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

Your kitchen counter just became a mini onion farm—how to grow onions from onions in water couldn’t be simpler. That yellow onion sitting in your fridge? It’s hiding a secret—it can grow fresh green shoots in just 2 weeks with nothing but water and light.

I’ve done this every spring, and it’s the easiest way to get endless green onions without buying them. All you need is a shallow container, water, and a few onions.

The process is foolproof: place the base of the onion in water, keep it in bright light, and watch roots and shoots appear. No soil, no mess—just pure, fast growth that’s ready to snip for cooking in less than a month.

You’ll end up with 3-4 inches of tender green stems perfect for soups, salads, or garnishes. The best part? Once the roots grow, you can transplant them to soil for a full-sized onion plant that keeps producing all season.

Works for any onion variety, from sweet yellows to red storage onions. Here’s how to get started without overcomplicating it—no green thumb required!

What you need

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

Here's the simple method I use to get fresh green onions in weeks instead of months.

Choose firm, medium-sized onions with roots still attached—store-bought ones work fine. Cut off the top 1 inch of the onion, leaving a flat surface where the green shoots will emerge. I like to use a sharp knife and make the cut just above where the roots begin to cluster. This ensures you have enough root mass to support growth while keeping the stump stable in water.

Remove any loose or damaged roots from the base. Healthy roots should feel firm and white. If you see brown or mushy spots, trim those away—they won’t grow well. Place the prepared stumps in a shallow dish of cool water, making sure the roots are fully submerged but the onion itself stays dry. Change the water every 2-3 days to prevent rot and keep it fresh.

Place your onion stumps in a spot with bright, indirect light—a kitchen windowsill facing east or west works perfectly. Direct sunlight can scorch the emerging greens, so avoid south-facing windows unless you’re using sheer curtains. You’ll notice the first tiny sprouts within 3-5 days, but they’ll grow fastest when kept in temperatures between 65-75°F.

If your home runs cooler, place the dish on a seedling heat mat or near a warm spot like the top of the fridge. The roots need warmth to absorb water efficiently, which speeds up growth. Watch for the greens to reach about 2 inches tall before you transplant them—this usually happens within 2 weeks.

Once the greens hit 2 inches, carefully remove the stump from the water and let it sit for 10 minutes to dry slightly. This prevents the roots from getting waterlogged when you plant. Fill a small pot or garden bed with well-draining soil and dig a hole just deep enough to cover the roots but leave the onion stump exposed. Gently place the stump in the hole and press the soil around it lightly.

Water the soil thoroughly until it’s moist 1 inch deep, but avoid soaking the onion itself. Keep the pot in the same bright, indirect light for another 2-3 weeks, and you’ll see the greens thicken and lengthen. Harvest when they reach your preferred height—usually between 6-12 inches. Cut just above the onion stump, and you’ll often get a second flush of greens in 1-2 weeks.

After your first harvest, keep the onion stump in the soil and water it regularly, allowing the top inch of soil to dry out between waterings. You’ll likely get 2-3 more harvests from a single stump before it peters out. To encourage more growth, trim the greens back to about 1 inch above the stump—this tricks the plant into putting energy into new shoots instead of flowering.

If the stump starts to rot or the greens turn yellow, it’s time to compost it and start fresh. The whole process is surprisingly low-maintenance, and you’ll have fresh green onions ready in time for any recipe. I keep a few stumps going year-round on my windowsill, so I always have greens on hand for cooking.

Tips & tricks for growing fresh green onions from onions in water

These simple but game-changing tips will help you maximize your green onion harvest and avoid common pitfalls that can stall growth.

Selection Tip: Look for onions with firm, white roots that are still attached—these are your best bet for successful regrowth. I always check for any soft spots or brown areas on the roots before starting, because those can prevent the onion from establishing properly in water. Store-bought onions often work perfectly, but avoid any that feel spongy or have mold, as these won't regrow well.

Water Management: The key to preventing rot in Step 1 is maintaining clean water—change it every 2-3 days as instructed. I've found that using a shallow dish with just enough water to fully submerge the roots (about 1 inch deep) works best. Too much water can drown the roots, while too little can cause them to dry out and stop growing. A small glass or jar with narrow sides makes it easy to monitor water levels.

Light and Temperature Trick: While bright, indirect light is ideal, I've noticed that even a simple grow light placed 6-8 inches above the onions can work wonders if your natural light is limited. For the 65-75°F temperature range, keep an eye on your home's microclimates—kitchen windowsills near appliances can get warmer than you'd expect. If your home runs cooler, a seedling heat mat set to low can make a noticeable difference in growth speed.

Transplanting Technique: When transplanting after the greens reach 2 inches, I recommend using a small pot (4-6 inches wide) with drainage holes to prevent waterlogging. The 10-minute drying step before planting is crucial—it helps the roots adjust to the soil environment. I like to use a mix of potting soil and perlite for better drainage, which keeps the roots healthy and encourages faster regrowth after harvest.

Frequently asked questions

Can I use any onion to grow new green onions?

Nope! Only green onions (scallions) or bunching onions work—avoid yellow or red storage onions. These varieties regrow from their base because they’re actually immature plants.

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

With consistent care, you’ll see 1–2 inches of growth in 1–2 weeks. Once they’re 6+ inches tall, snip what you need and keep growing! Just change the water every 2–3 days.

What if my onion scraps rot in water?

This usually happens from bacterial growth or overcrowding. Fix it by:

• Using fresh, clean water daily
• Trimming the roots to 1 inch
• Adding a splash of hydrogen peroxide (3%) to sterilize
• Moving to a shallow container if too crowded

Can I transplant water-grown onions to soil?

Once roots form (after ~2 weeks), transfer them to well-draining soil with the base covered. Keep soil moist and place in sunny spots. They’ll keep growing like outdoor green onions!

How many times can I regrow green onions from the same scraps?

You can harvest 3–4 times before growth slows. After that, the scraps may weaken. For long-term regrowth, start fresh scraps every 2–3 weeks.

Will this work in cold climates or winter?

Yes! Place your container near a sunny window or under grow lights. Green onions tolerate cooler temps (down to 40°F/4°C), but avoid drafts. A warm kitchen windowsill is perfect!

Wrapping up and next steps

Growing onions from store-bought bulbs in water is a simple, rewarding, and budget-friendly way to enjoy fresh green onions in just two weeks! With minimal effort and a few household items, you can turn scraps into a thriving herb garden—perfect for soups, salads, or garnishes. 🌱

Now that you’re armed with the know-how, why not take the next step? Try experimenting with different containers or even transplanting your greens into soil for a fuller harvest. Happy growing—your kitchen (and taste buds) will thank you! 😊