Marigold refers to flowering plants of the genus Tagetes. The marigolds belong to the family Asteraceae of the plant kingdom. Marigold plants are quite common around the world and are often grown as ornamentals in India. Although a native of the America, marigold is a very easily cultivable flower crop, grown around the world. Three species of marigolds, namely, Tagetes erecta, Tagetes patula and Tagetes tenuifolia are cultivated more commonly than the other species. This tutorial discusses the characteristics of marigolds in detail, along with their common uses.
Marigolds are recognised by their prolific yellow-red inflorescence of composite flowers with ray and disc florets, which are usually tightly clustered, giving most marigolds a pompom-like appearance.
The ray florets are constituted by the more obvious petals usually yellow-red coloured, while the disc florets are more columnar and difficult to spot.
The leaves are pinnately compound, lanceolate and serrated. The florets are either bilabiate or quilled.
The length of the plant varies between 0.1 to almost 2 meters, and the flower heads usually spread to about 1 to 4-6 cm.
Marigold grows well in a mild climate and adapts well to different soil conditions and even conditions of drought.
Marigold belongs to the genus Tagetes of the family Asteraceae. The name of the genus was given by Carl Linnaeus in the year 1753. The name of the genus originates from the name of the prophet Tages, who’s regarded as the founder of the Etruscan religion. The botanical classification of marigolds is as follows −
Kingdom | Plantae |
|---|---|
Phylum | Magnoliophyta |
Class | Asterids |
Order | Asterales |
Family | Asteraceae |
Genus | Tagetes |
Species | T. erecta, T. patula, T. tenuifolia, etc. |
Marigold comprises around 50 species, the three most commonly cultivated varieties of which have been listed below −
Tagetes erecta (African marigold)
These species are more tolerant toward dry summer climates than the French marigolds. They are taller (12-14 inches) and with larger blooms (3-5 inches).
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Tagetes patula (French marigolds)
The flowers of French marigolds are smaller (diameter ~2 inches) than those of African marigolds. The petals are frilled, unlike those of African marigolds.
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Tagetes tenuifolia (Signet marigold, “Lemon Gem”)
Unlike the African and French marigold species, the signet marigold possesses only one flower instead of a composite inflorescence. The species is also smaller than the other two types.
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Marigold is found to grow well in mild climates, within a temperature range of 14-28° during the growth period, which promotes luxuriant flowering.
Generally, under favourable environmental conditions, marigolds can be grown around three times a year across three seasons- the rainy season, the winter season and the summer season.
Marigold grows optimally in sandy loam soil, although it is found to grow quite well in other types of soil too. The general requirement is that the soil must have good water holding capacity (WHC), and apH of 7-7.5, along with being fertile and friable.
Typical NPK fertilizers in the ratio of 200: 100: 100 kg per hectare are used to promote plant growth.
About 1.5kg of seeds are enough for planting in an area of 1 hectare.
Once the seed germinates into a seedling and further into a plantlet, it is transplanted. This usually takes about a month from the time of sowing.
A common practice that helps promote lush growth and flowering in marigolds is that of pinching- a method of pruning by literally pinching off the plant at the top above a node.
Weeding must be done regularly, around 4 sessions of weeding are required during the growth period of marigolds.
A summarization of the sowing and transplanting patterns adopted for marigolds is given in the table below −
| Flowering season | Time of sowing | Transplanting time |
|---|---|---|
Rainy | June | July |
Winter | August | September |
Summer | January | February |
Widely regarded as an ornamental plant, marigold is popularly grown in gardens and also used in decor and for making garlands.
Although most species are not usually considered edible like some other members of Asteraceae, the medicinal properties of marigolds are widely appreciated. Its medicinal properties are by the brightly coloured flowers- they store various essential oils and resins.
Marigold extracts are used to treat skin-related problems such as contusions, bruises, sunburns, inflammations and injuries. It's proven helpful in treating eczema as well.
Tagetes minuta possesses antibacterial activities that prove beneficial for skin health.
Marigold is also proposed to treat cancer- the flavonoids present in marigold exhibit cytotoxic and inhibitory actions against cancers of colorectal and melanoma types.
Carotenoids and flavonoid extracts show anti-inflammatory action.
Carotenoids are anti-oxidants, with a beneficial effect on ocular health.
Marigold are also thought to relieve menstruating women of their abdominal cramps.
The pigments extracted from the flowers are used in manufacturing dyes, used in textile industries and also food industries.
The volatile oils and antioxidants impart insecticidal and nematicidal properties.
Marigolds are a group of brightly coloured flowering plants that belong to the genus Tagetes of the family Asteraceae, the same family as the sunflower. The bright yellow-orange to red inflorescence of composite flowers is the most distinguishing characteristic of the flowering herb. Marigold has around 50 species, however, only 4 of them are commonly cultivated. The commonly known varieties of marigolds are the African marigold, the French marigold and the signet marigold. Marigolds are easily cultivable and although native to America, it is widely grown in many parts of the world, including India. Different types of marigolds possess anti-inflammatory, antioxidant and antibacterial properties. The carotenoids and xanthophylls are also used as colourants in the textile and food industries.
Q1. What is meant by the term “composite flowers”?
Ans: Composite flowers refer to an inflorescence in which several flowers (known as florets) group together to form a single flower, like a pseudanthium.
Q2. Is Calendula spp. the same as marigolds?
Ans: The name marigold is also associated with the genus Calendula, as Calendula spp. are commonly referred to as pot marigold. They do belong to the same family, however, they are a genus different from Tagetes, and have a different inflorescence as well.
Q3. What are some of the diseases that marigolds are susceptible to?
Ans: Marigolds are prone to bacterial and fungal diseases such as wilt, botrytis flower blight, root rots, and leaf spots. Leaf burns may be caused due to excess nutrients like boron, molybdenum and manganese.
Q4. Which are the major pigments present in marigold?
Ans: Lutein and zeaxanthin are two carotenoids present in marigolds, imparting to the plant its characteristic yellow colour and also anti-inflammatory and antioxidant properties.
Q5. What compound, characteristically occurring in citrus fruits, is present in marigolds and acts as an insect-repellent?
Ans. Limonene is an organic compound found in marigolds, which is known to repel insects like whiteflies, from infesting plants like tomatoes.
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