Globally, there are about 70 species of Helianthus sunflowers that evolved in the Americas. Only three originated in South America; the rest evolved in North and Central America.
About 1000 BCE, western native American people domesticated the annual Common Sunflower, Helianthus annuus. They traded edible seeds eastward and southward throughout North America from southern Ontario and Canada to Mexico. Two and a half thousand years later, in the 16th century CE, European voyagers took sunflower seeds east across the Atlantic Ocean. Annual sunflowers are now grown worldwide in temperate regions as a garden ornamental, for chewable nutritious seeds and the oil extracted from the seeds, for bird feeding, as livestock silage and meal and for industrial applications.
While growing, tall Common Sunflower stems are phototropic — meaning the head faces east in morning and west in evening. How does this circadian-like rhythm happen? The cells on the east side of the stem elongate in the warm morning sun, so the stem turns to follow the sun. Later in the day, cells on the other side of the stem elongate and catch up, turning the top developing flowerhead back east before morning. After the stem reaches maximum height, most flowerheads face east. Rising sun warms east-facing flowers early so they attract more pollinators. Whole fields of sunflowers face the same easterly direction and make wonderful sights and photos.
In the Asteraceae family, the original daisy-like wild Common Sunflowers have several flowers atop tall branching stems. Selected varieties have been developed to produce one large round flowerhead with a central disk surrounded by bright yellow ray flowers and thin strap-shaped extensions called ligules. Large black oilseed sunflowers were developed for more oil, while the striped confection seed variety was created for birdseed and human snack food.
Seeds germinate best above 50 degrees and when planted 2 inches deep in pre-irrigated soil. Seeds germinate in 7 to 10 days. In a garden, homeowners can thin sprouted sunflowers as soon as the second set of leaves appear. Gently and quickly replant sprouted seeds about 2 feet apart and water immediately. Be careful not to damage the delicate roots.
Sunflowers start to flower after about 80 days. Once flowers fade, seeds may take another month to develop and mature. Sunflowers make long-lasting cut flowers in a vase. Unless wanting to harvest seed or leave it for the birds, dying plants can be removed after flowers fade. Some homeowners plant sunflower seeds at monthly intervals to extend their flower season.
An extensive, deep branched root system helps drought-tolerant sunflowers absorb soil moisture and nutrients. Sunflowers need soil nitrogen, phosphorous and potassium, so are usually alternated with other commercial crops in different years and seasons.
In 2019 the U.S. price of oil-type sunflower seeds was around $16.10 per cwt and confection-type seeds about $21.60 per cwt. The old-fashioned centum weight (cwt), or hundredweight, is an English imperial weight still used as a U.S. unit for shipping. Globally, the standard is metric tons (MMT). Unfortunately, the U.S. population is slow to accept global standards. The U.S. has about 333,546,000 people, equivalent to about 4.25% of the total world population, ranking the U.S. number three by population.
Globally, oil-type sunflower harvest was about 1.1 billion pounds in 2019. In the U.S., about 1.7 million acres of sunflowers are grown; about 89% is in oil-type sunflower. The U.S. is the world’s top oilseed producer, with about 85 million pounds exported in 2019. Canada and South Korea import the most U.S. sunflower kernels. Spain, Mexico and Israel are the largest importers of America’s in-shell confection seed. Global sunflower seed production is about 51 million metric tons (MMT). Europe’s sunflower seed production, 9.7 MMT in 2018-19, is increasing in Ukraine and steady in Russia.
Up to 47 insect pollinators species visit sunflowers, including bees, wasps, ants, beetles, moths and butterflies. All are critically important for pollinating human crops. Only a few insects are “bad bugs” harmful to cash crops. In a home garden, resident breeding birds and other small predators can take care of most pest insects although most are beneficial pollinators.
Jane Weber is a professional gardener and consultant. Semi-retired, she grows thousands of native plants. Contact her at firstname.lastname@example.org or phone 352-249-6899.