Seed Starting Calendar for Maine

Count back from the median last frost where you garden. At Bangor (Bangor Intl Airport) that date is May 4, so for spring 2027 onions start indoors Jan 26 to Feb 9, peppers Mar 9 to Mar 23 and tomatoes Mar 16 to Mar 30. Across Maine's 79 NOAA stations the median last frost runs from Apr 27 to May 25 for the middle 90 percent, so a garden near Allagash starts later than one near Woodland.

It depends on the station. The earliest median last spring freeze in Maine is April 21 at Woodland; the latest is June 2 at Allagash. A median is a coin flip: at Bangor the last 32°F freeze comes after May 4 in half of years, and has passed by May 17 in 9 of 10 years (NOAA 1991 to 2020 normals).

UNH Extension sets tomatoes out 1 to 2 weeks after the last frost, which at Bangor is May 11 to May 18 in 2027. Tomatoes are frost tender, so the date to watch is May 17, when 9 of 10 springs at Bangor have had their last 32°F night. Hardening off starts two weeks before setting out (Apr 27 to May 11).

University of Maine Cooperative Extension publishes planting months by region (Central Maine). For Central Maine, tomatoes go in during May and June. Seeds for transplants go in 4 to 10 weeks ahead of those months, depending on the crop.

University of Maine Cooperative Extension's Bulletin #2751, Starting Seeds at Home puts it this way: "Seedlings may take from 4 to 12 weeks; the amount of time will usually be indicated on the seed package. To determine when to start seeds indoors, count back from the average last spring frost date for your area." The guide is linked below with the date it was read (September 21, 2026).

UNH Extension gives 8 to 10 weeks from seed to transplant for both, and sets peppers out 2 weeks after the last frost and eggplant 2 to 3 weeks after, so the sowing date is 6 to 8 weeks before the median last frost. At Bangor that is Mar 9 to Mar 23 for peppers.

About two weeks. University of Missouri Extension: "Hardening should be started about two weeks before planting in the garden." University of Minnesota Extension adds that seedlings should go out on a cloudy day or in the late afternoon.

Portland on Casco Bay reaches its median last frost around Apr 26, Bangor around May 4, Caribou around May 7, and Houlton in Aroostook County not until about May 27. Each station carries its own dates: Portland Apr 26 and Houlton Intl Airport May 27 at the median.