When to plant onion in Rochester
Onion is cold-hardy, so every date keys off Rochester's frost dates of Apr 29.
Step 1 · Sow
Start seeds indoors
Feb 18 – Mar 11
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 30 – May 21
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 29 – Aug 18
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Rochester's 173-day season leaves this much room.
Onion on Rochester'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 29
OCT 24
Common questions
When will onion be ready to harvest in Rochester?
Expect to harvest from around late July (Jul 29–Aug 18) in Rochester, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Rochester?
Start seeds indoors around mid February (Feb 18–Mar 11) in Rochester, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Rochester?
Transplant outdoors around late April (Apr 30–May 21) in Rochester, based on its local frost dates. Confidence 86%.
How long is the growing season in Rochester?
Rochester has roughly 173 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 Rochester's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.