When to plant onion in Sioux Falls
Onion is cold-hardy, so every date keys off Sioux Falls's frost dates of May 1.
Step 1 · Sow
Start seeds indoors
Feb 20 – Mar 13
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
May 3 – May 24
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Aug 1 – Aug 21
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Sioux Falls's 153-day season leaves this much room.
Onion on Sioux Falls'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 1
OCT 2
Common questions
When will onion be ready to harvest in Sioux Falls?
Expect to harvest from around early August (Aug 1–Aug 21) in Sioux Falls, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Sioux Falls?
Start seeds indoors around mid February (Feb 20–Mar 13) in Sioux Falls, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Sioux Falls?
Transplant outdoors around early May (May 3–May 24) in Sioux Falls, based on its local frost dates. Confidence 86%.
How long is the growing season in Sioux Falls?
Sioux Falls 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 Sioux Falls's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.