When to plant onion in Edinburgh
Onion is cold-hardy, so every date keys off Edinburgh's frost dates of Apr 18.
Step 1 · Sow
Start seeds indoors
Feb 7 – Feb 28
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
May 14 – Jun 4
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Aug 12 – Sep 1
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Edinburgh's 201-day season leaves this much room.
Onion on Edinburgh'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
FROST
APR 18
OCT 30
Common questions
When will onion be ready to harvest in Edinburgh?
Expect to harvest from around mid August (Aug 12–Sep 1) in Edinburgh, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Edinburgh?
Start seeds indoors around early February (Feb 7–Feb 28) in Edinburgh, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Edinburgh?
Transplant outdoors around mid May (May 14–Jun 4) in Edinburgh, based on its local frost dates. Confidence 86%.
How long is the growing season in Edinburgh?
Edinburgh has roughly 201 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 Edinburgh's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.