A few weeks ago in late February we had a snow storm. Three feet of snow fell within a few days. Right before the storm we had a false spring. A few warm sunny days, a reprieve from the long winter. I started to weed our garden and marveled at all the bright blooming calendula flowers. After the snow fell I thought about those cute little flowers, the first to bloom this year. Low and behold even after the snow all of their cheerful faces are still shining out in the garden. A perfect plant, incredibly resilient and incredibly useful. Calendula will always have a place in my garden. 

Overview

Calendula is a member of the Asteraceae family. One of the biggest flowering plant families. Asteraceae is home to so many familiar plants, including lettuce, chamomile, radicchio, and dandelion to name a few. There are at least 25 different known species of calendula. Originating in the Mediterranean region it is now found naturalized throughout Europe and North America.

Calendula has a number of common names including pot marigold, gold bloom and my favorite, poet’s marigold. There is no relation between calendula and our other garden favorite marigolds. Marigolds are also in the Aster family but are a different species and native to Africa.

The flowers range from yellow to orange with greater color variation in ornamental cultivars. There are two general flower morphologies. One with ligulate or strap shaped petals that are fused together. The other has tubular shaped petals. They have pale green leaves which are sticky and oval shaped without serration. Both the flowers and the leaves are edible. Plants will grow into a small bush shape. 

Calendula is a well known plant throughout the world. There is a lot of research exploring the genetic, medicinal and biological habits of calendula. Due to their cultural significance a lot of work has gone into breeding different varieties. The breeding work attempts to create unique ornamental varieties and plants with larger flowers or higher oil contents. Breeding for disease and pest resistance is also a main consideration.

The most widely cultivated species is Calendula officinalis. It is an herbaceous short lived perennial. If you live in a place with very cold winters it can be grown as an annual. 

Uses

Traditional and herbal medicine systems all over the world make use of calendula.  It is used in oils, ointments, teas, tinctures and fresh as a succus. It is purported to have a great many uses ranging from anti-bacterial, anti-viral and anti-inflammatory properties to homeopathic uses for impaired vision and ulcers. 

It seems like just about every healing salve has calendula infused oil in it. It does wonders for healing scars and small burns and cuts. When I worked at a large herb farm we would spend entire weeks picking calendula flowers. After a full day picking instead of having blisters and calluses our hands would be soft albeit a little sticky. 

Calendula is high in carotenoids which are important in Vitamin A production and other compounds beneficial to human health like flavonoids and antioxidants.  I really like to add dry calendula petals to loose leaf tea blends. They make for a happy looking cup of tea. Petals are also used as a cheap alternative to saffron. Furthermore, many cosmetic products make use of calendula.

A fairly inocuous plant, this lovely herb can be used regularly. If you are allergic to ragweed or other asters this might not be the right choice for you. It is also recommneded that pregnant and breastfeeding women do not use calendula. There is a lot of great information regarding calendula uses for you to explore if you are looking to dive into herbal medicine.

Another fun way to use calendula is for natural dyeing. Dye made from the flowers can produce  colors that range in tones of yellow to pale greenish brown. Like most natural dyes the color produced will depend on the fiber and the mordant that you use. 

How to Grow

Calendula is cold hardy and can germinate at a wide range of temperatures. It can be directly sown in the garden when soil temperatures are about 55 degrees or seeded into flats indoors and transplanted into prepared beds after 6 weeks.  It generally does pretty well if you direct seed into your garden. Plants have a tap root which can sometimes make transplanting a little tricky. Calendula self seeds very easily and the following year you will see tons of seedlings where your plants were. 

Space your plants 12 inches apart in rows for ease of harvest. If you are looking for a wildflower look in your garden, intersperse the calendula in the middle area of your beds. Plants will grow to about 30 inches but this will vary depending on soil conditions and watering.

When the plants are about 9 inches tall pinch them back to promote lateral branching. Pinch or snip the top of the plant back to a growth node.  Calendula is fairly upright and does not require a trellis. 

If you live in a place with mild winters your plants will survive and be short lived perennials. You can also sow seeds in the fall.

Due to the significance of calendula as a crop around the world there have been a number of agricultural studies to determine the impact of fertilizer and water on calendula yields. Plants grown in organic compost were found to produce the best.

Calendula can withstand drought conditions as well making it a great plant for low water gardens. Although less watering has an impact on the weight of the plant material it was found that stressed plants yielded higher quality oil. Early maturing varieties like ‘Alpha” produce higher weights of plant material. ‘Resina’ produces the most oil hence the name. Something to consider if your main goal is to make medicine from your plants. 

How to Harvest 

Depending on what your intentions are you will want to harvest the plant differently. If you are harvesting for cut flowers you need to cut the stem low, close to the stalk of the plant. This will give you a long enough stem for your bouquet. There are some varieties like ‘Princess Mix’ calendula which are bred specifically for cut flower use.

All of the aerial, or above ground portions of calendula can be used. The flowers are the most commonly used part of the plant for herbal medicine and natural dyes. The flowers will pop off the plant easily into your hand. You can use garden snips or you can slide the flower through your fingers and pull.  Collect flowers in a basket or bucket. 

Yields increase from the first harvest to the 5th harvest and then begin to taper off in the last few harvests. You should be able to repeatedly harvest your plant starting in late spring until fall. 

To dry, lay flowers in a single layer onto screens or sheets. Provide airflow and dry the flowers in a dark dry place.  I have a nice herb drying rack that has a hanging point and round mesh drying racks. I hang it in my closet which works pretty well. 

 Happy Planting!

Taryn Hunter

References

Abdelwahab, S. I., Taha, M. M. E., Taha, S. M. E., & Alsayegh, A. A. (2022). Fifty-year of global research in Calendula officinalis L.(1971− 2021): A bibliometric study. Clinical Complementary Medicine and Pharmacology, 2(4), 100059.

Anderson, V. M., Archbold, D. D., Geneve, R. L., Ingram, D. L., & Jacobsen, K. L. (2016). Fertility source and drought stress effects on plant growth and essential oil production of Calendula officinalis. HortScience, 51(4), 342-348.

AshwlayanVD, K. A., & Verma, M. (2018). Therapeutic potential of Calendula officinalis. Pharm Pharmacol Int J, 6(2), 149-155.

Baciu, A. D., Pamfil, D., Mihalte, L., Sestras, A. F., & Sestras, R. E. (2013). Phenotypic variation and genetic diversity of Calendula officinalis (L.). Bulgarian Journal of Agricultural Science, 19(1), 143-151.

Betül, A. V. C. I., & Memet, İ. N. A. N. (2021). Comparing of cultivated annual and perennial Calendula officinalis L. species. Kahramanmaraş Sütçü İmam Üniversitesi Tarım ve Doğa Dergisi, 24(3), 579-585.

Khalid, K. A., & da Silva, J. T. (2012). Biology of Calendula officinalis Linn.: focus on pharmacology, biological activities and agronomic practices. Medicinal and Aromatic Plant Science and Biotechnology, 6(1), 12-27.

Paim, L. F. N. A., Fontana, M., Winckler, M., Grando, A. A., Muneron, T. L., & Roman Júnior, W. A. (2010). Assessment of plant development, morphology and flavonoid content in different cultivation treatments of Calendula officinalis L:, Asteraceae. Revista Brasileira de Farmacognosia, 20, 974-980.

Preethi, K. C., Kuttan, G., & Kuttan, R. (2006). Antioxidant Potential of an Extract of Calendula officinalis. Flowers in Vitro. and in Vivo. Pharmaceutical biology, 44(9), 691-697.

Petruzzello, M. (n.d.). Asteraceae. Encyclopædia Britannica. https://www.britannica.com/plant/Asteraceae

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