When to plant onion in Auckland
Onion is cold-hardy, so every date keys off Auckland's frost dates of Aug 20.
Step 1 · Sow
Start seeds indoors
Jun 11 – Jul 2
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Jul 30 – Aug 20
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Oct 28 – Nov 17
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Auckland's 294-day season leaves this much room.
Onion on Auckland's growing year
Frost-bounded season with crops mapped onto the 12-month axis.
Frost risk Growing Harvest
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
FROST
AUG 20
JUN 10
Common questions
When will onion be ready to harvest in Auckland?
Expect to harvest from around late October (Oct 28–Nov 17) in Auckland, based on its local frost dates. Confidence 74%.
When should I start onion seeds indoors in Auckland?
Start seeds indoors around mid June (Jun 11–Jul 2) in Auckland, based on its local frost dates. Confidence 78%.
When can I transplant onion outdoors in Auckland?
Transplant outdoors around late July (Jul 30–Aug 20) in Auckland, based on its local frost dates. Confidence 82%.
How long is the growing season in Auckland?
Auckland has roughly 294 frost-free days, which is enough time to grow onion to maturity outdoors.
The rule of thumb
Sow onion as soon as the soil is workable — it tolerates cool weather and light frost. Every date on this page is derived from that rule and Auckland's frost dates.
Confidence 82/100 · NOAA GHCN-Daily · 1991–2020 normals · frost dates are probabilities, not guarantees.