When to plant sweet potato in Portland
Sweet potato is frost-tender, so every date keys off Portland's last spring frost of May 1.
Step 1 · Plant
Transplant outdoors
Jun 28 – Jul 19
Once frost risk has passed and nights stay mild.
Step 2 · Harvest
Harvest window
Sep 26 – Oct 26
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 120 d
Portland's 165-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
MAY 1
OCT 10
Common questions
When will sweet potato be ready to harvest in Portland?
Expect to harvest from around late September (Sep 26–Oct 26) in Portland, based on its local frost dates. Confidence 80%.
When can I transplant sweet potato outdoors in Portland?
Transplant outdoors around late June (Jun 28–Jul 19) in Portland, based on its local frost dates. Confidence 86%.
How long is the growing season in Portland?
Portland has roughly 165 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 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.