When to plant summer squash / zucchini in Calgary
Summer squash / Zucchini is frost-tender, so every date keys off Calgary's last spring frost of May 22.
Step 1 · Sow
Start seeds indoors
May 27 – Jun 17
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Jul 18 – Aug 8
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Sep 1 – Sep 16
Picking runs until conditions turn against the crop.
Window
Days to maturity
45 – 60 d
Calgary's 120-day season leaves this much room.
Summer squash / Zucchini on Calgary'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 22
SEP 19
Common questions
When can I sow summer squash / zucchini outdoors in Calgary?
Direct-sow around mid July (Jul 18–Aug 8) in Calgary, based on its local frost dates. Confidence 80%.
When will summer squash / zucchini be ready to harvest in Calgary?
Expect to harvest from around early September (Sep 1–Sep 16) in Calgary, based on its local frost dates. Confidence 74%.
When should I start summer squash / zucchini seeds indoors in Calgary?
Start seeds indoors around late May (May 27–Jun 17) in Calgary, based on its local frost dates. Confidence 78%.
When can I transplant summer squash / zucchini outdoors in Calgary?
Transplant outdoors around mid July (Jul 18–Aug 8) in Calgary, based on its local frost dates. Confidence 80%.
How long is the growing season in Calgary?
Calgary has roughly 120 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 Calgary's frost dates.
Confidence 82/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.