When to plant sweet potato in Portland
Sweet potato is frost-tender, so every date keys off Portland's last spring frost of Mar 1.
Step 1 · Plant
Transplant outdoors
Jul 3 – Jul 24
Once frost risk has passed and nights stay mild.
Step 2 · Harvest
Harvest window
Oct 1 – Oct 31
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 120 d
Portland's 266-day season leaves this much room.
Sweet potato 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
MAR 1
NOV 22
Common questions
When will sweet potato be ready to harvest in Portland?
Expect to harvest from around early October (Oct 1–Oct 31) in Portland, based on its local frost dates. Confidence 79%.
When can I transplant sweet potato outdoors in Portland?
Transplant outdoors around early July (Jul 3–Jul 24) in Portland, based on its local frost dates. Confidence 85%.
How long is the growing season in Portland?
Portland has roughly 266 frost-free days, which is enough time to grow sweet potato to maturity outdoors.
The rule of thumb
Sow sweet potato 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 88/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.