When to plant summer squash / zucchini in Denver
Summer squash / Zucchini is frost-tender, so every date keys off Denver's last spring frost of May 4.
Step 1 · Sow
Start seeds indoors
May 7 – May 28
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Jun 1 – Jun 22
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 16 – Jul 31
Picking runs until conditions turn against the crop.
Window
Days to maturity
45 – 60 d
Denver's 157-day season leaves this much room.
Summer squash / Zucchini on Denver'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
MAY 4
OCT 10
Common questions
When can I sow summer squash / zucchini outdoors in Denver?
Direct-sow around early June (Jun 1–Jun 22) in Denver, based on its local frost dates. Confidence 82%.
When will summer squash / zucchini be ready to harvest in Denver?
Expect to harvest from around mid July (Jul 16–Jul 31) in Denver, based on its local frost dates. Confidence 76%.
When should I start summer squash / zucchini seeds indoors in Denver?
Start seeds indoors around early May (May 7–May 28) in Denver, based on its local frost dates. Confidence 81%.
When can I transplant summer squash / zucchini outdoors in Denver?
Transplant outdoors around early June (Jun 1–Jun 22) in Denver, based on its local frost dates. Confidence 82%.
How long is the growing season in Denver?
Denver has roughly 157 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 Denver's frost dates.
Confidence 85/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.