Facts About Sunflowers

The sunflower's leaves and buds track the sun.

The sunflower's leaves and buds track the sun.

The sunflower is an annual flowering plant and a member of the Helianthus genus. It produces a branched taproot that penetrates the soil up to 6.5 feet and produces a flower head that carries over 500 seeds. Sunflowers grow quite tall. The tallest ever recorded, grown in the Netherlands, was over 26 feet high. The yellow petals around the flowers’ central disc are known as ray flowers, and when they drop, harvest time is not far behind.


Sunflowers are native to North America and were first spread, cultivated and used by Native Americans. Agronomists and plant geneticists with Purdue University believe the plant began its spread throughout Europe from Spain. In the mid-1800s Russians increased the seeds’ oil content significantly and introduced the new high-oil plants into the United States. Commercial production, for oil, human snacks and birdseed flourished in the Great Plains for some time. The past three decades have shown a decline of sunflower production in that region because of declining prices, insects, diseases and birds.


The sunflower thrives when grown in an arid climate. Although the plant is tolerant of both cold and warm temperatures, it tolerates cold better, as long as temperatures don’t fall below 28 degrees Fahrenheit. Extreme heat causes a reduction in seed oil and affects seed fill. Temperatures between 70 and 78 degrees produce the best flowers and seeds. Although the sunflower flourishes in arid climates, it is not particularly drought-tolerant, especially in the weeks leading up to and after flowering.


The two most important things for the home gardener to do when germinating sunflower seeds are to plant them firmly in moist soil and keep the seed bed weed-free. Sunflower seeds are typically planted in early spring in northern regions; in May in the Midwest and from the middle of March through the first week of April in the south. Plant the sunflower seeds no deeper than 3.5 inches. Plant 1 to 2 inches deep in heavier soils. Water the soil to keep it consistently moist beginning 20 days before flowering and continue until 20 days after flowering. Sunflowers typically form flowers 30 to 35 days after planting.


Sunflower seeds are ready to harvest four months after planting. As the flower heads mature, a battle with birds may ensue. It is not at all uncommon for birds to remove the entire 500 seeds from the flower. Protect the flower heads from birds by placing a brown paper bag, with small holes poked in it, over the flower. When the seeds turn black or gray, they are ready to harvest. Cut the flower from the plant and rub two flowers together. The seeds should easily fall out.

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