Scallion
Allium fistulosum
also called spring onion, green onion, salad onion
Slim, quick allium that masks carrots and tucks between slower crops.
- Type
- Vegetable · Grown as an annual
- Botanical family
- Allium (onion family)
- Foliage color
- Green
- Sunlight
- Full sun
- Watering
- Moderate
- Soil
- Fertile, well-drained
- Feeding
- Bulbs & roots
- Frost tolerant
- Yes
- Cool-season crop
- Yes — takes a second fall window
- Season
- Cool Season
- Harvest type
- Single Harvest
- Start from
- seed
- Germination temp
- 50–77°F
- Min soil temp
- 41 °F
- Photoperiod
- day neutral
- Sow direct
- 21 days before the last spring frost
- First harvest
- 60 days after the last spring frost
- Harvest ends
- at the first fall frost
- 0 d Sow seeds
- 10 d Germination
- 50 d Harvest
- Plant spacing
- 1.6 in
- In-row spacing
- 1.2 in
- Between rows
- 5.9 in
- Square-foot density
- 16 per square
- Sow depth
- 0.4 in
- Root system
- Fine and fibrous, close to the surface
- Working depth
- 6–12 in
- Can reach
- 18 in down where the soil allows
- Spread
- 2–3 in across, about 1–1.5× the width of the plant
- Shallowest pot
- 8 in of soil
The whole root system sits in the top hand-span of soil, so this is the first thing in the bed to feel a dry week and the last thing that should meet a fork. Hoe shallowly around it, and mulch instead of digging.
The habit is Scallion’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- Cats and dogs
- Recorded toxic
Recorded as toxic to cats and dogs by Pet Poison Helpline.
The Pet Poison Helpline Onions page names the genus Allium and lists Green Onions, which is this plant under one of our own alternate names, and it names both dogs and cats. Cornell names only cattle, horses and children, and the ASPCA has no Allium fistulosum row.
- When
- Ready 8–10 weeks from sowing in warm weather, longer for autumn sowings that overwinter and crop in spring. Successional sowings every 2–3 weeks from early spring to late summer give a near-continuous supply.
- What to look for
- Stems pencil-thick (6–15 mm), 15–20 cm of green top, with a white shank and no appreciable bulbing for classic salad onions. Thicker is fine — they just get stronger-flavored and can be used like baby leeks.
- How to harvest
- Water the row first if dry, then pull straight up holding the base of the stems, or ease with a hand fork in compacted soil to avoid snapping the shank. Pull the largest first, thinning as you go, so neighbors have room to size up.
- How often
- Harvest by progressive thinning over 3–4 weeks per sowing; the crop stands quite well but eventually bulbs or bolts. Rely on succession sowing rather than one long-standing row for continuity.
- Storing the crop
- Keep 1–2 weeks in the fridge in a perforated bag, or stand them upright in a jar with 2 cm of water (roots down), covered loosely, where they stay crisp and even regrow. Sliced green tops freeze well straight into bags for cooking.
- Onion fly & leek moth Maggots burrow into the base of onions, leeks, and garlic; leaves yellow and droop. Grow alliums under insect mesh and rotate to fresh ground each year.
- Thrips Minute slender insects that leave silvery flecking and distortion on leaves and flowers in hot, dry spells. Keep plants watered and use blue sticky traps under glass.
- Root & crown rot Roots or crown turn brown and mushy in waterlogged soil or compost; the plant wilts even when wet. Improve drainage, water less, and pot up only into free-draining mixes.
- Rust Orange-brown powdery pustules on leaf undersides, weakening the plant over the season. Remove affected leaves, avoid overhead watering, and clear all debris in autumn.
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Beneficial nematodes Steinernema & Heterorhabditis spp.Hunts Onion fly & leek moth
Microscopic worms watered onto damp soil that hunt down soil-dwelling grubs and release a bacterium that kills them within days. Timing is the whole thing: warm, damp soil and a small target grub, which means late summer for most of what they are used against.
- Big-eyed bug Geocoris spp.Hunts Thrips
A stubby 3 mm bug with enormous wrap-around eyes, working the soil surface and the low foliage for aphids, mites, thrips and insect eggs. It is the main natural check on chinch bugs in a lawn and it is killed outright by insecticide.
- Damsel bug NabidaeHunts Thrips
A slender, mantis-armed bug that grabs aphids, small caterpillars, and thrips in low crops and meadowy edges. Leave a strip of unmown grasses and flowers for it to overwinter in.
- Green lacewing Chrysoperla carneaHunts Thrips
Its bristly larvae — "aphid lions" — impale aphids, mealybugs, thrips, and mite colonies, eating hundreds a week. Adults feed on nectar and pollen from small open flowers and overwinter in hollow stems left standing.
- Hoverfly SyrphidaeHunts Thrips
Bee-mimicking flies whose legless larvae graze aphid colonies clean while the adults pollinate. A ribbon of shallow, nectar-rich flowers kept in bloom all season recruits wave after wave of them.
- Minute pirate bug Orius spp.Hunts Thrips
A pinhead-sized true bug that is the best natural check on thrips, and happily spears aphids, mites, and insect eggs too. It needs pollen when prey is scarce, so keep something flowering nearby.
- Predatory mites Phytoseiulus & AmblyseiusHunts Thrips
Fast orange mites that hunt spider mites egg-by-egg, and cousins that clear thrips and fungus-gnat larvae. Sold as a biological control for greenhouses; outdoors they follow humidity — mist and mulch, don’t dust with sulfur.
- Rove beetle StaphylinidaeHunts Onion fly & leek moth
Slim, quick beetles with short wing cases that hunt in soil and litter, taking root-fly eggs and larvae, fungus-gnat larvae, and mites. Mulch and undisturbed ground keep them resident year-round.
Good neighbors
Keep apart
Quick and forgiving — sow a short row every few weeks for a steady supply.
Green-leaved vegetables, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com