When to plant sweet corn in Portland
Sweet corn is frost-tender, so every date keys off Portland's last spring frost of May 1.
Step 1 · Sow
Direct sow outdoors
Jun 11 – Jul 2
Sow straight into warm, workable soil.
Step 2 · Harvest
Harvest window
Aug 10 – Sep 19
Picking runs until conditions turn against the crop.
Window
Days to maturity
60 – 100 d
Portland's 165-day season leaves this much room.
Sweet corn on Portland'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
HARVEST
MAY 1
OCT 10
Common questions
When can I sow sweet corn outdoors in Portland?
Direct-sow around mid June (Jun 11–Jul 2) in Portland, based on its local frost dates. Confidence 86%.
When will sweet corn be ready to harvest in Portland?
Expect to harvest from around early August (Aug 10–Sep 19) in Portland, based on its local frost dates. Confidence 80%.
How long is the growing season in Portland?
Portland has roughly 165 frost-free days, which is enough time to grow sweet corn to maturity outdoors.
The rule of thumb
Sow sweet corn 6–8 weeks before your last spring frost; plant out 2–3 weeks after it. Every date on this page is derived from that rule and Portland's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.