Seed Starting Calendar for Missouri

Count back from the median last frost where you garden. At Kansas City (Kansas City Downtown Airport) that date is April 4, so for spring 2027 onions start indoors Dec 27 to Jan 10, peppers Feb 7 to Feb 21 and tomatoes Feb 14 to Feb 28. Across Missouri's 167 NOAA stations the median last frost runs from Mar 31 to Apr 23 for the middle 90 percent, so a garden near Rosebud starts later than one near Caruthersville.

It depends on the station. The earliest median last spring freeze in Missouri is March 24 at Caruthersville; the latest is April 27 at Rosebud. A median is a coin flip: at Kansas City the last 32°F freeze comes after April 4 in half of years, and has passed by April 20 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 Kansas City is Apr 11 to Apr 18 in 2027. Tomatoes are frost tender, so the date to watch is April 20, when 9 of 10 springs at Kansas City have had their last 32°F night. Hardening off starts two weeks before setting out (Mar 28 to Apr 11).

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

University of Missouri Extension's Master Gardener: Vegetables (MG5), Seeds and transplants puts it this way: "The proper time for sowing seeds depends primarily on when plants may normally be moved outdoors. This period ranges from four to 10 weeks, depending on the growing conditions and the seedlings’ expected growth rate (Table 2)." 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 Kansas City that is Feb 7 to Feb 21 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.

St. Louis and Kansas City reach a median last frost around Apr 1 to Apr 4, Joplin around Apr 9, West Plains in the Ozarks around Apr 16, and Kirksville in the north around Apr 19. Each station carries its own dates: St. Louis Apr 1 and Kirksville Regional Airport Apr 19 at the median.