When to plant onion in Wilmington
Onion is cold-hardy, so every date keys off Wilmington's frost dates of Apr 6.
Step 1 · Sow
Start seeds indoors
Jan 26 – Feb 16
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 14 – May 5
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 13 – Aug 2
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Wilmington's 214-day season leaves this much room.
Onion on Wilmington'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 6
NOV 8
Common questions
When will onion be ready to harvest in Wilmington?
Expect to harvest from around mid July (Jul 13–Aug 2) in Wilmington, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Wilmington?
Start seeds indoors around late January (Jan 26–Feb 16) in Wilmington, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Wilmington?
Transplant outdoors around mid April (Apr 14–May 5) in Wilmington, based on its local frost dates. Confidence 86%.
How long is the growing season in Wilmington?
Wilmington has roughly 214 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 Wilmington's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.