Reprinted from The Environmentor, vol. 10, no 6, pp. 17-18
Sunflowers have come to our attention as a symbol of Ukraine's resistance to Russian invasion. You can plant some along a fence row to enjoy their bright flowers and maybe their tasty seeds — if you can get there before the goldfinches.
Why do sunflowers follow the sun?
Collections of classical Greek mythology offer the story of Clyte, a water nymph who fell in love with the Sun God Helios. Unfortunately Helios had no interest in her, and instead he pursued princess Leucothea, the daughter of a Persian king. When Clyte learned that Helios had disguised himself as the queen mother in order to sneak into the princess' room, she was so jealous that she told the king. Sure enough, the king was furious! He was so outraged that he ordered his daughter buried alive. Clyte hoped that with the princess out of the way, Helios would be hers. Instead, Helios wanted nothing to do with her. She pined and moped, not eating or drinking, just staring at the Sun all day, hoping he would notice her! But he totally ignored her.
The myth says that after nine days she was transformed into a plant, with a golden flower that not only looks like the sun but even spends the day watching the sun as it travels across the sky: the sunflower Helianthus annuus.
Do sunflowers really follow the path of the sun? How do they do it? They have no eyes to see.
And why would they bother? They are not lovesick nymphs!
In fact, it's only the young plants that pivot their flower heads from east-facing in the morning, to west-facing by sunset, during the night turning back east again. In a field of mature sunflowers, however, you'll find essentially all the flower heads facing east -- all day.
Helianthus annus is in the Composite family. Each flower head is composed of hundreds of tiny “disk” florets arranged in famous Fibonacci spirals, surrounded by a ring of petal-bearing “ray” florets. If pollinated, each floret can become one seed.
The plant moves the young flower head by growing faster on one side of the stem than on the other. Growth genes on the east side of the stem become active in the morning, pushing the flower head around until it faces west. The west side genes turn on in the afternoon, pivoting the head back. Light sensing molecules and built-in circadian (24hr) timer mechanisms control the activation of the genes. Once the florets start to mature however, this cycle stops and the flowerhead just faces east.
Why? (In scientific terms, what's the benefit?)
Scientists find that pollinator insects pay more visits to sun-warmed blooms. So the tracking behavior keeps the flower head facing into the sun, warmly inviting pollinators.
There are a few Helianthus species in Africa, but all the other species of the genus (including H. annuus) are native to the western hemisphere. Frankly I'm puzzled that there's a “classical Greek myth” about a plant that didn't reach Europe until the 1500s! Might the story be a Victorian confection, contrived to parallel other stories of hapless maidens who were turned into plants? (BTW, Helios tried to bring his beloved princess Leucothea back to life, but failed. So he turned her into the frankincense tree!)
Once sunflowers reached Europe, they were admired as ornamental plants and then valued for their seeds and oil, especially in Ukraine where sunflowers were so common that they became an unofficial national symbol. But it wasn't until the Russian attack on Ukraine that the sunflower became a symbol of resistance. A February 24, 2022 video showed a Ukrainian woman telling Russian soldiers to keep sunflower seeds in their pockets “So that flowers will bloom where you die.”
Mythology: timeless tales of gods and heroes – Edith Hamilton p 291
with video of young sunflower plant
Circadian regulation of sunflower heliotropism, floral orientation, and pollinator visits https://www.science.org/doi/10.1126/science.aaf9793
What to Know About the Meaning of Sunflowers in Ukraine