The giant garden sunflower is related to the native annual sunflower that was first cultivated by American Indians for its edible seeds and for its use in bread flour and as oil to season food and anoint hair.
Natural sunflowers are only a few inches in diameter, but cultivated varieties sometimes exceed a foot across. The plants easily grow to 8 or 9 feet tall. The flower head, made up of hundreds of small, brown disk flowers, is surrounded by yellow ray flowers.
Although flowers normally serve to produce seeds, the ray flowers are sterile; their only function is to attract insects. So the disk flowers attend to pollination and seed production.
The flower heads with their bright yellow ray flowers all face east. Many people believe that sunflowers twist their stems to face the sun all day, but as Anna Comstock wrote in her “Handbook of Natural Study” in the early 1900s:
“This belief shows the utter contentment of most people with a pretty theory. If you believe it, you had best ask the first sunflower you see if it is true, and she will answer you if you ask the question morning, noon, and night.”
Green plants are phototropic and respond by growing toward the source of light. But once the flower opens, it no longer turns toward the source of light, and the heads of the sunflowers will face east the whole day.
Jim Gilbert’s Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.