When to plant broccoli in Denver
Broccoli is cold-hardy, so every date keys off Denver's frost dates of May 4.
Step 1 · Sow
Start seeds indoors
Mar 23 – Apr 13
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 20 – May 11
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jun 19 – Jul 14
Picking runs until conditions turn against the crop.
Step 4 · Second sowing
Autumn / second sowing
Jun 26 – Jul 10
A second window for a fall crop, timed to mature before the first frost.
Step 5 · Second harvest
Autumn crop harvest
Sep 1 – Sep 26
Maturity window for the second sowing.
Window
Days to maturity
60 – 85 d
Denver's 157-day season leaves this much room.
Broccoli 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 will broccoli be ready to harvest in Denver?
Expect to harvest from around mid June (Jun 19–Jul 14) in Denver, based on its local frost dates. Confidence 76%.
When should I start broccoli seeds indoors in Denver?
Start seeds indoors around late March (Mar 23–Apr 13) in Denver, based on its local frost dates. Confidence 81%.
When can I transplant broccoli outdoors in Denver?
Transplant outdoors around mid April (Apr 20–May 11) in Denver, based on its local frost dates. Confidence 85%.
Can I plant broccoli in autumn in Denver?
Yes — Denver supports a second, autumn sowing of broccoli around late June (Jun 26–Jul 10), 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 broccoli to maturity outdoors.
The rule of thumb
Sow broccoli 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.