Calendula (// Ca-lén-du-la), marigold, is a genus of about 12–20 species of annual or perennial herbaceous plants in the daisy family Asteraceae, native to an area from Macaronesia east through the Mediterranean to Iran. Calendula should not be confused with other plants that are also known as marigolds, such as corn marigold, desert marigold, marsh marigold, or plants of the genus Tagetes.
The name "calendula" is a modern Latin diminutive of calendae, meaning "little calendar", "little clock" or possibly "little weather-glass". The common name "marigold" possibly refers to the Virgin Mary. Claims that its old Saxon or Anglo-Saxon name is 'ymbglidegold' are unsubstantiated, as is the claim that this means 'it turns with the sun'.
The most commonly cultivated and used member of the genus is the pot marigold (Calendula officinalis). Herbal and cosmetic products named 'calendula' invariably derive from C. officinalis.
Plant pharmacological studies have suggested that Calendula extracts have anti-viral, anti-genotoxic, and anti-inflammatory properties in vitro. In herbalism, Calendula in suspension or in tincture is used topically for acne, reducing inflammation, controlling bleeding, and soothing irritated tissue. There is limited evidence that Calendula cream or ointment is effective in treating radiation dermatitis. In a randomized study of 254 radiation patients, topical application of 4% calendula ointment resulted in far fewer occurrences of Grade 2 or higher dermatitis than occurred in the group using trolamine. Calendula users also experienced less radiation-induced pain and fewer breaks in treatment.
Calendula has been used traditionally for abdominal cramps and constipation. In experiments with rabbit jejunum the aqueous-ethanol extract of Calendula officinalis flowers was shown to have both spasmolytic and spasmogenic effects, thus providing a scientific rationale for this traditional use. An aqueous extract of Calendula officinalis obtained by a novel extraction method has demonstrated anti-tumor (cytotoxic) activity and immunomodulatory properties (lymphocyte activation) in vitro, as well as anti-tumor activity in mice.
Calendula has been used traditionally as both a culinary and medicinal herb. The petals are edible and can be used fresh in salads or dried and used to color cheese or as a replacement for saffron. Medicinal use of Calendula dates back to the Ancient Greeks. An anti-fungal and disinfectant, calendula is thought to have been used as a treatment for wounds and minor fungal infections. It has also been described as a traditional remedy for menstrual cramps and irregular periods.
The yellow-orange and pale-yellow petals of the calendula plant are said to have been used for dye before synthetic dyes were available. Another preparation is calendula oil, which was used as a healing ointment for cuts, burns, bruises, warts, aches and pains. 
- Calendula arvensis (Vaill.) L. – Field Marigold
- Calendula denticulata Schousb. ex Willd.
- Calendula eckerleinii Ohle
- Calendula incana Willd.
- Calendula incana subsp. algarbiensis (Boiss.) Ohle
- Calendula incana subsp. maderensis (DC.) Ohle – Madeiran Marigold
- Calendula incana subsp. maritima (Guss.) Ohle – Sea Marigold
- Calendula incana subsp. microphylla (Lange) Ohle
- Calendula lanzae Maire
- Calendula maritima Guss.
- Calendula maroccana (Ball) Ball
- Calendula maroccana subsp. maroccana
- Calendula maroccana subsp. murbeckii (Lanza) Ohle
- Calendula meuselii Ohle
- Calendula officinalis L. – Pot Marigold
- Calendula palaestina Boiss.
- Calendula stellata Cav.
- Calendula suffruticosa Vahl
- Calendula suffruticosa subsp. balansae (Boiss. & Reut.) Ohle
- Calendula suffruticosa subsp. boissieri Lanza
- Calendula suffruticosa subsp. fulgida (Raf.) Guadagno
- Calendula suffruticosa subsp. lusitanica (Boiss.) Ohle
- Calendula suffruticosa subsp. maritima (Guss.) Meikle
- Calendula suffruticosa subsp. monardii (Boiss. & Reut.) Ohle
- Calendula suffruticosa subsp. tlemcensis Ohle
- Calendula tripterocarpa Rupr.
The endangered Calendula maritima
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- Ukiya M, Akihisa T, Yasukawa K et al. Anti-inflammatory, anti-tumor-promoting, and cytotoxic activities of constituents of pot marigold (Calendula officinalis) flowers. (2006). J Nat Prod. 69:1692-1696.
- Yoshikawa M, Murakami T, Kishi A et al. (2001). Medicinal flowers.III. Marigold.(1): hypoglycemic, gastric emptying inhibitory, and gastroprotective principles and new oleanane-type triterpene oligolycosides, calendasaponins A, B, C, and D, from Egyptian Calendula officinalis. Chem Pharm Bull. 49:863-70.
- Jimenez-Medina E, Garcia-Lora A, Paco L et al. (2006). A new extract of the plant Calendula officinalis produces a dual in vitro effect: cytotoxic anti-tumor activity and lymphocyte activation. BMC Cancer. 6:6.
- Duran, V; Matic, M; Jovanovć, M; Mimica, N; Gajinov, Z; Poljacki, M; Boza, P (2005). "Results of the clinical examination of an ointment with marigold (Calendula officinalis) extract in the treatment of venous leg ulcers". Int J Tissue React. 27 (3): 101–6. PMID 16372475.
- Pommier, P; Gomez, F; Sunyach, MP; D'hombres, A; Carrie, C; Montbarbon, X (2004-04-15). "Phase III randomized trial of Calendula officinalis compared with trolamine for the prevention of acute dermatitis during irradiation for breast cancer". J Clin Oncol.;():1447-53 22 (8): 1447–53. doi:10.1200/JCO.2004.07.063. PMID 15084618.
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- Pommier P. et al. J Clinical Oncol. 2004; 22:1447-1453
- Bashir S, Janbaz KH, Jabeen Q et al. (2006). Studies on spasmogenic and spasmolytic activities of Calendula officinalis flowers. Phytother Res. 20:906-910.
- "About Herbs, Botanicals & Other Products: Calendula". Memorial Sloan-Kettering Cancer Center.
- Reider, N; Komericki, P; Hausen, BM; Fritsch, P; Aberer, W (2001). "The seamy side of natural medicines: Contact sensitization to arnica (Arnica montana L.) and marigold (Calendula officinalis L.)". Contact dermatitis 45 (5): 269–72. PMID 11722485.
-  Spotlight on Marigold
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