you’re a beginner or a seasoned plant enthusiast, this method proves that even small kitchen scraps can yield big results.

Now that you’re armed with the know-how, give it a try today! Once your green onions are ready, experiment with them in salads, stir-fries, or garnishes. For even more fun, plant the roots in soil to grow full-sized onions—your future meals will thank you! 🌱