When to plant onion in Frankfurt
Onion is cold-hardy, so every date keys off Frankfurt's frost dates of Mar 30.
Step 1 · Sow
Start seeds indoors
Jan 19 – Feb 9
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 10 – May 1
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 9 – Jul 29
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Frankfurt's 230-day season leaves this much room.
Onion on Frankfurt'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 30
NOV 15
Common questions
When will onion be ready to harvest in Frankfurt?
Expect to harvest from around early July (Jul 9–Jul 29) in Frankfurt, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Frankfurt?
Start seeds indoors around mid January (Jan 19–Feb 9) in Frankfurt, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Frankfurt?
Transplant outdoors around early April (Apr 10–May 1) in Frankfurt, based on its local frost dates. Confidence 86%.
How long is the growing season in Frankfurt?
Frankfurt has roughly 230 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 Frankfurt's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.