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

Questions

When should I plant sunflowers in Missouri?

In Kansas City, sow outdoors from April 4 to April 25. Across Missouri the window opens between April 1 and April 19, depending on the local last frost.

How is this date worked out?

Sow outdoors up to 3 weeks after the last frost. Frost dates are NOAA 1991–2020 averages for the weather station nearest each city.