When to plant basil in St. Louis
Basil is frost-tender, so every date keys off St. Louis's last spring frost of Mar 30.
Step 1 · Sow
Start seeds indoors
Mar 6 – Mar 27
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 28 – Jul 28
Picking runs until conditions turn against the crop.
Window
Days to maturity
60 – 90 d
St. Louis's 218-day season leaves this much room.
Basil 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 basil 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 basil be ready to harvest in St. Louis?
Expect to harvest from around late June (Jun 28–Jul 28) in St. Louis, based on its local frost dates. Confidence 76%.
When should I start basil seeds indoors in St. Louis?
Start seeds indoors around early March (Mar 6–Mar 27) in St. Louis, based on its local frost dates. Confidence 80%.
When can I transplant basil 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 basil to maturity outdoors.
The rule of thumb
Sow basil 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.