City	Sow outdoors	Last frost
Kansas City	Mar 21 to Apr 18	Apr 4
St. Louis	Mar 18 to Apr 15	Apr 1
Springfield	Mar 21 to Apr 18	Apr 4
Columbia	Mar 22 to Apr 19	Apr 5
Independence	Mar 27 to Apr 24	Apr 10
Lee's Summit	Mar 24 to Apr 21	Apr 7
O'Fallon	Mar 27 to Apr 24	Apr 10
St. Charles	Mar 25 to Apr 22	Apr 8
St. Joseph	Apr 5 to May 3	Apr 19
Blue Springs	Mar 24 to Apr 21	Apr 7
St. Peters	Mar 26 to Apr 23	Apr 9
Joplin	Mar 26 to Apr 23	Apr 9
Florissant	Mar 19 to Apr 16	Apr 2
Wentzville	Mar 27 to Apr 24	Apr 10
Chesterfield	Mar 21 to Apr 18	Apr 4
Jefferson City	Mar 25 to Apr 22	Apr 8
Cape Girardeau	Mar 22 to Apr 19	Apr 5
Oakville	Mar 23 to Apr 20	Apr 6
Wildwood	Mar 29 to Apr 26	Apr 12
University City	Mar 18 to Apr 15	Apr 1
Liberty	Apr 5 to May 3	Apr 19
Ballwin	Mar 21 to Apr 18	Apr 4
Kirkwood	Mar 18 to Apr 15	Apr 1
Raytown	Mar 24 to Apr 21	Apr 7
Mehlville	Mar 23 to Apr 20	Apr 6
Maryland Heights	Mar 21 to Apr 18	Apr 4
Gladstone	Mar 21 to Apr 18	Apr 4
Grandview	Mar 24 to Apr 21	Apr 7
Raymore	Mar 30 to Apr 27	Apr 13
Nixa	Apr 1 to Apr 29	Apr 15
Belton	Mar 30 to Apr 27	Apr 13
Hazelwood	Mar 19 to Apr 16	Apr 2
Ozark	Apr 1 to Apr 29	Apr 15
Webster Groves	Mar 18 to Apr 15	Apr 1
Sedalia	Apr 4 to May 2	Apr 18
Republic	Mar 26 to Apr 23	Apr 9
Old Jamestown	Mar 19 to Apr 16	Apr 2
Arnold	Mar 26 to Apr 23	Apr 9
Rolla	Mar 22 to Apr 19	Apr 5
Warrensburg	Mar 31 to Apr 28	Apr 14
Affton	Mar 18 to Apr 15	Apr 1

Questions

When should I plant swiss chard in Missouri?

In Kansas City, sow outdoors from March 21 to April 18. Across Missouri the window opens between March 18 and April 5, depending on the local last frost.

How is this date worked out?

Sow outdoors from 2 weeks before to 2 weeks after the last frost. Frost dates are NOAA 1991–2020 averages for the weather station nearest each city.