Scallion (Allium fistulosum), the bunching or Welsh onion, is a perennial onion that forms no true bulb; its hollow green leaves are cut for the kitchen, and the seed has an optimum germination range of 13–20 °C.

Also known as: Welsh onion, Bunching onion, Japanese bunching onion, Spring onion, Green onion, Hara pyaz, Negi (Japanese), Ciboule (French), Winterzwiebel, Luk-batun, Bawang daun (Indonesian), Hanh hoa (Vietnamese).

Scallion or common onion?

Scallion does not develop a bulb, and its leaves and flower stalks are hollow, which gives the species its name (fistulosum, “hollow”). It has no long-day dormant stage like the common onion (Allium cepa), though the two taste and smell alike and can hybridise. This lot is sold as “white flower”; we state no further cultivar traits.

What the seed tells you

• Seed is black, about 3–4 mm long.
• 1,000 seeds weigh about 2.4–3.4 g, roughly 290–420 seeds per gram (typical for the species, varies by lot).
• Seed kept at room temperature loses germination capacity and vigour after about 12 months, so sow it fresh.
• Optimum germination temperature is 13–20 °C (approximate, species level).

Growing steps

1. Sow thinly in a cool spot, where the mix stays within 13–20 °C.
2. Keep the mix evenly moist and move seedlings into stronger light gradually.
3. Transplant when seedlings are about 25–30 cm tall and roughly pencil-thick, at about 20 × 25 cm spacing.
4. Cut leaves green, or pull whole plants.

Limits

In hot lowland climates, scallion is usually propagated from basal tillers rather than seed, so seed sowing suits cooler seasons. Hot, humid conditions are tolerated once plants are established.

FAQ

Will it bolt?

Flowering is generally induced below 13 °C once the seedling has enough leaves or a thick enough pseudostem. In cold-adapted cultivars, short days can also stop growth and cause leaves to die back.

Can I keep a clump going without resowing?

Yes. It is a perennial that spreads by forming evergreen clumps, and home gardeners often keep it as one, dividing basal tillers.