How to Grow Onions From Onions in Water: Regrow Green Stems in 2 Weeks

That onion sitting in your fridge might have a secret life—how to grow onions from onions in water is easier than you’d think. 🌱 I’ve regrown green onions from store-bought bulbs in 10 days, and the process is simpler than you’d think—no soil, no fancy tools, just water and patience.

Start with firm, sprouting onions (skip the soft ones). Trim the root ends, leaving just a ½-inch stub, then place them in a shallow container of water. Within days, roots will tangle like tiny fishing nets, and shoots will reach for the light.

The magic happens when you transplant them to soil—suddenly, you’ve got a kitchen garden that keeps giving.

By week three, you’ll be harvesting fresh green onions for salads, stir-fries, or garnishes. The best part? This method works indoors, on windowsills, or even under grow lights. Even my black-thumb phase produced results with this foolproof trick.

Troubleshooting is easy: moldy water? Change it daily. Stunted growth? Move to brighter light. And yes, you can repeat the process with the same bulb until it’s spent—talk about zero-waste gardening!

What you need

Step-by-step instructions for regrowing onions in water

Here's how I've regrown fresh green onions from store-bought scraps—no soil needed, just patience and a sunny windowsill.

Grab 4 onion bulbs with 1-inch green stems still attached. I always choose the freshest-looking ones—those with firm, white bulbs and vibrant green tops. Cut the roots off the bottom, leaving about ½ inch of root base intact. This small root section is all you need to regrow.

Place the cut bulbs in a shallow bowl of room-temperature water (about ½ inch deep). The water should cover just the roots, not the bulb itself. Change the water every 2-3 days to prevent bacterial growth. You'll see tiny white roots emerge within 3-5 days—that's your first sign of success.

Keep the water level at ½ inch deep at all times. Too much water drowns the roots; too little slows growth. I use a clear glass so I can watch the roots grow—it's surprisingly satisfying. Place the bowl in a spot with bright, indirect light (like an east-facing window). Direct sunlight can scorch the greens as they grow taller.

After 7-10 days, you'll notice new green shoots emerging from the top of the bulb. This is when things get exciting! The original green stem will keep growing, but the real magic happens when new shoots appear around the bulb's base. These are your future harvests.

Once the greens reach 3-4 inches tall, it's time to move them to a sunny windowsill (or under a grow light for 12-14 hours/day). This boosts chlorophyll production and makes the stems thicker and more flavorful. I like to rotate the bowl quarter-turn daily so the greens grow straight instead of leaning toward the light.

Harvest by snipping the outer green stems with clean scissors when they reach 6-8 inches. Leave the inner shoots to keep growing—this encourages multiple harvests from a single bulb. With proper care, you can get 3-4 harvests before the bulb starts to soften.

If your regrown onions keep thriving, you can transplant them to potting soil for even bigger harvests. Fill a small pot with well-draining soil, plant the bulb with the roots down, and water lightly. Keep it in full sun and water when the top ½ inch of soil feels dry. You'll get continuous growth for months this way.

Here's the thing—if you skip this step, your regrown onions will still produce fresh, mild greens for weeks. But planting them gives you a permanent green onion source that keeps coming back stronger every time you harvest.

Tips & tricks for regrowing green onions in water

Real talk: This method is one of those kitchen hacks that feels like magic. Here's how to make sure your onion scraps actually grow into fresh, usable greens instead of turning into sad, limp stalks.

Root Health: When you cut the roots to about ½ inch, make sure you don't crush the base. The root section needs to stay intact to grow properly. If you accidentally damage it, just trim off the damaged part—you still have enough to regrow. The key is keeping that small root section healthy and undisturbed during the first few days.

Water Level Watch: Maintaining that ½-inch water level is crucial. Too much water will drown the roots, while too little will slow growth. I like to use a clear glass so I can easily monitor the water level and root development. If the water level drops between changes, just top it off with fresh room-temperature water.

Light Strategy: Bright, indirect light is perfect for the first 7-10 days, but once your greens reach 3-4 inches, move them to a sunnier spot. I've found that a south-facing window works best for that final growth phase. If you don't have great natural light, a simple grow light on a timer for 12-14 hours a day will work wonders. The extra light makes a noticeable difference in the thickness and flavor of your regrown onions.

Harvesting Technique: When harvesting, always use clean scissors to snip the outer green stems at the base. This prevents damage to the inner shoots and encourages more growth. I like to harvest every 2-3 weeks, which gives me fresh greens while still allowing the inner shoots to keep growing. Just be careful not to cut too close to the bulb itself—leave about ¼ inch of stem attached.

Frequently asked questions

Can I regrow any onion?

Not all onions work! Only green onions (scallions) or bunching onions regrow well—avoid yellow or red storage onions (like the ones you’d peel). Look for plump, firm stems with white roots still attached for the best results.

How long does it take to see new growth?

Patience pays off! You’ll typically spot tiny sprouts in 3–5 days, but full regrowth (ready to harvest) takes about 2–3 weeks. Keep the water fresh, and you’ll see steady progress.

What if my onion turns mushy or smells bad?

That’s a sign of rot—usually from stale water or overcrowding. Dump the water, rinse the roots, and trim any slimy spots. Use fresh, room-temperature water and keep the jar in bright, indirect light to prevent bacterial growth.

Can I replant the regrown onion in soil?

Once the roots are 1–2 inches long and green shoots are 3–4 inches tall, transplant them into pots or directly into garden soil. Space them 4–6 inches apart for optimal growth. They’ll thrive with sunlight and regular watering!

What if I don’t have a jar—can I use something else?

No jar? No problem! Use a small cup, glass, or even a plastic container with holes in the bottom for drainage. Just ensure the roots stay submerged in water and the setup stays stable. A clear container works best so you can monitor progress.

Wrapping up and next steps

Growing onions from scraps in water is a simple, rewarding, and budget-friendly way to expand your green onion supply—no garden required! 🌱 With just a few basic steps and patience, you’ll have fresh, flavorful regrowth ready to chop into meals in as little as two weeks.

Whether you’re a beginner gardener or a kitchen enthusiast, this method proves that even small scraps hold big potential.

Now that you’re armed with the know-how, why not try it today? Grab a leftover onion, a jar of water, and start your mini indoor garden.

Once you master this trick, you can explore other easy regrowth projects—like growing herbs or lettuce—to keep your kitchen green all year round! 🌿