Sunflowers are impressively large. They are probably one of the few flowers–hollyhocks being another–that can frequently be taller than you are–sometimes much taller. These members of the aster family are fast-growing annuals and perennials; some of them can reach 15 feet.
If you are used to seeing sunflowers growing in rows or bunches at the back of flowerbeds, then it is a bit of a shock to see fields of them stretching away into the distance when you first stumble upon a commercial planting of them. Sunflowers (Helianthus annus) were cultivated first by the tribal peoples of the Great Plains.
Lewis and Clark wrote of seeing them growing and in use. Archeological evidence indicates they were domesticated and subjected to selective breeding for over 5000 years. Early Spanish explorers of the Great Plains brought the seeds back to the Old World where they became a commercially cultivated crop, initially in Russia, and then throughout Europe. By the early 19th century, as Lewis and Clark walked across the northern Great Plains, witnessing the aboriginal cultivation and use of the plant on its native ground, commercial cultivation in Russia was reaching 2 million acres.
For the first several hundred years of its European sojourn the sunflower was largely grown as an ornamental. In 1716 an English patent was approved for the extraction of oil from the seeds. By the late 18th century commercial cultivation for oil production was in full swing. In addition, to oil production though, another variety was grown for direct consumption of the seeds.
In the late 19th century the sunflower returned to the US from Russia as a commercial crop. The Canadian government took the sunflower quite seriously and began a breeding program in 1930. Through the 20th century the popularity of sunflower oil increased and consequently so did the amount of acreage under cultivation, spreading down from Canada into Minnesota and North Dakota.
The first place that I can recall seeing sunflowers grown commercially was in Germany. In addition to sunflower oil, the Germans are quite fond of grinding up sunflower seeds into a meal and adding it to bread.
The German fondness for incorporating sunflower meal into bread as spread over the decades into neighboring European countries and is not unknown in the United States.
The mammoth nodding heads of sunflowers (which, most people know, get their name from their heliotropic habit) are not actually single flowers at all. In fact, each ostensible “flower” is composed of two types of blossom. Each apparent petal is actually a single sterile “ray flower,” the primary of which is to collectively attract insects and other pollinators. The “disk flowers,” which fill the region inside the ring of ray flowers are the sexual organs of the plant. Each tiny flower holds both male (anthers) and female (pistil) organs.
Although they contain both genders, sunflowers are self-sterile; the pollen of a given plant needs to be transported to another plant in order for fertilization to take place. In other words, if you wish to your own sunflowers to breed true to variety, you have to grow them several miles from other varieties in order to produce seed that will produce plants that resemble the previous generation. As this sort of geographical isolation is unlikely, you are better off doing the pollination manually.
Manual pollination is done by first insuring that no insect pollination can take place by¬–just before the disk flowers open–covering the selected flower heads with a bag made of porous material (air should circulate and moisture be allowed to escape in order to avoid mold). After the flowers open and the anthers have emerged, you can brush the pollen off of them into a plastic bag with a paintbrush. Take this pollen to a second plant, dust the pollen off the anthers of that plant into a second bag, and then brush the pollen from the first plant onto the pistils of the second. Repeat the pollen transfer process, brushing the pollen from the second plant onto the flower of the first.