Soil Temperature for Outdoor Marigold Seeds

Gauging Soil Temperature

• Short of using a thermometer to check the soil's temperature, you'll know that soil is usually ready in northern areas such as Michigan or Montana to receive marigold seeds when the air temperature remains above 60 degrees overnight, as daytime temperatures climb above that during the day in mid- to late spring.

Temperature Control

• The warmer the soil, the more quickly the marigold seeds germinate, which is why many gardeners choose to start their own seeds indoors where the temperature of the soil is easier to control and monitor. If you take this approach, start the marigolds in a dark spot with an air temperature of 75 to 80 F about six weeks before the last frost.

Outdoor Considerations

• Marigolds are heat-tolerant annuals that do best in areas that receive at least 6 to 8 hours of direct sunlight per day, making them ideal for gardens with a southern exposure. They are also drought tolerant and need watering only when the soil appears dry to the touch.

Insulation

• Though it may take a bit longer, marigold seeds can germinate in soil that isn't quite warm enough, a process that you can help along by putting down about 2 inches of mulch in the fall. You can add more mulch once the marigolds have germinated and grown several inches to keep the soil warm and eliminate weeds.