E. Calendula is an annual at temperate climates.
Calendula, often referred to as Pot Marigold, is a member of the Asteraceae family and is native to southern Europe. There are over a hundred varieties of calendula, and the flowers can range from small yellow blossoms to big sunbursts of flowers up to three inches wide and bright orange in color. The aerial part of the plant is upright and bushy, growing two to three feet tall with bright green leaves. The flowers are sticky and fragrant, containing medicinal resins. For commercial growing we use the Erfurter Orangefarbige variety, as they produce larger, dense flowers with high resin content.
Calendula does well in full sun and in well drained soil that is rich in organic matter. It does not require specialized nutrients but likes good fertility and soil organic matter. This strikingly beautiful plant is one that is great to showcase! People and pollinators will flock to its lovely color and sunny disposition. Plant calendula where you can see it and also where there is easy access to drying facilities, as harvesting will be done every few days from early summer to early fall.
Calendula seeds should be sown approx. one quarter to one half inch or covered lightly with potting medium. On our farm we grow plugs in the greenhouse and transplant them into well prepared beds. This gives us a jump on the season and helps calendula get established and outcompete weeds. Calendula can also be direct seeded into the field, but extra care should be taken to prepare the bed and prevent weeds. You can grow your plugs for four to size weeks, then harden them off thoroughly before transplanting.
Calendula plant spacing is one foot in a single row, and at lest thirty six inches between rows. Be careful not to grow your calendula plants too closely together, as a single, fully mature plant can grow up to three feet wide and three feet tall. As a member of the Asteraceae family, calendula is susceptible to Aster Yellows, a viral disease carried by leafhoppers that causes deformities to the flowers. A good practice would be to avoid planting members of the Asteraceae family in the same growing area year to year – instead, rotate your plants into different areas. Another thing to consider is that calendula readily self seeds and will quickly hybridize its genetics when planted near other calendula varieties. Therefore, it can be very difficult to produce a second true seed crop as pollen from nearby ornamental varieties will readily be brought by insects. For this reason, it’s better to start with a brand new seed crop each year – as opposed to saving your seeds from previous harvests. This is the only way to ensure the same variety year to year.
Calendula blossoms are used both internally and externally and have strong fresh and dried applications. Externally, the flowers are used to heal burns, cuts, and skin abrasions. Not only does calendula promote cellular healing, it is also antiseptic and antimicrobial and helps fight infection. That is why it is a favorite for both first-aid kits and cosmetic purposes and is used in all sorts of topical applications such as liniments, slaves, oils, creams, and serums. Calendula can also be used antibiotically to clean wounds and is often paired with such herbs as spilanthese, myrrh, and peppermint to use as a mouthwash. Internally, calendula is a strong lymphatic, excellent for tonifying the lymphatic system and flushing toxins. Calendula is a cooling herb that has anti-inflammatory and bitter properties and can be take internally in tea or tincture form.
Calendula is harvested when blossoms are fully open but before they begin to go to seed. Harvesting is best done by hand. The easiest method is to use your thumb and index finger to form a pinch with your fingernails – snip stem of the flower head as close to the base of the flower as possible. It’s best to only harvest those calendula flowers which are already open and not in bud stage. Keeping up with the harvest is important, not only to get the blossoms at their peak but also to maintain the blooming cycle (the more you pinch blooms, the more blooms will be developed.) Should many of the flowers on a single plant move to seed, you will likely notice a quick turn in the plants life cycle as growing is now complete. Calendula flowers should be harvested during the hottest part of the day. This ensures the maximum amount of resin moving into the flower heads. Your fingers should be nice and sticky when you daily harvest is complete.
Post Harvest Drying Conditions
Drying calendula can be tricky. Any remaining moisture in a flower head can cause rampant mold growth in an otherwise container of perfectly dried flowers. The key to drying is careful monitoring. Different parts of the flower head dry at different times. Petals of calendula dry the most quickly, while the dense flower head can take much longer to dry. For optimum color retention, dry your calendula in complete darkness and at temperatures of 95 to 100 degrees F. Good airflow is also essential; make sure your fans are blowing directly over the racks. Placing calendula in a single layer on its tray greatly helps with evenly drying. Depending on conditions, calendula can take up to a week or more to completely dry. How do you know when they’re done? Its important to examine multiple flowers for dryness. They should be crisp and come off easily. Split a flower open – the center should be dry but somewhat pliable. The centers contain the most resin and won’t actually “snap,” very well because of this. Finally, run your hands within a batch of dried calendula flowers and listen for the sound of rustling dried leaves. If you don’t hear this papery, autumnal sound, allow your flowers to dry longer. After you calendula is stored, it’s good practice to check your container a few times in the upcoming weeks for any rogue mold growth.
Pests and Diseases
The only pest we’ve encountered with calendula is Aster Yellows, a disease carried by leafhoppers. There is no treatment for aster yellows. The best course of action is to remove the whole diseased plant and use proper crop rotations to limit the spread of leaf hoppers.