La Gravette, Verlhac-Tescou
I stayed for two weeks with my wife’s family in the southern French countryside sandwiched between the aerospace hub, Toulouse, and the shaggy peaks of the Pyrenees. The land is soft and rolling, like rising dough under a piercing summer sun. The forest has been reduced to pockets of cool besieged by radiant fields of sunflower, or in the flatter areas, cleared for wine vines drowsily leaning on wire. It hadn’t rained in weeks, and the soil had no more water to dole out. The grass was the color of toast, darkening by the day, and tree leaves were limply yellow. Only the fields of (rainfed) sunflowers stood tall and defiant. At least until into their old age, when their massive bald heads finally bowed from the weight of their seeds. I enjoyed running past them in the early morning, as the sun seemingly rose from their company into the sky. I wanted to know their origins, how they grow, and what they are used for.

Le Tournesol (Helianthus annuus)
You might say sunflowers are a part of my identity. They are the state flower of Kansas, the birthplace of my Mom, and where much of my family still lives. There they grow wild, natives of the North American prairie. Sunflowers were first cultivated by North American Indians over 3,000 years ago, mostly for their seeds. Through patient breeding by selecting the largest seeds year after year, seed size increased by over 1,000%. The effort had reason, sunflower seeds can be eaten raw, roasted, cooked, dried, ground, and when pressed produce oil. Even the flower buds are edible. North American Indians used the sunflower plant as medicine to heal wounds, dye for baskets, and decoration. Their many useful qualities did not go unnoticed, and sunflowers were spread across the world and coopted into modern agriculture. In 2017, the three largest producers are the Ukraine, Russia, and the E.U.  Outside of garden, they are mostly grown for:

• Human consumption (large seeded white stripe sunflower)
• High quality vegetable oil, for frying, cooking and salad dressings
• High protein meal for livestock feed (hybrid oil types)

Growing Conditions
Sunflowers are both annual and perennial, which have smaller seed heads that flower after at least two years, and grow in clumps with deep roots with tubers and rhizomes attached. As a result, only annual sunflowers are cultivated for agricultural production and gardening. Annual sunflowers grow between 13 and 30 ºC, but optimal temperatures are between 18 ºC and 26 ºC. The ideal is 22 ºC, and each 1 ºC lower decreases the oil content by 1.5%. They are sensitive to frost. Much of sunflower’s appeal comes from their drought resistance. Their ideal precipitation range is 500-800 mm/growth cycle, and can tolerate as low as 250 mm/growth cycle. Sunflowers are most sensitive to water stress during early growth and flowering. Their height means lodging is an issue. The soil should be slightly acidic, deep as well as iron-rich, or calcimorphic (lime-rich). The suggested NPK amount for production in kg/ha per growing cycle is listed below:

N: 50-100
P₂O₅: 45-105
K₂O: 70-150

Good, commercial yield in a rainfed system is from 2.1 to 2.4 tones of seed/ha. In an irrigated system from 2.5 to 3.5 tons of seed/ha. The most commonly reported disease is Phoma black stem, a soil borne fungus. To avoid it and other fungal diseases, sunflower should not follow safflower, cotton, pea, beets, potatoes or alfalfa. Generally, it is rotated on the same field every 4 to 6 years (Sys et al. 1993). 

Phenology
The total time between germination and harvest varies mostly depending on the accumulation of temperature units above the minimum requirement (degree days or GDD) and the genetics of the sunflower plant. Other factors include planting depth, soil water content, soil type etc. Generally, similar to most annual crops, it takes around 5 months (150 days) until physical maturity. The lifecycle of the sunflower can be broken up into distinct phases that correspond with degree days, the most important are below: 

• VE: (144 GDD) The seedling has emerged and the first leaf is less than 4 cm.
• V (1, 2, 3, etc.): (504 GDD) This is determined by counting the number of true leaves.
• R5: (894 GDD) The beginning of flowering. 
• R9: (1,283 GDD) Physiological maturity, the bracts become yellow and brown.

Harvesting
Not all varieties ripen unevenly, and seeds can be lost from shattering, reducing yield. At this stage birds become a significant pest, especially if the heads face upwards. As a result, it is best to cut the crop early, when the back of the head is yellow, and the center of the flower brown (R9). To dry the seeds, the seed heads are cut and piled in the field for one or two weeks until dry. Often on large farms this is not feasible, and instead farmers use a process called desiccation. They spray herbicide, such as glyphosate, to artificially speed up and even out the drying process on the field, increasing yield and lowering drying costs. 

Sunflower Seed Oil
Sunflower oil has polyunsaturated and unsaturated fatty acids, which include omega-3 and omega-6 fatty acids, vitamin E, but no cholesterol. Research is mostly going into modifying the fatty acid profile of sunflower oil to enhance its functionality, for example ‘high oleic’ sunflower oil, which has increased monounsaturated fatty acid. As a result, it has higher stability during frying. 

Sunflower seed cake The sunflower seed cake is used for low-grade fertilizer, and animal feed. Its high-protein content means it can be used as a substitute for soybean meal to feed both monogastric and ruminant livestock. Listed below is the nutritive value of various levels of sunflower seed cake according to different levels of processing. 

• Meal from unhulled seeds 28% protein and 25-28% fiber
• Meal from partially dehulled seeds 35-37% protein and 18% fiber
• Fully dehulled seeds 40-42% protein, and 12-14% fiber

Before the seedcake can be used, it must be dried first. 

Sunflower Seed Oil Production
This is a multi-step process that results in oil and seed cake.