When to plant spinach in Denver
Spinach is cold-hardy, so every date keys off Denver's frost dates of May 4.
Step 1 · Sow
Direct sow outdoors
Mar 23 – Apr 13
Sow straight into warm, workable soil.
Step 2 · Harvest
Harvest window
May 2 – May 12
Picking runs until conditions turn against the crop.
Step 3 · Second sowing
Autumn / second sowing
Jul 31 – Aug 14
A second window for a fall crop, timed to mature before the first frost.
Step 4 · Second harvest
Autumn crop harvest
Sep 16 – Sep 26
Maturity window for the second sowing.
Window
Days to maturity
40 – 50 d
Denver's 157-day season leaves this much room.
Spinach 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 spinach outdoors in Denver?
Direct-sow around late March (Mar 23–Apr 13) in Denver, based on its local frost dates. Confidence 85%.
When will spinach be ready to harvest in Denver?
Expect to harvest from around early May (May 2–May 12) in Denver, based on its local frost dates. Confidence 76%.
Can I plant spinach in autumn in Denver?
Yes — Denver supports a second, autumn sowing of spinach around late July (Jul 31–Aug 14), timed to mature before the first fall frost.
How long is the growing season in Denver?
Denver has roughly 157 frost-free days, which is enough time to grow spinach to maturity outdoors.
The rule of thumb
Sow spinach 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 Denver's frost dates.
Confidence 85/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.