How to Plant Green Onions (From Seed, Sets & Kitchen Scraps)

Green onions — also called scallions or spring onions — are one of the fastest, most forgiving crops a home grower can plant. You can start them from seed, from sets (small bulbs), or by regrowing the white root ends from your last grocery run, and still be snipping fresh green tops within a few weeks.

This guide covers all three methods in full, with the care, harvest cues, and troubleshooting that separate a continuous supply from a failed scrap-jar experiment.

Quick answer

Sow green onion seeds 0.5 cm (¼ in) deep, or press sets 1.25 cm (½ in) below the surface, spaced 2.5 cm (1 in) apart in rows 15 cm (6 in) apart. No thinning needed. Keep soil moist at 15–21°C (60–70°F). Harvest when tops reach 20–30 cm (8–12 in) — roughly 60–80 days from seed, 30–40 days from sets, or 7–14 days for a first cut from kitchen scraps.

Green onion, scallion, spring onion — what’s the difference?

These names are often used interchangeably, but they refer to slightly different things depending on context:

Name	What it usually means
Scallion	Allium fistulosum — a true bunching onion that never forms a bulb; mild, hollow round stems
Green onion	Common US term for any immature onion harvested young, including A. cepa sets pulled before bulbing
Spring onion	UK/AUS term — same as green onion; sometimes has a small round base
Welsh onion	Allium fistulosum — perennial, returns each year, clumps and divides easily

For this guide, the terms are used interchangeably — the planting methods, depths, and spacings are the same regardless of which name your seed packet uses.

Table of contents

1. Why green onions are different from bulbing onions
2. Method 1 — From seed
3. Method 2 — From sets
4. Method 3 — Kitchen scrap regrowth
5. Ongoing care
6. Harvesting
7. Common mistakes
8. Troubleshooting table
9. FAQ

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Why green onions are different from bulbing onions

This is NOT the same as planting onion bulbs for full-size storage onions. That post covers bulbing Allium cepa sets planted pointed end up at 2.5 cm (1 in) deep, spaced 10–15 cm (4–6 in) apart, harvested 90–120 days later when the tops fall.

Green onions are planted and managed differently:

• Shallower depth: 0.5 cm (¼ in) for seed, 1.25 cm (½ in) for sets — not 2.5 cm (1 in)
• Much closer spacing: 2.5 cm (1 in) apart, not 10–15 cm (4–6 in)
• No thinning required: dense stands are normal and desirable
• Harvested young: at 20–30 cm (8–12 in) tall, not at maturity
• Multiple harvests: snip and regrow 2–4 times from the same plant
• Fast: 30–80 days instead of 90–120 days

If you’ve already grown a sprouted onion from a store-bought bulb, you know the scallion-style harvest well — the same “snip the greens and let it regrow” principle applies here.

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Method 1 — From seed

Growing from seed gives you the widest variety selection (over 20 cultivars available, including Evergreen Hardy White, Parade, and Tokyo Long White) and the lowest cost per plant.

Timeline: 7–14 days to germinate → 60–80 days to first harvest.

What you’ll need

• Green onion or scallion seeds (heirloom bunching types recommended)
• Seed-starting mix or fine, well-drained potting compost
• A container at least 15 cm (6 in) deep, with drainage holes
• A sunny window or outdoor bed with 6+ hours of light

Seed planting steps

1. Prepare your bed or container. Fill to within 2.5 cm (1 in) of the rim. Water thoroughly and let it drain before sowing — wet-but-not-soggy is the target.

2. Open shallow furrows. Use a pencil, chopstick, or your fingertip to draw lines across the surface 0.5 cm (¼ in) deep, spacing rows 15 cm (6 in) apart.

3. Sow seeds 2.5 cm (1 in) apart. Drop one seed every 2.5 cm (1 in) along each furrow. Cover with the finest layer of soil — barely 0.5 cm (¼ in). Seeds deeper than 1 cm (½ in) germinate poorly.

4. Water gently. Use a mist sprayer or a watering can with a fine rose head. Heavy direct water disturbs tiny seeds and washes them together.

5. Keep moist and warm. Ideal germination temperature is 15–21°C (60–70°F). Germination takes 7–14 days. Don’t let the surface crust over and dry out during this window — thin crust is the main seed-germination killer.

6. No thinning needed. Dense seed stands are standard for scallions. They grow perfectly well shoulder to shoulder.

Succession planting tip

Sow a new small container or row every 3 weeks. Each batch reaches harvest at a different time, giving you fresh green onions continuously through the season rather than one large glut.

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Method 2 — From sets

Sets are small pre-grown onion bulbs, similar to what’s described in the onion bulb planting guide — but planted shallower and much closer together for the scallion harvest style.

Timeline: 30–40 days to first harvest.

How to plant sets for green onions

1. Source small sets. Sets meant for green onion production should be no larger than 1.5 cm (½ in) in diameter. Very large sets are more prone to bolting.

2. Plant 1.25 cm (½ in) below the surface. Unlike bulbing onions (which go 2.5 cm / 1 in deep), green onion sets go shallower — the tip should just barely sit below soil level, with the top of the set nearly flush.

3. Space 2.5 cm (1 in) apart. Row spacing 15 cm (6 in). This close spacing is intentional — green onions compete well and the dense stand produces uniform upright growth.

4. Firm gently and water in. Press the soil lightly around each set. Water with a fine-head can until the soil is thoroughly moist.

5. Mulch lightly. A 1 cm (½ in) layer of fine compost or straw between rows retains moisture and prevents the soil surface from baking dry.

From sets you’ll see green shoots within 5–7 days and harvest-ready tops in 30–40 days.

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Method 3 — Kitchen scrap regrowth

This is the viral “green onions in a glass of water” trick — and it genuinely works, with one important caveat: water alone depletes the bulb’s stored energy within 2–4 cuts. Transplanting into soil after the first water-regrow extends the plant’s life significantly.

Timeline: 7–10 days for first cut from water; 3–4 more cuts once in soil.

Step 1: Save the root ends

When you use store-bought green onions, cut the tops to use in cooking and set aside the white root ends — at least 2.5 cm (1 in) of white base with the roots still attached. Dry, shrivelled, or mouldy ends won’t regrow.

Step 2: Water-regrow phase (optional but popular)

Stand the root ends upright in a glass or jar with 2.5 cm (1 in) of cool water. The roots should be submerged; the cut top should be above the waterline. Place on a bright windowsill.

• Change the water every 1–2 days (stale water grows bacteria that rot the base)
• Within 3–5 days you’ll see green shoots emerging from the cut top
• After 7–10 days the shoots are 10–15 cm (4–6 in) and ready for a first snip

Step 3: Transplant into soil for sustained harvests

After the first water-based cut — or even before it — move the root ends into soil:

1. Fill a pot at least 10 cm (4 in) deep with moist potting mix.
2. Make a shallow well and nestle each root end in, barely covering the roots with soil, 2.5 cm (1 in) apart.
3. Water in gently and place in a spot with 6+ hours of light.
4. The plant transitions from water-feeding to soil-feeding within 5–7 days.

In soil, a well-lit kitchen-scrap root end produces 3–4 harvests before vigor wanes. This pairs perfectly with the trick in the sprouted onions guide — same principle, same pot.

Note on “indefinite regrowth” claims: You cannot harvest green onions indefinitely from the same root. Each cut weakens the stored energy in the white base. After 3–5 harvests from one root end, the stems become thinner and slower. Start a new batch of seeds or scraps every month for a continuous supply.

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Ongoing care

Green onions are low-maintenance once established. The three things that matter most are moisture, light, and soil temperature.

Watering

Keep soil consistently moist — not soggy. The top 1–2 cm (½ in) drying out briefly between waterings is fine; letting it dry 3–4 cm (1–1.5 in) deep causes tip-browning. In containers, check every 2–3 days in warm weather.

Avoid overhead watering once tops are tall — wet foliage overnight encourages fungal issues.

Temperature

Green onions are a cool-season crop. The sweet spot is 15–21°C (60–70°F). They tolerate light frost (down to about -3°C / 27°F) and can be planted 4–6 weeks before the last frost in spring.

At temperatures above 27°C (80°F), growth slows and plants may bolt (send up a flower stalk). Plant in part shade during summer in hot climates, or switch to a heat-tolerant variety like Evergreen White Bunching.

Fertilizing

Green onions are light feeders but respond to a boost of nitrogen every 3–4 weeks. A dilute liquid organic fertilizer (fish emulsion, liquid kelp, or balanced 10-10-10 at half strength) applied every 3–4 weeks keeps growth lush and fast. Don’t over-fertilize — excessively lush tops become floppy.

Companions and rotation

Green onions grow well alongside carrots, tomatoes, and asparagus — the allium scent deters some pests. Avoid planting in beds that had onions, garlic, or leeks in the past 2–3 years to reduce risk of white rot and downy mildew.

Garlic cloves and sprouted garlic make excellent rotation partners — they occupy beds in opposite seasons from green onions in many climates.

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Harvesting

When to harvest

Harvest green onions when:

• Tops are 20–30 cm (8–12 in) tall
• The white base is at least 1 cm (½ in) wide
• Leaves are firm and upright — not floppy or yellowing

Two harvest methods

Method A — Snip and regrow: Use clean scissors to cut the green tops 2.5 cm (1 in) above soil level. Leave the white base in the ground. The plant regrows from the cut point and produces another flush in 2–3 weeks. You can repeat this 2–4 times per plant.

Method B — Pull the whole plant: Grasp at the base and lift the entire plant, roots and all. This is how you get the classic spring onion with the full white root end. Good for a larger harvest; requires replanting.

Harvest-ready checklist

• Tops 20–30 cm (8–12 in) tall
• White base 1 cm (½ in) or wider
• Leaves upright, not flopping
• No flower stalk visible (if one appears, harvest immediately)

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Common mistakes

• Planting seeds too deep. More than 1 cm (½ in) and germination drops sharply. Green onion seeds are tiny — they need light to reach the surface quickly.
• Overwatering kitchen-scrap stubs. The most common scrap-regrowth failure is changing water too infrequently or leaving the base sitting in 5 cm (2 in) of stagnant water. Change water every 1–2 days, or just go straight to soil.
• Expecting indefinite regrowth from scraps. Each cut weakens the stored energy. After 3–5 cuts, the base is spent. Sow new seeds rather than trying to extend a failing plant.
• Planting in shade. Green onions tolerate partial shade but they will not thrive with fewer than 4 hours of light. Pale, floppy tops are the result.
• Ignoring a flower stalk. Once a green onion bolts (sends up a flower), the base toughens and flavor turns sharp. Cut the flower off immediately and harvest the greens now — the plant won’t produce quality tops after bolting.
• Using garden soil in containers. Garden soil compacts in pots, chokes roots, and stays soggy. Use a quality potting mix for all container growing.

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Troubleshooting

Symptom	Likely cause	Fix
Seeds didn’t germinate after 2+ weeks	Soil crust sealed surface; soil too dry; temperature below 10°C (50°F)	Mist daily to break crust; move to warmer spot; resow shallower
Pale yellow tops, floppy growth	Not enough light	Move to a brighter location; 6+ hours daily
Brown, crispy tip on each leaf	Underwatering or low humidity	Water more frequently; avoid letting soil dry deep
Mushy white base, rotting smell	Overwatering or poor drainage	Reduce watering; check drainage holes; replant in fresh mix
Tops very thin, weak after kitchen-scrap regrowth	Bulb energy exhausted	Compost that plant; start fresh with new seeds or scraps
Flower stalk shooting up	Bolting from heat or stress	Cut flower off, harvest all greens now; replant for next batch
Tiny black flies around pot	Fungus gnats from staying too wet	Let soil dry more between waterings; add a 1 cm (½ in) dry sand top layer
Growth stopped in summer heat	Temperature above 27°C (80°F)	Move to partial shade; resume in early autumn when temperatures drop

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Watch: How to grow green onions

A visual walkthrough of the seed and kitchen-scrap methods pairs well with the steps above. After reading this guide, search YouTube for “how to grow green onions from scraps” or “scallion planting guide” for a side-by-side visual of the water-to-soil transplant technique.

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Related reading

• How to plant onion bulbs (sets) for full-size storage onions — if you want bulbing onions, that post covers long-day vs short-day varieties, 2.5 cm (1 in) depth, 10–15 cm (4–6 in) spacing, and the 90–120-day harvest timeline.
• How to plant onions that have already sprouted — a store-bought onion sprouting in your pantry is just another source of free green onion tops; this guide shows how to get them out of the compost bin and into a pot.
• How to plant asparagus crowns — another early-season edible for the same bed; asparagus and green onions are good garden neighbours.
• How to plant garlic cloves — garlic is a close relative; many gardeners rotate garlic and scallion beds each season.
• Track harvest intervals and set succession-planting reminders with the free Tazart plant care app.

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A note on conditions

Every garden and home grows differently. Soil mix, pot depth, light intensity, local temperature, and humidity all affect how fast your green onions grow and how often they need water. The depths, spacings, and timelines above are well-tested starting points — adjust them based on what your plants actually do in the first two weeks, and you’ll dial in a continuous supply quickly.