When to plant potatoes in zone 3a

The zone 3a schedule for potatoes

Sow outdoors

May 15 to 22

Soil warm enough (50°F), about

May 15

First harvest, roughly

August 8 to September 19

From the median frost dates of the NOAA stations assigned to the 8 ZIP codes in zone 3a, and the timing recommended by Cooperative Extension guides for potatoes.

Dates before the last frost assume the soil has thawed and is dry enough to work: a squeezed handful crumbles instead of sticking. After a late or wet spring, wait for that even if the date has passed.

Frost risk in zone 3a

Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 3a, the typical last frost ranges from about May 10 in the earliest tenth of ZIP codes to June 2 in the latest tenth, and the first fall frost from September 12 to October 1. For a typical place in the zone:

• May 10Risky: a later frost happens in 9 years out of 10
• May 26Typical: frost after this date in half of years
• June 11Safe: a later frost only 1 year in 10