Seed Starting Calendar for South Carolina

Count back from the median last frost where you garden. At Columbia (Columbia Owens Downtown Airport) that date is March 13, so for spring 2027 onions start indoors Dec 5 to Dec 19, peppers Jan 16 to Jan 30 and tomatoes Jan 23 to Feb 6. Across South Carolina's 101 NOAA stations the median last frost runs from Mar 3 to Apr 10 for the middle 90 percent, so a garden near Jocassee 8 WNW starts later than one near Charleston City.

It depends on the station. The earliest median last spring freeze in South Carolina is February 4 at Charleston City; the latest is April 26 at Jocassee 8 WNW. A median is a coin flip: at Columbia the last 32°F freeze comes after March 13 in half of years, and has passed by March 31 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 Columbia is Mar 20 to Mar 27 in 2027. Tomatoes are frost tender, so the date to watch is March 31, when 9 of 10 springs at Columbia have had their last 32°F night. Hardening off starts two weeks before setting out (Mar 6 to Mar 20).

Clemson Cooperative Extension, Home & Garden Information Center (HGIC) publishes planting months by region (Coastal Plain, Piedmont). For Coastal Plain, tomatoes go in during March, April and July. Seeds for transplants go in 4 to 10 weeks ahead of those months, depending on the crop.

Clemson Cooperative Extension, Home & Garden Information Center (HGIC)'s Planning a Garden puts it this way: "To determine when to plant cool- and warm-season vegetables in South Carolina, refer to Table 1. Knowing the number of days required to reach maturity, a gardener could determine the appropriate planting time for seeds and transplants by using the average dates of the first and last freezes in their 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 Columbia that is Jan 16 to Jan 30 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.

Charleston reaches its median last frost around Feb 4, Columbia around Mar 13, Greenville in the Upstate around Mar 16, and Rock Hill near the North Carolina line around Mar 31. Each station carries its own dates: Charleston Feb 4 and Rock Hill York County Airport Mar 31 at the median.