When to plant onion in Kansas City
Onion is cold-hardy, so every date keys off Kansas City's frost dates of Apr 3.
Step 1 · Sow
Start seeds indoors
Jan 23 – Feb 13
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 6 – Apr 27
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 5 – Jul 25
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Kansas City's 212-day season leaves this much room.
Onion on Kansas City'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 3
OCT 30
Common questions
When will onion be ready to harvest in Kansas City?
Expect to harvest from around early July (Jul 5–Jul 25) in Kansas City, based on its local frost dates. Confidence 78%.
When should I start onion seeds indoors in Kansas City?
Start seeds indoors around late January (Jan 23–Feb 13) in Kansas City, based on its local frost dates. Confidence 83%.
When can I transplant onion outdoors in Kansas City?
Transplant outdoors around early April (Apr 6–Apr 27) in Kansas City, based on its local frost dates. Confidence 84%.
How long is the growing season in Kansas City?
Kansas City has roughly 212 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 Kansas City's frost dates.
Confidence 87/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.