Here in Alabama, November is the time to collect dried French Marigold seeds for planting next spring. Stop pinching the flower heads in mid-September to allow plenty of time for them to dry out. Then on a dry sunny day in November pinch the dried flowers off and place them on something flat where they can be crushed and spread out for further drying. After a week or so place the dried, crushed flower heads in zip-loc bag then store in a cool dry place until ready to plant (we keep them in the frig).
Some folks prefer to separate the seed from the dried flower petals but we crush and save the entire flower. When we’re ready to plant we simply spread about 2″ of soil in a flat, crumble the crushed mess over it, and then spread another 1/4″ of soil over that. Next we water the container really good and set it in a warm sunny place. French Marigolds can be transferred to the garden after their true leaves are 10-14 days old (as long as night-time temperature are at least 60 degrees farenheit and the soil has warmed sufficiently). Or, they can be transplanted into larger containers and set in the garden when about 6-8 weeks old.
Bumble bees love them! We had bumble bees in the garden until the temperature dipped below freezing just about two weeks ago. It’s not a good idea to plant them with beans or peas because pollinators seem to prefer them thus possibly making the fruit set lower than if the marigolds weren’t there at all.