Put the blossoms still attached to their stems and leaves into a large bowl filled with clean cold water. Swish, let the dirt settle, lift up the calendula, and empty the water. Repeat this step at least one more time or until the water runs clean.
Place the calendula on a towel to dry. Cover with a second towel and gently blot.
Hang from a line in small bundles, not tightly packed large bundles, to encourage air flow. It will take several days for the blossoms to completely dry. The base on the underside will take the longest.
Once fully dry, cut the blossoms from the stems and garble the leaves (you will not be using the stems; they can be added to your compost pile). Loosely pack the flowers and leaves in jars with tight fitting lids and store out of direct sunlight while the herb conditions.
Shake the jars daily to separate the pieces and also to check for moisture and mold. If condensation develops in a jar, remove all of the calendula and recommence air drying in a well ventilated location such as on a screen or drying rack.
After you have conditioned in this way for 7 to 10 days, you can pack the jars more tightly; store them in a cool, dry, dark location.