How to Grow Green Onions from Seed: A Complete Guide
Green onions (Allium fistulosum), also called bunching onions or scallions, are one of the most dependable crops you can grow from seed. They are frost hardy, take up very little space, and give you mild, fresh onion flavor for months at a time. Starting your own seeds also lets you choose from far more varieties than you will find at the store. With an early spring start and a new sowing every couple of weeks, you can keep green onions coming from late summer onward. [Shop green onion seeds]
Green onion growing at a glance
- Botanical name: Allium fistulosum
- Need for sun: 6–12 hours
- Planting depth: 1/4″
- Sprouts in: 7–10 days
- Ideal growing temperature: 50–80°F
- Plant spacing: 4–6″
- Frost hardy: Yes
- Growth habit: Upward, compact growth
When to Start Green Onion Seeds
Start green onion seeds in a seedling tray in early spring, then transplant them outdoors for a late summer harvest. Because green onions are frost hardy, they can go into the garden earlier than tender crops like peppers and tomatoes.
Your climate decides how long your sowing season lasts. In a mild climate, cold-hardy green onions can also be seeded in fall and overwintered for an early harvest the following year. In a cold climate, sow green onions only in spring and summer.
How to Start Green Onion Seeds in Seedling Trays
- Fill a seedling tray with a light, moist seed starting mix.
- Sow seeds 1/4″ deep and cover them with mix.
- Keep the soil evenly moist. Seeds should sprout in 7–10 days.
- Give the seedlings good light so they grow into sturdy, upright shoots.
When to Transplant Green Onions
Transplant seedlings into the garden in early spring. Green onions grow best at 50–80°F and are frost hardy, so cool spring weather suits them well.
Best Soil and Spacing for Green Onions
Plant green onions in compost-rich soil in a spot that gets 6–12 hours of sun a day. Space plants 4–6″ apart. Green onions have an upward, compact growth habit, so they fit easily into small beds, borders and containers.
How to Fertilize Green Onions
Incorporate potassium into the growing area for better plant growth. Working compost into the bed before planting also gives green onions a steady supply of nutrients through the season.
How to Water Green Onions
Water regularly, especially during dry spells. Green onions have shallow roots, so steady moisture keeps the stalks tender and mild.
Keep the Bed Weed Free
Keep the planting area weed free to maximize yield. Green onions grow slim and upright and don’t shade out weeds, so weeds can easily crowd them and compete for water and nutrients. Weed gently by hand to avoid disturbing their shallow roots.
Succession Sowing for Continuous Harvests
Instead of planting all your green onions at once, keep sowing every two weeks. Each new tray of seedlings will be ready as the previous planting is harvested, giving you a steady supply instead of one large harvest all at once.
How to Harvest Green Onions
Harvest green onions once the stalks are about pencil thick. Pull whole plants as you need them, or cut the leaves about 1″ above the soil and let them grow back for another harvest.
Green Onion Growing FAQ
How long do green onion seeds take to germinate?
Green onion seeds sprout in about 7–10 days when the soil is kept moist.
How deep should I plant green onion seeds?
Plant green onion seeds about 1/4″ deep.
How far apart should green onion plants be?
Space green onion plants about 4–6″ apart.
How much sun do green onions need?
Green onions need 6–12 hours of sun a day.
When should I plant green onions?
Sow green onions in a seedling tray to transplant in early spring for a late summer harvest. In a mild climate, you can also sow them in fall to overwinter. In a cold climate, sow only in spring and summer.
Are green onions frost hardy?
Yes. Green onions are frost hardy, and in a mild climate, cold-hardy green onions can be overwintered in the garden.
How do I get a continuous harvest of green onions?
Keep sowing every two weeks. Each new planting will be ready as the previous one is harvested.
What fertilizer is best for green onions?
Incorporate potassium into the growing area for better plant growth, and plant in compost-rich soil.