This genus of the daisy family includes one of the most important oilseed plants in the world. It is also used for livestock fodder, as well as the Jerusalem artichoke with edible tubers, and many ornamentals. Consisting of around 70 species of annuals and perennials, all native to the Americas, they have large daisy-like, usually golden-yellow flowerheads, which are on prolonged display from summer to autumn. The plants have hairy, often sticky leaves and tall, rough stems.
Sunflower is a short-season plant classified under the family Asteraceae and the genus Helianthus with more than 70 species known worldwide. Sunflower is famous for its rotation around the sun. It ranked the third most important oilseed crop after soybean and rapeseed.
Helianthus annus
It is known as a common sunflower that is a fast-growing and upright plant. It is a large daisy-like yellow flowerhead with brown centers borne in the summer. It is an oilseed crop native to North America. It is cultivated throughout the world and most of its products have been commercialized as culinary or livestock feed.
They are tall, leggy plants with broad and mid-green leaves. This species produces one of the most important oilseeds in the world. It can be a little large for small gardens, but newer varieties have been developed that grow to a more manageable size that is about 6 inches. The varieties include ‘Autumn Beauty’ with medium-sized flowers usually brownish red, deep red, light yellow or golden yellow, whereas, ‘Teddy Bear’ is a compact grower with double and dark yellow flowers.
Moreover, sunflowers symbolize solar deities, power, nuclear non-proliferation, longevity and mortality. It gets its common sunflower as its flower can “track” the sun, which is known as heliotropism. This is due to the presence of plumule (a light-sensitive organ) that is located at the tip of the stem. Heliotropism helps sunflower to capture as much sunlight as possible for growth and development. However, they stop tracking the sun when they start to flower and the heliotropism is controlled by a plant growth regulator known as auxin.
Helianthus decapetalus
This thin-leaf sunflower is a strong-growing perennial from central and southeastern USA that grows up to 5 feet high. The leaves are smooth above and hairy underneath and are lance-shaped. The flower heads are yellow with yellow-brown centers and up to 3 inches in diameter, which appear in summer and autumn. ‘Maximus’ is a popular cultivar of thin-leaf sunflower.
Helianthus maximilianii
This perennial species has rough stems densely covered with 8 inches long and spearhead-shaped leaves can grow to at least 10 feet tall. Golden-yellow flowers that range about 4 to 6 inches formed across appear in summer and fall.
Helianthus x multiforus
Helianthus x multiforus is a clump-forming perennial to 6 feet in height and 3 feet in spread. The domed flowers can be up to 6 inches across and appear in late summer to mid-autumn. Popular cultivars of this species are ‘Capenoch Star’, ‘Loddon Gold’, ‘Soleid d’Or’ and ‘Triomphe de Gand’.
Helianthus salicifolius
It is also known as Helianthus orgyalis is an upright perennial that is valued for background planting for landscaping. It can grow to 6 feet high and bears brilliant yellow with 3 inches wide and single daisy-like flowers on branching stems in late summer or autumn. The rich, dark green and shiny leaves are willow-like and look good planted with late-flowering blue asters or salvias.
Helianthus tuberosus
This species is commonly referred to as Jerusalem artichoke. The ‘artichoke’ in the common name of this sunflower relative comes from a fancied resemblance in flavor of its edible tubers to those of the true artichoke (Cynara scolymus); the ‘Jerusalem’ has resulted from a mishearing of the Italian for sunflower, girasole. It is native to USA and Canada, it is sometimes regarded as a weed as it spreads rapidly and makes a forest of slender stems terminating in small yellow flowerheads. A popular vegetable in some parts of Europe, it is not always realized that the tubers contain the carbohydrate inulin, not used by the human digestive system, therefore having little food value. Native Americans fermented the tubers in pits, converting inulin to digestible sugars.
Horticultural practices, pest, disease and postharvest management
Sunflowers can be planted as ornamental pot plants. Sunflower is a perennial herb that reaches a height of 1.5 to 2.5 meter with a strong and ramified stem. The flower heads can have an average diameter of 10 to 40 centimeter and consist of several hundred seeds. Commonly, the seeds are about 0.8 to 1.7 centimeter long and 0.4 to 0.9 centimeter wide depending on the varieties and environmental factors. The asymmetrical seed is flat and the color can vary from black to vertical black-and-white stripes to white, depending on the sort. There is a thin layer of wax found on the seeds to protect them from evaporation.
Apart from that, sunflowers are frost-hardy plants and they prefer full sun and protection from wind. Sunflowers adapt to different climatic soil conditions has enhanced their cultivation The soil should be well drained. Fertilization has to be taken place in spring to promote large blooms and water generously in dry conditions. Sunflower cultivation requires low moisture compared to other cereal crops for survival due to its long taproots for the absorption of soil water during drought. Perennials should be cut down to the base when they finish flowering. The plants can be propagated from seeds or by division in fall or early spring.
Sunflowers can be incorporated into local cropping systems, enhance soil health and increase biodiversity in a crop rotation system. It does not require high levels of fertility like other cops as they have strong adaptive mechanisms in growing in complex environments.
Sunflower cultivation usually faces several pests and diseases. Commonly, sunflower moths, weevils as well as stem borers are found the major pests throughout the cultivation period. Deep ploughing can be conducted after harvesting to expose the pupal stage of the pest. Then, some common infestations are downy mildew, boomrape, white rot, stem canker, Alternaria blight, rust, Phoma black stem, Fusarium wilt, charcoal rot and Rhizopus head rot. Biofumigation such as the use of Brassicaceae can be used to protect the sunflower crops.
The harvested seeds have to be stored cool and well-ventilated after drying until further processing to avoid the formation of yeast that causes an awful smell during storage and transportation. Proper storage with a low relative humidity of the storage environment can be used to ensure the prevention of postharvest contamination with aflatoxigenic mold.
Nutraceutical value and downstream products
Sunflower is one of the important oilseed crops grow throughout the world as a source of premium vegetable oil, dietary fiber and protein (make up about 85 % of the total protein content). Sunflower seeds have an oil content of between 44 and 47%. The hull, which is the outer layer of the seed, makes up about 30% of the seed and does not contain any oil. When the hull is removed, the remaining seed, known as dehulled sunflower seed, has an oil content of more than 60%. This is because the hull contains very little oil, so removing it leaves behind the oilier kernel.
On top of that, research has found that sunflower seeds possess antidiabetic, antimicrobial, antihypertensive, anticholesterol, antitumor, anticancer, antihypoglycemic, antiasthmatic, anti cardiovascular as well as antioxidant properties. It also helps against inflammation.
Sunflower contributes about 87 % of vegetable oil production, making it an economical and promising oilseed crop. Its yield can be explored maximally as an alternative to the existing oil crops such as palm oil, palm kernel oil soybean, rapeseeds and peanut if properly harnessed. After pressing, the resulting press cake is extracted by solvent and the raw oil has to be refined and winterized to remove unpleasant compounds and aroma as well as the waxes found on the hull. The oil is a light amber oil coloration and neutral in taste, which can be used for a wide range of applications in various industries.
Sunflower oil is classified as a non-volatile oil. The major compositions of sunflower oil are polyunsaturated linoleic acid and monosaturated oleic acid. Furthermore, sunflower oil contains palmitic acid, stearic acid, carotenoids, tocopherols, tocotrienols and phytosterols as well as excellent phenolic antioxidants (about 1 to 4 % of the total mass chlorogenic acid). Additionally, amino acids such as glutamic acid, aspartic acid, arginine, phenylalanine, tyrosine, leucine, methionine and cysteine are found in sunflower seeds. The oil is rich in vitamins and mineral elements. It can stand on the shelf for more than one year in the market. It is easy accessibility and possesses health benefits. Furthermore, sunflower oil has a wide range of applications in the cosmetic industry due to its water retention and non-inflammable properties.
Sunflower meal is the by-product of the extraction of sunflower oil from the seeds. It is also known as sunflower oil meal, sunflower seed meal, dehulled sunflower meal, un-dehulled sunflower meal and decorticated sunflower meal. Besides, it serves as a great nutritional food and composite meal for livestock that consists of essential amino acids, vitamins B and E, minerals (like calcium, copper, iron, magnesium, manganese, selenium, phosphorus, potassium, sodium and zinc) as well as high antioxidant property.
Sunflower meal can be incorporated as an ingredient in confectionery and bakery products such as bread, tortilla, pancakes, flapjacks, cookies, brownies, muffins, pretzels, pasta, ramen, protein bars as well as cereal and other downstream products. Sunflower seeds can be used as an alternative for biodiesel and it is profitable when there is large-scale production.
Further reading:
Jiraungkoorskul, W. A. N. N. E. E. (2016). Review of nutraceutical uses of an antioxidant sunflower sprout, Helianthus annuus. Asian Journal of Pharmaceutical and Clinical Research, 9(6), 21-23.
Markell, S. G., Harveson, R. M., Block, C. C., & Gulya, T. J. (2015). Sunflower diseases. In Sunflower (pp. 93-128). AOCS Press.
Muhammad Anjum, F., Nadeem, M., Issa Khan, M., & Hussain, S. (2012). Nutritional and therapeutic potential of sunflower seeds: a review. British Food Journal, 114(4), 544-552.
Nguyen, D. T. C., Nguyen, T. T., Le, H. T., Nguyen, T. T. T., Bach, L. G., Nguyen, T. D., … & Van Tran, T. (2021). The sunflower plant family for bioenergy, environmental remediation, nanotechnology, medicine, food and agriculture: a review. Environmental Chemistry Letters, 19, 3701-3726.
Rauf, S., Ortiz, R., Shehzad, M., Haider, W., & Ahmed, I. (2020). The exploitation of sunflower (Helianthus annuus L.) seed and other parts for human nutrition, medicine and the industry. Helia, 43(73), 167-184.
Robertson, J. A., & Burns, E. E. (1975). Use of sunflower seed in food products. Critical Reviews in Food Science & Nutrition, 6(2), 201-240.
