When to plant onion in Colorado Springs
Onion is cold-hardy, so every date keys off Colorado Springs's frost dates of May 5.
Step 1 · Sow
Start seeds indoors
Feb 24 – Mar 17
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
May 8 – May 29
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Aug 6 – Aug 26
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Colorado Springs's 153-day season leaves this much room.
Onion on Colorado Springs'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 5
OCT 5
Common questions
When will onion be ready to harvest in Colorado Springs?
Expect to harvest from around early August (Aug 6–Aug 26) in Colorado Springs, based on its local frost dates. Confidence 79%.
When should I start onion seeds indoors in Colorado Springs?
Start seeds indoors around late February (Feb 24–Mar 17) in Colorado Springs, based on its local frost dates. Confidence 84%.
When can I transplant onion outdoors in Colorado Springs?
Transplant outdoors around early May (May 8–May 29) in Colorado Springs, based on its local frost dates. Confidence 85%.
How long is the growing season in Colorado Springs?
Colorado Springs has roughly 153 frost-free days, which is enough time to grow onion to maturity outdoors.
The rule of thumb
Sow onion 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 Colorado Springs's frost dates.
Confidence 88/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.