The central rule of thumb is to plant after the last day of expected frost in your area. Remember, marigolds are annuals and are frost sensitive. A few days too early can mean the difference between a beautiful flower garden….and a disaster.
When you order plants online or through a catalog it is very useful for you to know what will have the best success in your zone.
Most plants are marked with a zone number. Use this map to know what plants will do best in your zone.

USDA PLANTING ZONE MAP

Indicator Plant Examples Listed by Zone
Plant Hardiness Zones, Details

NOTE: The dates below are for the Northern Hemisphere
(Adjust appropriately for Southern Hemisphere) Zone 1
Average dates Last Frost = 1 Jun / 30 Jun
Average dates First Frost = 1 Jul / 31 Jul Note: Vulnerable to frost 365 days per year
Average dates Last Frost = 1 May / 31 May
Average dates First Frost = 1 Aug / 31 Aug
Zone 3
Average dates Last Frost = 1 May / 31 May
Average dates First Frost = 1 Sep / 30 Sep
Zone 4
Average dates Last Frost = 1 May / 30 May
Average dates First Frost = 1 Sep / 30 Sep
Zone 5
Average dates Last Frost = 30 Mar / 30 Apr
Average dates First Frost = 30 Sep / 30 Oct
Zone 6
Average dates Last Frost = 30 Mar / 30 Apr
Average dates First Frost = 30 Sep / 30 Oct
Zone 7
Average dates Last Frost = 30 Mar / 30 Apr
Average dates First Frost = 30 Sep / 30Oct
Zone 8
Average dates Last Frost = 28 Feb / 30 Mar
Average dates First Frost = 30 Oct / 30 Nov
Average dates Last Frost = 30 Jan / 28 Feb
Average dates First Frost = 30 Nov / 30 Dec
Zone 10
Average dates Last Frost = 30 Jan or before
Average dates First Frost = 30 Nov / 30 Dec
Zone 11
Free of Frost throughout the year.