How to Grow Scallions (Endless Green Onions on the Windowsill)

Yes — you can regrow scallions endlessly from the white root ends you’d normally toss in the bin. Drop them in a glass of water on a sunny windowsill and you’ll have fresh green onions in about a week, for free, forever.

This guide walks you through it step by step: water vs soil, how often to refresh the water, when to harvest, and how to keep one bunch producing for months instead of weeks.

Quick answer

Save the white root ends (bottom 3-5 cm / 1-2 in) of a bunch of scallions, stand them upright in a glass with 2-3 cm (1 in) of water, and place them on a sunny windowsill. Change the water every 2 days. New green shoots are ready to snip in 7 to 10 days. After the first or second harvest, transfer them to a pot of soil for months of regrowth.

Why regrow scallions instead of buying them

A bunch of scallions costs a couple of dollars at the grocery store, and the white root ends are the part most people throw away. Those root ends are a living, dormant plant — give them water and light and they finish growing for free.

Regrowing one bunch gives you, on average:

• A fresh harvest of green tops every 7 to 10 days for 4 to 6 weeks in water
• 6 to 12 months of slower, stronger-flavoured harvests once you transplant them to soil
• A small living plant on the windowsill that’s hard to kill

The cost is the bunch you already bought. The return is months of free green onions.

Scallions, green onions, spring onions — what’s the difference?

For this guide, all three terms mean the same thing: a young, slender allium with a small white base and long green tops, sold in bunches. Botanically, true scallions are usually Allium fistulosum (Welsh / bunching onion), which never forms a big bulb. “Green onion” is the most common US name; “spring onion” is the most common UK name. The regrowth method below works for all of them.

What you’ll need

• One bunch of fresh scallions from any grocery store
• A clean glass, jar, or short vase (narrow mouth keeps them upright)
• Filtered or tap water (let chlorinated water sit out for an hour first)
• A sunny windowsill — south- or west-facing is ideal
• Sharp scissors or a kitchen knife
• Optional, for long-term growing: a 15 cm (6 in) pot with drainage holes and general-purpose potting mix

Step-by-step: regrowing scallions in water

1. Trim the bunch

When you bring scallions home, use them in cooking as you normally would — but stop your cut 3 to 5 cm (1 to 2 in) above the white root end. That root end is what you’re going to regrow.

You should see fine white roots dangling from the base. If the roots are mostly intact and pale (not brown or slimy), you’re set.

2. Stand them in water

Drop the trimmed root ends upright into a clean glass with 2 to 3 cm (1 in) of water — just enough to cover the roots. Don’t submerge the white stem section. Onions in too much water rot.

A narrow-mouth jar or a tall shot glass works perfectly because it props the stubs up. If your glass is wide, a rubber band around the bunch keeps everything upright.

3. Set them in bright light

Place the glass on a windowsill that gets at least 4 hours of direct or very bright indirect light per day. South- or west-facing windows are best. New green shoots will start pushing up within 48 to 72 hours.

4. Change the water every 2 days

This is the single most important step. Stagnant water turns cloudy and bacterial, which makes the bulbs go slimy and rot at the base. Every other day, tip out the old water, rinse the roots gently under the tap, refill with fresh water to the same 2-3 cm (1 in) line.

If the water ever smells off, change it immediately and trim away any soft, brown, or mushy parts of the stem.

5. Harvest in 7 to 10 days

When the new green shoots reach 15 to 20 cm (6 to 8 in) tall, snip the tops with scissors, leaving 3 cm (1 in) above the white base so the plant keeps regrowing. Use the cut tops the same day for best flavour — they’re identical to the scallions you bought.

Your bunch will give you 2 to 3 strong regrowths in water before flavour and stem thickness fade. That’s your cue to move them to soil.

Moving scallions to soil for the long haul

After the first or second water harvest, you can pot up the bulbs to keep them producing for months instead of weeks.

1. Prepare the pot

Fill a 15 cm (6 in) pot with drainage holes about three-quarters full with general-purpose potting mix. Garden soil compacts in pots and chokes scallion roots — bagged mix is worth it.

2. Plant the bulbs

Make holes 5 cm (2 in) deep with your finger, spaced 3-5 cm (1-2 in) apart. Drop one bulb in each hole, white base down, green shoot up. Backfill loosely so the soil just covers the white section, leaving the green tops above the soil.

3. Water in and place in sun

Water until you see drips out the drainage holes, then put the pot in a sunny spot — at least 6 hours of direct sun outdoors, or your brightest windowsill indoors. New shoots from the soil are sturdier and have a stronger oniony bite than the water-grown ones.

4. Care from here

Task	When
Water	When the top 2-3 cm (0.75-1 in) of soil feels dry — usually every 4 to 7 days indoors, more often outdoors in summer
Fertilize	After 4 weeks, a balanced liquid fertilizer at half strength every 2 to 3 weeks
Harvest	Snip the green tops anytime they reach 20 cm (8 in), leaving 3 cm (1 in) above the soil
Divide	Every 6 to 12 months, lift the clump, separate the bulbs, and replant for a fresh boost

A free plant care app like Tazart can hold the watering schedule for you, adjust it for the season, and ping you when it’s time. Useful if you’re juggling scallions plus a few other windowsill edibles.

Common mistakes to avoid

• Submerging the whole bulb in water. Only the roots and the bottom 1 cm (0.4 in) of the white stem should sit in water. Anything more rots.
• Forgetting to change the water. Cloudy, smelly water = slimy bulbs in 2 days. Set a phone reminder for every other day.
• Leaving them in dim light. Pale, floppy shoots that flop sideways means not enough sun. Move closer to the window.
• Endless water-only growing. After the third regrowth, flavour fades fast. Plant in soil to extend the life from weeks to months.
• Picking a soft bunch at the store. Slimy, browning, or wet root ends won’t regrow. Pick a bunch with crisp green tops and clean white roots.

Troubleshooting

Symptom	Likely cause	Fix
White base turns slimy and smells bad	Water not being changed often enough	Tip out water, rinse roots, refill with fresh — every 2 days from now on
New shoots are pale and floppy	Not enough light	Move to a south- or west-facing window or supplement with a basic grow light
Shoots regrow but are very thin	Bulb is running out of stored energy	Move to soil and feed with diluted liquid fertilizer
Root ends never sprout	Roots dried out before going in water	Trim 1 cm (0.4 in) off the base to expose fresh tissue, restart in clean water
Tall flower stalk with a round head appears	Bolting (triggered by stress or age)	Snip the flower off; harvest the greens; divide the clump and replant the bulbs
Tiny black flying insects on soil-grown pots	Fungus gnats from staying too wet	Let the soil dry fully between waterings; top with 1 cm (0.5 in) of dry sand

Watch: regrowing scallions on the windowsill

A short visual walkthrough pairs well with the steps above. If you’re a visual learner, watch a quick tutorial like How to Regrow Scallions in Water on YouTube and then come back to follow the timing in this guide.

Related reading

• How to plant onions that have sprouted — same allium family, same easy “kitchen scrap to crop” trick, but for full bulb onions.
• How to grow lettuce in containers — pair scallions with cut-and-come-again lettuce on the same windowsill for a built-in salad station.
• How to grow basil indoors — the third member of the windowsill kitchen-garden trio.
• Scan the next plant you bring home with the free Tazart plant identifier and let it set up the watering schedule for you.

A note on conditions

Every kitchen is different. Light, water temperature, glass shape, season, humidity, and how fresh the original bunch was all change how fast scallions regrow and how long they keep producing. Use the steps above as a starting point and adjust based on what your bunch actually does in week two — that’s how every good windowsill grower learns.