When to plant onion in Salt Lake City
Onion is cold-hardy, so every date keys off Salt Lake City's frost dates of Apr 13.
Step 1 · Sow
Start seeds indoors
Feb 2 – Feb 23
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 15 – May 6
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 14 – Aug 3
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Salt Lake City's 194-day season leaves this much room.
Onion on Salt Lake City'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
APR 13
OCT 26
Common questions
When will onion be ready to harvest in Salt Lake City?
Expect to harvest from around mid July (Jul 14–Aug 3) in Salt Lake City, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Salt Lake City?
Start seeds indoors around early February (Feb 2–Feb 23) in Salt Lake City, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Salt Lake City?
Transplant outdoors around mid April (Apr 15–May 6) in Salt Lake City, based on its local frost dates. Confidence 86%.
How long is the growing season in Salt Lake City?
Salt Lake City has roughly 194 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 Salt Lake City's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.