Calendula officinalis, commonly known as pot marigold, is a vibrant annual herb. This plant is distinct from the common French or African marigolds (Tagetes species) and has a long history of use in both culinary and herbal traditions. The flowers are frequently dried for use in teas, or infused into oils to create therapeutic salves and lotions. Proper harvesting and drying techniques are necessary to preserve the flower’s maximum potency and brilliant color for long-term storage.
Optimal Timing and Selection
The best time to harvest calendula flowers is when the blooms are fully open and exhibiting their most intense color. Selecting flowers at their peak ensures the highest concentration of beneficial compounds, such as resins and volatile oils. It is important to avoid any flowers that are beginning to fade, wilt, or show signs of developing a seed head, as their potency will have already begun to diminish.
The ideal time of day for collection is mid-morning, shortly after the morning dew has completely evaporated from the petals. Harvesting at this time ensures the flowers have the lowest possible surface moisture, which minimizes the risk of mold during the drying process. Picking the flowers before the heat of the afternoon helps maximize the retention of aromatic and medicinal constituents. Harvesting the blooms frequently, roughly every two to three days, acts as a form of deadheading, encouraging the plant to produce a continuous flush of new flowers throughout the growing season.
The Physical Harvesting Technique
The entire flower head, or capitulum, is the desired part for drying and preservation due to its high concentration of beneficial compounds. When removing the bloom, focus on harvesting the flower just below the green base, known as the calyx. The calyx and the sticky, resinous bracts contain a significant amount of therapeutic resin.
To detach the head, use clean, sharp scissors or small snips to make a clean cut directly beneath the calyx. Alternatively, the head can be cleanly pinched off using the thumbnail and forefinger. The sticky residue left on the fingers is a good indicator that the resinous compounds have been successfully collected with the bloom. After harvesting, trim any remaining long, bare stems on the plant back to the first set of leaves, which helps to promote the growth of new flowering side shoots.
Drying and Long-Term Storage
Immediately following the harvest, the flowers should be brought indoors and prepared for drying without being washed. Washing introduces excess moisture and increases the risk of mold formation. Instead, gently shake the flower heads to dislodge any dirt or small insects before laying them out to dry. The whole flower heads can be dried intact, as the calyx contains important medicinal properties.
The flowers must be dried in a single layer on screens or trays that allow for maximum air circulation. A warm, dark, and well-ventilated location is best, as direct sunlight can cause the petals to bleach and degrade the therapeutic compounds. If using a food dehydrator, set the temperature to a very low setting, ideally below 95°F, to prevent heat damage to the volatile oils. Full drying can take anywhere from a few days in a dehydrator to two or three weeks when air-drying, depending on the humidity.
The calendula is fully dry and ready for storage when the flowers feel brittle and the center of the flower head crumbles easily when gently pressed. Once completely dry, the material should be transferred to an airtight container, such as a glass mason jar, and stored in a cool, dark location. Storage protects the dried flowers from light and oxygen, which cause the color and potency to diminish.