When to plant summer squash / zucchini in St. Louis
Summer squash / Zucchini is frost-tender, so every date keys off St. Louis's last spring frost of Mar 30.
Step 1 · Sow
Start seeds indoors
Mar 27 – Apr 17
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 29 – May 20
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jun 13 – Jun 28
Picking runs until conditions turn against the crop.
Window
Days to maturity
45 – 60 d
St. Louis's 218-day season leaves this much room.
Summer squash / Zucchini on St. Louis'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 5
Common questions
When can I sow summer squash / zucchini outdoors in St. Louis?
Direct-sow around late April (Apr 29–May 20) in St. Louis, based on its local frost dates. Confidence 81%.
When will summer squash / zucchini be ready to harvest in St. Louis?
Expect to harvest from around mid June (Jun 13–Jun 28) in St. Louis, based on its local frost dates. Confidence 76%.
When should I start summer squash / zucchini seeds indoors in St. Louis?
Start seeds indoors around late March (Mar 27–Apr 17) in St. Louis, based on its local frost dates. Confidence 80%.
When can I transplant summer squash / zucchini outdoors in St. Louis?
Transplant outdoors around late April (Apr 29–May 20) in St. Louis, based on its local frost dates. Confidence 81%.
How long is the growing season in St. Louis?
St. Louis has roughly 218 frost-free days, which is enough time to grow summer squash / zucchini to maturity outdoors.
The rule of thumb
Sow summer squash / zucchini 6–8 weeks before your last spring frost; plant out 2–3 weeks after it. Every date on this page is derived from that rule and St. Louis's frost dates.
Confidence 84/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.