Green onion
Allium fistulosum
Also known as: Scallion, Spring onion, Salad onion, Bunching onion, Negi, Cebollin
Quick facts
- Category
- roots bulbs
- Difficulty
- beginner
- Days to harvest
- 50 to 80 days
- Harvest type
- continuous production over weeks or months
- Spacing
- 5 cm between plants
Environment
- Temperature
- 10–25°C
- pH
- 6 to 7
- EC (hydroponic)
- 1.4 to 2 mS/cm
- Daily light
- 12 to 18 mol/m²/day
Climate and zones
- USDA zones
- 3 to 10 (winter low around -40°C or warmer)
- Frost tolerance
- very hardy (survives deep cold)
- Season
- cool (spring and fall crops)
Viable growing environments:
- outdoor year-round (in zone)
- outdoor in growing season (annual)
- unheated greenhouse / hoop house
- heated greenhouse
- indoor (heated home)
- indoor hydroponics under grow lights
USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.
Growing systems
Green onion works in:
- deep water culture (rafts)
- NFT channels
- media bed (ebb and flow)
- wicking bed
- soil bed
Growing media
The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (green onion works in the media listed below).
| Medium | pH effect | Water retention | Bacterial surface |
|---|---|---|---|
| Soil-based mix (Potting soil) | varies by source | high | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Net pot, no medium (Bare-root) | - | - | - |
Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.
Nutrient demand by stage
NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.
| Stage | N | P | K | EC target (mS/cm) |
|---|---|---|---|---|
| seedling | 1 | 1 | 1 | 0.8 |
| vegetative | 2 | 1 | 2 | 1.6 |
Aquaponics suitability
Compatible with typical aquaponics nutrient profiles. Fish waste provides enough nitrogen for healthy growth; supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.
Care notes
One of the easiest and fastest hydroponic crops. EC 1.0-2.0 mS/cm. pH 6.0-7.0. Temperature: 15–25°C (cool to moderate; tolerates a wide range). Moderate light (DLI 12-18 mol/m2/day). From seed to harvest: 6-8 weeks. From sets or bases: 2-3 weeks for usable greens. NFT, DWC, raft, Kratky, and vertical systems all work. The simplest hydroponic project: place store-bought green onion bases (with root nubs intact) in a jar of water on a windowsill; they regrow harvestable greens in 7-10 days. For continuous production, succession plant every 2 weeks. A. fistulosum varieties are perennial and regrow after cutting, providing indefinite harvests from a single planting. Harvest by cutting the green tops 3–5 cm above the base; the plant regrows from the center. For whole-plant harvest (white base and green top), pull the entire plant. Green onions are a staple crop for commercial hydroponic operations: fast turnover, consistent demand, good retail pricing ($2-4/bunch), and minimal pest or disease issues.
Verified against: rhs-uk. Last reviewed 2026-05-15.