Harvesting and Saving Marigold Seeds from SFGate
Saving marigold seeds for next season is a fairly simple process, requiring only a paper towel to dry the seeds, a paper envelope for storage, and a dark, cool place to store the seeds until you’re ready to plant them. Harvest your seeds when the marigolds begin to dry out, the petals are browning, the base (or seed pod) is beginning to slightly brown, and some green is still on the base.
Remove dried marigold flower heads from the stem by holding the base, pulling off and discarding dried petals and leaves. You’ll see long, pointy seeds attached to the base that are dark on one end and light on the other. Remove them and discard the base.
Separate and spread the seeds on a paper towel. Allow them to air-dry, uncovered, for about a week. Place in a paper bag (plastic will retain moisture, which may lead to rot or mold). Store the envelope in a cool, dry, dark place until the following season.