When to plant onion in Arlington
Onion is cold-hardy, so every date keys off Arlington's frost dates of Mar 6.
Step 1 · Sow
Start seeds indoors
Dec 26 – Jan 16
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Feb 25 – Mar 18
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
May 26 – Jun 15
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Arlington's 266-day season leaves this much room.
Onion on Arlington'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
MAR 6
NOV 23
Common questions
When will onion be ready to harvest in Arlington?
Expect to harvest from around late May (May 26–Jun 15) in Arlington, based on its local frost dates. Confidence 76%.
When should I start onion seeds indoors in Arlington?
Start seeds indoors around late December (Dec 26–Jan 16) in Arlington, based on its local frost dates. Confidence 80%.
When can I transplant onion outdoors in Arlington?
Transplant outdoors around late February (Feb 25–Mar 18) in Arlington, based on its local frost dates. Confidence 81%.
How long is the growing season in Arlington?
Arlington has roughly 266 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 Arlington's frost dates.
Confidence 84/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.