As the bright yellow and orange calendula blooms start drying up and fading out, watch for the seeds to mature at the base of the petals. At first the seeds will be green. For best results you want to leave them on the plant until the seeds turn brown. Then pick the dried up flower from the plant.
The seeds will almost fall off into your hand. If not, rotate them between your fingers to encourage the seeds to pull away from the base. Collect these and save for next year. Or sometimes I just sprinkle them back into the garden. They may not do as well this way as if you grow them inside in the spring, but many of them will grow.
Propagating new herb plants can be fun.
Some other great herbs to collect seeds from are basil, fennel, parsley, mullien, chamomile and dill.
Have you collected any of these? Or any others?