All plants

Green Onion

Allium fistulosum

Amaryllidaceae · onion family

Matures
50–80 days
Harvest
Over a period · Annual
Sun
6–8+ hrs
Spacing
1–2 in
Botanical engraving of Green Onion

Planting window

When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.

JanFebMarAprMayJun
Foggy●◐◐◐
Sunny●●●●●
JulAugSepOctNovDec
Foggy◐◐●◐◐
Sunny◐●●●◐
Well-suitedMarginalNot suited

Sunlight

How well it does at each level of direct sun per day.

<2 hrsNot suited
2–4 hrsNot suited
4–6 hrsMarginal
6–8 hrsWell-suited
8+ hrsWell-suited
Well-suitedMarginalNot suited

Soil depth

Root room it needs — useful for sizing raised beds and containers.

6–10"Well-suited
10–15"Well-suited
15–18"Well-suited
18–24"Well-suited
Well-suitedMarginalNot suited

Spacing

Room each plant needs — along the row and between rows — for sizing beds.

In-row
1–2 in
Between rows
12 in

Growth habit

The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.

Habit
Upright
Mature height
12–18 in

Stands on its own; the tallest types appreciate a stake in wind.

How to start it

Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.

Usually
Direct-sow
Start indoors
5 weeks ahead
Direct-sowWell-suited
TransplantWell-suited

Sown straight into the bed it will grow in.

Well-suitedMarginalNot suited

Getting started

How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.

Started from
From seed
Ideal soil temp
65–85°F
Sow depth
0.25 in
Time to emerge
4–7 days

Germinates between 32–95°F; happiest around 65–85°F.

30°F110°F
IdealWorkable

Pests & diseases

What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.

Grown as, and troubled the same as, onions.

Pests2

Thrips
What it is
Most adult thrips are elongate, slender, minute (less than 1/20 inch long), and have long fringes on the margins of both pairs of their long, narrow wings. Immatures (called larvae or nymphs) are oblong or slender and elongate and lack wings.
What you'll see
Thrips feeding on plants can damage fruit, leaves, and shoots and very noticeably affect plants’ cosmetic appearance. However, thrips rarely kill or threaten the survival of trees and shrubs.
What to do
Thrips species that feed on many different plant species often move into gardens and landscapes when plants in weedy areas or grasslands begin to dry in spring or summer. Avoid planting susceptible plants next to these areas, and control nearby weeds that are alternate hosts of pest thrips.
Source
Onion Maggot
What you'll see
White worm that feeds on seedlings, roots or bulbs.
What to do
Use crop rotation, avoid excessive amounts of organic matter, and apply insecticides at planting if maggots have been a problem in the past. Destroy infected plants.
Source

Diseases3

Neck Rot
What you'll see
Fungal disease that occurs during storage. Watery decay inside the bulb.
What to do
Avoid excess moisture near harvest. Cure bulbs well before storing.
Source
Basal Rot
What you'll see
Fungal disease that attacks the area where roots and leaves join. The area rots and plant growth is slow and weak.
What to do
Use long crop rotations, solarize the soil where onions are planted, and avoid over-watering.
Source
Pink Root
What you'll see
Fungal disease that changes roots to a pink color. Roots eventually die and yields are severely reduced
What to do
Use long crop rotation and solarize the soil where onions are planted.
Source

Sources

Every figure above is backed by these.