When to plant onion in Des Moines
Onion is cold-hardy, so every date keys off Des Moines's frost dates of Apr 17.
Step 1 · Sow
Start seeds indoors
Feb 6 – Feb 27
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 16 – May 7
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 15 – Aug 4
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Des Moines's 179-day season leaves this much room.
Onion on Des Moines'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 17
OCT 16
Common questions
When will onion be ready to harvest in Des Moines?
Expect to harvest from around mid July (Jul 15–Aug 4) in Des Moines, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Des Moines?
Start seeds indoors around early February (Feb 6–Feb 27) in Des Moines, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Des Moines?
Transplant outdoors around mid April (Apr 16–May 7) in Des Moines, based on its local frost dates. Confidence 86%.
How long is the growing season in Des Moines?
Des Moines has roughly 179 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 Des Moines's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.