Calendula

Calendula officinalis

Calendula is also known as pot marigold, but is not related to the common garden marigold, Tagetes spp..  Historically, calendula blossoms have been used to color broth, rice, and other foods as a substitute for saffron, but now is primarily used topically as skin cream, oil, or lotion.

Family:  Asteraceae
Life cycle:  Herbaceous annual. (Zone 3-9)
Native:  Europe to Africa
Height:  12-15 inches
Sun:  Full sun. Tolerates hot conditions.
Soil:  Well drained to poor, not overly moist. Prefers loam.
Water:  Moderate
Flowers:  Flowers are bright yellow and orange, single or double , and bloom from early summer until a killing frost.  Flowers close up at night and reopen in the morning.  Calendula will bloom from summer to early fall if deadheaded in a timely manner.  Flowers attract beneficial insects.
Propagation:  Sow seed directly in the field, they need no treatment.  Seed can also be started indoors and transplanted out.  Seed will germinate in about 1-2 weeks and will have around 80% germination.  Space 10-12 inches apart. Reseeds itself readily.
Pests:  Calendula will attract whitefly, aphids, and thrips.  Another source also reported cucumber beetles and blister beetles.  Damping off can be a problem in the greenhouse.
Harvesting:  Harvest flowers by hand when they are fully open. Avoid flowers that have gone to seed because medicinal properties are not as active.  If plants are allowed to go to seed they will quit growing. If harvesting for essential oil, (process) 3 weeks after harvesting for flowers.  One source reported that flowers need to be picked at least 3 times per week for optimal quality.  It is estimated that one acre of calendula could keep a crew of 3 to 4 people busy every day for 3 or 4 months, with dry flower yields of 400 to 600 lb per acre.  Flower petals dry quickly, but the rest of the head requires at least a week in the drying oven.
Parts used:  Flowers primarily, fresh or dried.
Used as:  Medicinal food, food coloring,  infusion, tincture, compress, poultice, ointment, salve, cream, balm, foot soak, bath herb, infused oil, liniment, cosmetics, insect repellent. Petals have a nutty flavor.
Medicinal Benefits:  Several clinical studies have been conducted on calendula, and show antimicrobial activity against several organisms, antiviral activity, and wound healing promotion in skin tissue.  Calendula was also shown to induce the formation of new blood vessels, also important in wound healing.  Approved in Europe for inflammation of the mouth and pharynx, and wounds and burns.  Typical forms are as gel, ointment, tincture, tea, shampoo, and hand cream.
Market Potential:  Moderate to high, preferred in dry form.  Prices range from $4.80 to $39.00 per lb dw for flowers.

KSU Field Trial Data - 2000-2002.

Summary of Field Trial Data:  Though the plants were in full flower most of the years when we harvested in the fall, to get the full yield data, one must conduct repeated harvests, at least weekly, if not more often.  This was beyond the capabilities of this project.  A rough estimate might be 25% of the top dry weight as flowers over the growing season.  For optimal quality, and repeated harvests, this crop must be harvested by hand, but mechanization might be possible for a one-time harvest.  This would imply some specialization in this crop, and/or other flowering crops, in order to pay for the infrastructure/equipment needed.  A definite contract and/or market should be secured before taking on this debt.  In our field plots, the calendula was surprisingly robust, even in our hot, dry, windy summers.  However, some irrigation is needed for optimal yields.  This makes a nice plant for the flower garden.