Wednesday Weed – Sunflower

Sunflower (Helianthus annuus)

Dear Readers, you may have read about how the bird-sown sunflowers in my garden cheered me up last week. I’ve subsequently become even more fascinated with them, with their geometrical patterns, their usefulness to both pollinators and humans, their rhythms and the way that they have inspired artists.

First things first. The sunflower that we know comes originally from North America, where it was planted on the north side of fields by some Native American groups as the ‘Fourth Sister’ to the more well-known ‘Three Sisters’ of squash, corn and beans. The seeds are extremely nutritious, and the oil that can be extracted from them is high in Vitamin E and low in saturated fat. The birds in my garden have been somewhat spoiled with their diet of hulled sunflower seeds, and now turn their beaks up at anything else. They are delicious for humans too, and I can recommend using them as a sprinkle on salads if they are toasted and given a few dashes of soy sauce.

What about that seedhead, though?

The head of a sunflower is not composed of one big flower, but of a myriad tiny ones, arranged in a series of interlocking spirals. These are called ‘disk florets’ (the ‘petals’ are called ‘ray florets’). In the photo below, you can see some tiny actual petals protruding. Each one of the disk florets will, if pollinated, become a sunflower seed.

A closer view of the fused petals of each disk floret

Each floret is orientated towards the next one at an angle of approximately 137.5 degrees – this is known in geometry as the ‘golden angle’, and it results in a series of spirals that are successive Fibonacci numbers.  At this point my head explodes (maths not being a strong point) but for those of you who are fascinated by these things, here’s a diagram. Note that each number is the sum of the two previous ones (so 1+1 =2, 2+1 = 3, 3+2 = 5 etc). What it actually means is that each disk floret is at a slightly different angle to the one next to it, so the florets are packed in as tightly as it is mathematically possible for them to be. This maximises the amount of seeds that the plant will eventually produce.

The marriage of mathematics and nature can produce some truly beautiful offspring.

Photo One by By 克勞棣 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=38708516

A diagram of a Fibonacci spiral (Photo One)

And now to another feature of sunflowers. It is often believed that the sunflowers follow the sun: that is, they are heliotrophic, following the path of the sun through the sky. However, this is not absolutely true. Sunflower buds start in the morning facing the rising sun, and end it facing west (at least in the Northern Hemisphere), a movement synchronised by the sun (though it will continue in cloudy weather or if kept in constant daylight).

However, the ‘adult’ flowers always face east, towards the rising sun, as shown in the photo below: here, you can see the sun blazing away behind the flowers.

Photo Two by By shirleybolling2005 - Flickr: D40 726, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=21999817

Sunflowers facing away from the late afternoon sun (Photo Two)

The most likely reason for this is that it warms up the plant early in the morning,  and helps it to attract more pollinators. The sunflowers in my garden are visited by carder bees, hoverflies, and honeybees, to name but a few.

Carder bee on sunflower

In addition to their use as a food/oil crop, sunflowers can be used for phytoremediation (removal of dangerous chemicals from the soil) and rhizofiltration (removal of radioactive material from water). Sunflowers were used to remove strontium-90 and caesium-90 from a pond after the Chernobyl disaster and have been used in a similar way following Fukushima. It seems that all of nature is trying to rebalance and clear up our mess.

Because of their ease of cultivation, sunflowers are often the first thing grown by children, and some schools have sunflower-growing competitions. The plants in my garden are a modest metre tall, probably because my plot is north-facing, but in  2016 Suttons Seeds ran a competition for the tallest sunflower. The winner was Valerie Briggs, with a 4.60 metre plant.

Photo Three from https://hub.suttons.co.uk/blog/general/tallest-sunflower-competition-2016

Valerie Briggs’s award-winning 4.6 metre tall sunflower (Photo Three)

When I look at a sunflower I can never work out what came first. Did we look at a sunflower and decide that that was what the sun looked like, or did it happen the other way round? After all, the sun is a bright ball in the sky without any ‘petals’, but many children draw the sun exactly like a sunflower head.

Child’s drawing of the sun and a bird (Public Domain)

However, what is clear is that the sunflower has inspired many artists of all ages and degrees of talent. Van Gogh, of course, painted them during a time of rare optimism  while he was waiting for the arrival of his friend, the artist Paul Gauguin. Newly invented pigments meant that he could experiment with different shades of yellow and ochre, and he went at it with enthusiasm, as shown in this letter to his brother Theo:

I’m painting with the gusto of a Marseillais eating bouillabaisse, which won’t surprise you when it’s a question of painting large sunflowers.”

Vase with Fourteen Sunflowers (Vincent van Gogh , 1888) (Public Domain)

Van Gogh thought of the sunflower as being ‘his’ flower:

“It’s a type of painting that changes its aspect a little, which grows in richness the more you look at it. Besides, you know that Gauguin likes them extraordinarily. He said to me about them, among other things: ‘that — … that’s… the flower’. You know that Jeannin has the peony, Quost has the hollyhock, but I have the sunflower, in a way.”

Vase with Twelve Sunflowers (Vincent van Gogh 1888) (Public Domain)

In return, Gauguin painted Van Gogh painting sunflowers:

Vincent van Gogh Painting Sunflowers (Paul Gauguin, 1888) (Public Domain)

I like to think of sunflowers as being a source of happiness for Van Gogh, a man who had vanishingly few good times in his troubled life. There is something about them that always makes me smile, for sure. Maybe it’s because they are so much bigger than most members of the daisy family, and make me feel correspondingly smaller and more childlike. Maybe it’s that buttery colour, and their complicated relationship with the sun. But for me, it’s also because there seems to be something dogged about the plant, something that is determined to keep going up and up. It’s conjured in this poem by Frank Steele. I hope you enjoy it.

Sunflower

You’re expected to see
only the top, where sky
scrambles bloom, and not
the spindly leg, hairy, fending off
tall, green darkness beneath.
Like every flower, she has a little
theory, and what she thinks
is up.   I imagine the long
climb out of the dark
beyond morning glories, day lilies, four o’clocks
up there to the dream she keeps
lifting, where it’s noon all day.

Photo Credits

Photo One by By 克勞棣 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=38708516

Photo Two by By shirleybolling2005 – Flickr: D40 726, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=21999817

Photo Three from https://hub.suttons.co.uk/blog/general/tallest-sunflower-competition-2016

 

 

 

7 thoughts on “Wednesday Weed – Sunflower

  1. P.D. Crumbaker

    Vivienne. What a totally lovely thoroughly satisfying read. From one delight to the next. I love how you’ve expanded your posts to cover the physical universe and the universe through the lens or artists and writers.

    Reply
    1. Bug Woman Post author

      You’re right, I learned it as phototropism as well. I guess that photo means ‘towards the light’ and helio means ‘towards the sun’, so maybe the latter is just a little more specific?

      Reply
  2. Toffeeapple

    More teaching, thank you! I had noticed, many years ago in France, mature Sunflowers facing east and now I know why; you are a remarkable tutor and I am very pleased that I found you.

    Reply

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