How to Grow Onions from Onions in Water: Green Stems Ready in 2 Weeks

Your kitchen counter just became a mini onion farm thanks to how to grow onions from onions in water. That yellow onion sitting in your fridge?

It’s a free, ready-to-grow seed—no store-bought packets needed. This method gives you green onion stems in just 2 weeks, with zero gardening experience required.

The secret is in the roots: store-bought onions already have dormant root buds. Place the base in water, keep it bright, and watch those first pale sprouts appear within days.

No soil, no mess—just a clear jar, water, and patience. It’s the fastest way to get edible greens, and the plants stay productive for months.

You’ll end up with lush, crisp onion tops perfect for salads, soups, or garnishes—all grown from scraps. The real magic? These regrown onions often outperform store-bought green onions in flavor and texture. Plus, it’s a great project to try with kids or skeptical roommates.

Fair warning: the roots can get leggy if you forget to transplant. But once you move them to soil, they’ll keep growing strong—no more buying green onions again. Here’s how to do it right, step by step.

What you need

Step-by-Step instructions for growing onions from onions in water

Here’s the simple method I’ve used to grow fresh green onions in just two weeks—no soil, no mess, just crisp stems ready for your kitchen.

Choose a fresh, firm onion with a thick base—avoid those with sprouting tops or soft spots. I like to use yellow or white onions because they’re sturdy and store well. Cut off the root end (the white bottom) about ½ inch above where the roots begin. This ensures you keep the growing part intact while removing any damaged sections.

Leave the top green stems alone—they’ll be your new growth. If the roots are already starting to sprout, even better! Place your prepared onion base in a small glass or jar with about 1 inch of water covering the bottom. The water should touch the roots but not submerge the onion base itself. This keeps it stable while allowing roots to grow freely.

Set your jar in a spot with bright, indirect light. A windowsill facing east or west works perfectly—south-facing windows can be too intense, especially in midday. You’ll see tiny white roots emerge within 3-5 days, signaling your onion is happy and ready to grow.

Here’s the thing—if your onion starts to lean toward the light, rotate the jar a quarter turn daily. This keeps the stems straight and prevents them from growing lopsided. Watch for the water level to drop as the onion drinks it up, and top off with fresh water every 2-3 days. Stagnant water will encourage mold, so keep it fresh but not overflowing.

Within 7-10 days, you’ll notice the green stems starting to regrow from the top of the onion. This is your cue to keep the water level consistent—about ½ inch deep at all times. The stems will grow quickly, so you’ll have harvestable greens in just 2 weeks.

Harvest by snipping the stems with clean scissors or kitchen shears, leaving about 1 inch of growth on the onion base. You can regrow the same onion multiple times by simply trimming the stems and returning it to the water. I’ve reused the same onion base for up to 3-4 harvests before it starts to weaken. Store unused onion bases in the fridge wrapped in a damp paper towel to keep them fresh for future regrowth.

If your onion base starts to smell or develop a slimy texture, it’s a sign of rot. This usually happens when the water sits too long without changing. To prevent this, always use fresh water and avoid overcrowding the jar. If the stems grow leggy or pale, your light source isn’t bright enough—move it closer to a window or consider adding a small grow light for 12 hours a day.

Don’t worry if the onion base itself softens over time—that’s normal as it’s being used up. The key is to act quickly before the base turns mushy. If you notice mold on the water’s surface, dump it out and rinse the jar thoroughly before refilling. A little prevention goes a long way in keeping your regrowth process smooth and successful.

Tips & tricks for perfect onion regrowth

Here's what I've learned from growing fresh green onions at home—these little details make all the difference between success and disappointment.

Selection is Everything: When choosing your onion, look for one with a thick, firm base and a healthy green top. The thicker the base, the more harvests you'll get. I've found that yellow or white onions work best because they're sturdy enough to handle the regrowth process. Avoid onions with soft spots or sprouting tops—they won't regrow properly. In Step 1, that ½-inch cut is crucial—it removes any potential rot while keeping the growing part intact.

Light Source Matters: Bright, indirect light is non-negotiable for healthy growth. I've had the best results with east or west-facing windows—south-facing windows can scorch the delicate stems. In Step 2, if you notice your onion leaning toward the light, that quarter-turn rotation every day keeps everything straight. And remember, those 2-3 days between water changes are perfect for preventing mold while keeping your onion hydrated.

Harvesting Strategy: When you're ready to harvest in Step 3, always leave that 1-inch growth on the onion base. This ensures you can reuse it for future harvests. I've gotten up to 3-4 harvests from a single onion base by following this rule. For the first few harvests, the stems will be especially tender and flavorful—perfect for adding to soups, salads, or stir-fries right from your countertop.

Troubleshooting Rot: The key to preventing rot is fresh water and quick action. If you notice that slimy texture in Step 4, it's already too late to save that onion base. But you can absolutely reuse the jar—just rinse it thoroughly with hot water and a bit of vinegar before starting fresh. That 12-hour grow light recommendation is a game-changer if your natural light isn't sufficient, especially in winter months.

Frequently asked questions

Got questions about growing onions from scraps? We’ve got answers! Here are some of the most common queries to help you succeed with this easy, space-saving method.

Can I use any onion to grow new green onions?

Not all onions work—stick to green onions (scallions) or yellow/brown onions with a small root base. Avoid white onions or red onions (they’re usually too dry). Look for ones with a firm base and visible sprouts or roots!

How long does it take for green onions to regrow in water?

With proper care, you’ll see 1–2 inches of new growth in 1–2 weeks. For full regrowth (ready to harvest), it typically takes 3–4 weeks. Patience pays off—keep the water fresh, and you’ll have fresh greens faster than store-bought!