Fact check: No, sunflowers don't face each other to 'share energy' in cloudy weather
Bayliss WagnerThe claim: Sunflowers face each other to 'share their energy' in cloudy weather
You are my sunshine,
My only sunshine,
You make me happy,
When skies are gray
This song, first recorded by country singer Jimmie Davis in 1940, is heard often in the U.S. and is often sung as a lullaby.
A meme circulating on Facebook claims that some plants may give deeper meaning to the lyrics. Atop a photo of two mature sunflowers facing each other, almost touching, it says sunflowers turn to face each other when clouds cover the sun so they can "share their energy."
"Sunflowers follow the sun," says a May 12 Facebook post. "But did you know ... When it's cloudy and gray they face each other and share their ENERGY. Imagine if we did this too."
More than 4,000 people had shared the meme a week after it was posted in two popular Facebook gardening groups in mid-May, though one later deleted it.
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On a post in the "Creative Gardening" group, some commenters expressed amazement, but others were skeptical.
"I love sunflowers, and cute thought, but not true," one commenter said.
That's correct. Sunflowers do not turn to face each other.
USA TODAY reached out to users who posted the meme for comment.
Sunflowers dictated by circadian rhythm
According to Stacey Harmer, a professor in the Department of Plant Biology at the University of California-Davis, it is not possible for sunflowers to exhibit this behavior. Harmer and the rest of her team grew sunflowers and examined the plants' orientation toward the sun for a study published in Science magazine in 2016 and detailed on UC-Davis's website.
Harmer said young sunflowers – ones that have not bloomed yet – are famous for bending from east to west over the course of each day, following the movement of the sun (a tendency called "heliotropism" that many plants share).
After a couple of days, they learn to anticipate this movement, bending from west to east at night so they can absorb the maximum amount of sunlight when the sun rises in the morning. This is because they have an "internal clock" called a circadian rhythm, similar to the circadian rhythms that regulate sleep and wakefulness in humans.
"They're anticipating the position and the timing of sunrise," Harmer said.
Science News posted a video documenting this behavior on itsYouTube channel, using footage taken by Harmer's team.
By putting sunflowers under light sources that do not move, Harmer and her team found the pattern holds for around 48 hours. Unless the weather is overcast for several days in a row, sunflowers will continue their normal movement patterns.
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In sustained cloudy weather, sunflowers will eventually "forget" those learned rhythms, Harmer says. But they do not grow toward each other. Instead, they grow straight upwards, against the force of gravity.
The photo in the meme showing two flowers facing each other is also misleading, she says, because mature flowers, which face eastward when grown in sunlight, do not bend at all.
"By the time the flowerhead is ready to open, the stem has stopped elongating, and that means that the plant can't bend anymore, because it's not growing. So there's no way for a flower to change position and face another flower once it is open," she said.
Our rating: False
We rate the claim that sunflowers face each other to "share their energy" in cloudy weather FALSE, based on our research. Sunflowers are regulated by circadian rhythms that orient them toward sunlight. In the absence of sunlight or moving sources of light, sunflowers grow straight upwards, rather than turning toward each other.
Our fact-check sources :
- Stacey Harmer, May 18, phone interview with USA TODAY
- Science News via Youtube, Aug. 4, 2016, Young sunflowers follow the sun's rays
- Science, Aug. 5, 2016, Circadian regulation of sunflower heliotropism, floral orientation, and pollinator visits
- UC-Davis College of Biological Sciences News, Aug. 4, 2016, Sunflowers Move by the Clock
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Our fact check work is supported in part by a grant from Facebook.
