When to plant onion in Tokyo
Onion is cold-hardy, so every date keys off Tokyo's frost dates of Mar 25.
Step 1 · Sow
Start seeds indoors
Jan 14 – Feb 4
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Mar 4 – Mar 25
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jun 2 – Jun 22
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Tokyo's 255-day season leaves this much room.
Onion on Tokyo'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
MAR 25
DEC 5
Common questions
When will onion be ready to harvest in Tokyo?
Expect to harvest from around early June (Jun 2–Jun 22) in Tokyo, based on its local frost dates. Confidence 79%.
When should I start onion seeds indoors in Tokyo?
Start seeds indoors around mid January (Jan 14–Feb 4) in Tokyo, based on its local frost dates. Confidence 84%.
When can I transplant onion outdoors in Tokyo?
Transplant outdoors around early March (Mar 4–Mar 25) in Tokyo, based on its local frost dates. Confidence 88%.
How long is the growing season in Tokyo?
Tokyo has roughly 255 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 Tokyo's frost dates.
Confidence 88/100 · NOAA GHCN-Daily · 1991–2020 normals · frost dates are probabilities, not guarantees.