When to plant sweet potato in Washington
Sweet potato is frost-tender, so every date keys off Washington's last spring frost of Mar 24.
Step 1 · Plant
Transplant outdoors
May 13 – Jun 3
Once frost risk has passed and nights stay mild.
Step 2 · Harvest
Harvest window
Aug 11 – Sep 10
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 120 d
Washington's 234-day season leaves this much room.
Sweet potato on Washington'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 24
NOV 17
Common questions
When will sweet potato be ready to harvest in Washington?
Expect to harvest from around mid August (Aug 11–Sep 10) in Washington, based on its local frost dates. Confidence 80%.
When can I transplant sweet potato outdoors in Washington?
Transplant outdoors around mid May (May 13–Jun 3) in Washington, based on its local frost dates. Confidence 86%.
How long is the growing season in Washington?
Washington has roughly 234 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 Washington's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.