Genus & Name

Calendula is a genus of 15–20 herbaceous plants in the daisy family (genus Asteraceae) that are commonly known as marigolds. They are native to southwest Asia, western Europe, Macaronesia, and the Mediterranean. 

The Latin name for the genus Calendula means "little calendar", "little clock". The most commonly cultivated member of the genus is Calendula officinalis, the pot marigold. Popular herbal and cosmetic products called "Calendula" are always derived from Calendula officinalis.

History
Calendula was used in historical times for headaches, red eyes, fever, and toothaches.

The ancient Romans and Greeks used the golden Calendula in many traditions, sometimes wearing crowns or garlands made from this flower.

However, the most common use in historical times was in cooking, and the plant was used for both its color and flavor. They were used in pasta, wine, porridge, and puddings. In English cuisine, marigolds were often cooked in the same pot with spinach and used to flavor the food. According to the 16th-century Englishman John Gerard, every proper Dutch soup of his time would include marigold petals.

Uses

Cuisine:
Also known as "poor man's saffron", the petals are edible and can be used fresh in salads or dried and used to color cheese or as a substitute for saffron. Marigolds have a mildly sweet flavor that is slightly bitter and as it dries these flavors become more intense. It can be used to add color to soups, stews, meat dishes, creams and liqueurs.

Dyes:
The dye can be extracted from the flower and produces shades of honey, golden orange, light brown and vibrant yellow.

Chemistry:
Her flowers Calendula officinalis contains flavonol glycosides, triterpene oligoglycosides, oleanane-type triterpene glycosides, saponins, and a sesquiterpene glycoside.

Pharmacological effects:
Calendula officinalis oil is still used medicinally as an anti-inflammatory and a remedy for healing wounds & skin conditions. Calendula ointments are skin products available for use on minor cuts, burns, eczema and skin irritations. It has antiseptic & astringent properties.

Pharmacological studies of plants have suggested that Calendula extracts have antiviral and anti-inflammatory properties. In herbal medicine, Calendula in suspension or tincture is used topically to treat acne, reduce inflammation, control bleeding, and soothe irritated tissue. Limited evidence suggests that Calendula cream or ointment is effective in treating radiation dermatitis.

Calendula has been used traditionally for abdominal cramps and constipation. In experiments, the aqueous-ethanolic extract of Calendula officinalis flowers was shown to have both spasmolytic and spasmogenic effects, thus providing a scientific rationale for this traditional use. However, ingestion of the plant in large quantities should be done with caution as it can potentially become toxic.

Also, its ingestion should be avoided during pregnancy since the necessary studies have not been conducted and allergic reactions have been observed.