Seed Starting Calendar for New Jersey

Count back from the median last frost where you garden. At Trenton (Trenton Mercer County Airport) that date is April 10, so for spring 2027 onions start indoors Jan 2 to Jan 16, peppers Feb 13 to Feb 27 and tomatoes Feb 20 to Mar 6. Across New Jersey's 46 NOAA stations the median last frost runs from Apr 1 to Apr 30 for the middle 90 percent, so a garden near Sussex Airport starts later than one near Margate.

It depends on the station. The earliest median last spring freeze in New Jersey is March 26 at Margate; the latest is May 1 at Sussex Airport. A median is a coin flip: at Trenton the last 32°F freeze comes after April 10 in half of years, and has passed by April 25 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 Trenton is Apr 17 to Apr 24 in 2027. Tomatoes are frost tender, so the date to watch is April 25, when 9 of 10 springs at Trenton have had their last 32°F night. Hardening off starts two weeks before setting out (Apr 3 to Apr 17).

Rutgers Cooperative Extension, New Jersey Agricultural Experiment Station (NJAES) publishes planting months by region (New Jersey). For New Jersey, tomatoes go in during May and June. Seeds for transplants go in 4 to 10 weeks ahead of those months, depending on the crop.

Rutgers Cooperative Extension, New Jersey Agricultural Experiment Station (NJAES)'s Planning a Vegetable Garden puts it this way: "Consider planning for spring planting of early crops and later plantings for late summer and autumn harvest. Use the table included in this fact sheet to help you plan." 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 Trenton that is Feb 13 to Feb 27 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.

Atlantic City reaches its median last frost around Mar 26, Newark around Apr 2, Trenton and Seabrook Farms around Apr 10, and Sussex in the Skylands around May 1. Each station carries its own dates: Atlantic City Mar 26 and Sussex May 1 at the median.