When to plant onion in Durham
Onion is cold-hardy, so every date keys off Durham's frost dates of Apr 2.
Step 1 · Sow
Start seeds indoors
Jan 22 – Feb 12
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Mar 18 – Apr 8
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jun 16 – Jul 6
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Durham's 218-day season leaves this much room.
Onion on Durham'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 2
NOV 1
Common questions
When will onion be ready to harvest in Durham?
Expect to harvest from around mid June (Jun 16–Jul 6) in Durham, based on its local frost dates. Confidence 75%.
When should I start onion seeds indoors in Durham?
Start seeds indoors around late January (Jan 22–Feb 12) in Durham, based on its local frost dates. Confidence 79%.
When can I transplant onion outdoors in Durham?
Transplant outdoors around mid March (Mar 18–Apr 8) in Durham, based on its local frost dates. Confidence 81%.
How long is the growing season in Durham?
Durham has roughly 218 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 Durham's frost dates.
Confidence 83/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.