Sunday, August 5, 2012

Sunflowers - Helianthus annuus

I love sunflowers. As a kid, I was enamored with how quickly, and how tall they grew. My dad always had sunflowers in his vegetable garden, and when I asked him why (we never ate them, or anything), he said "The birds and bees like them, and so do I, so I grow them." Sounds like a great reason to me, so I grow them, too.

Here's some fun stuff about our native annual sunflower, Helianthus annuus.

Sunflowers exhibit heliotropism, a plant's reaction to turn to face the sun throughout the day, but once their flowers are pollinated, they stop.
Heliotropism most likely helps to increase the development of pollen -- once pollinated the sunflower head remains facing east.  This daily dance with the Sun results from motor cells in a flexible segment of the stem just below the bud known as the pulvinus. These cells enlarge or shrink according to the turgor pressure of the water against the cell walls. As pressure increases on one side and decreases on the other the stem responds by drooping or stiffening.
According to Purdue University:
Sunflower is one of the few crop species that originated in North America (most originated in the fertile crescent, Asia or South or Central America). It was probably a "camp follower" of several of the western native American tribes who domesticated the crop (possibly 1000 BC) and then carried it eastward and southward of North America. The first Europeans observed sunflower cultivated in many places from southern Canada to Mexico. 
It's the state flower of Kansas.

From the Illinois wildflower site:
Long-tongued bees are the most important pollinators of the flowers, including the honeybee, bumblebees, digger bees (Melissodes spp.), and leaf-cutting bees (Megachile spp.). Short-tongued bees that are important visitors of the flowers include Halictid bees, alkali bees, and some Andrenid bees. Some bees are specialist pollinators (oligoleges) of sunflowers; the oligolectic bees Andrena accepta, Andrena helianthi, Dufourea marginatus, Melissodes agilis, and Pseudopanurgus rugosus have been observed to visit the flowers of Annual Sunflower.
Here's how to roast your own seeds:
Plain sunflower seeds can be roasted at 300 degrees F for 20-30 minutes. If you have a desire for salted seeds, soak seeds overnight in a solution of two tablespoons of salt in one cup of water. Boil the seed and salt solution for a few minutes, and then drain the liquid. Spread the seeds on a flat pan and roast at 200 degrees F for three hours or until crisp.

And here's a way cool thing that appeals to my Math and Computer Science Major mind - Alan Turing, the father of Computer Science, noticed that sunflower seed heads often exhibited a spiral growth pattern using a fibonacci sequence - a mathematical sequence where the next number in a sequence is determined by adding together the two previous numbers,  {0, 1, 1, 2,3,5,8...}. 

He hoped that by studying the arrangement of leaves around the stem, and other growth patterns, (a study known as phyllotaxis), it might help us better understand how plants grow, but he died before he could finish his work.  In honor of the centennial of his birth, the Museum of Science and Industry in Manchester, England sponsored a citizen scientist effort this year to plant thousands of sunflowers, and
"...test the extent to which they follow the Fibonacci rule, to explain why this happens and the reasons why they sometimes don’t. The results will be announced during Manchester Science Festival (27 October – 4 November 2012) alongside a host of cultural events across Greater Manchester to celebrate Turing’s legacy in his Centenary year." 
Erinma Ochu, Project Manager of Turing’s Sunflowers said:
"This is a fantastic opportunity to learn about the wonder of maths in nature. Communities coming together to plant sunflowers around the city and beyond is a fitting celebration of the work of Alan Turing, and they will also provide the missing evidence to test his little-known theories about Fibonacci numbers in sunflowers.”
I wish I had read about that earlier - I might have participated.  I look forward to hearing about the results, at any rate.   In the meantime, I'll just enjoy them, along with the birds and the bees, and remember my Dad.

Update: 8/9/12 - Erinma Ochu, the project manager of the Turing Sunflower Project of Manchester England England (across the Atlantic Sea!)   -  informs us via the comment section that we can still contribute to the effort if we are growing sunflowers.  Just go to this link and register and follow the directions.  I did.


  1. Hello Ray, wonderful post on sunflowers and so glad you like Turing's Sunflowers experiment. If you are already growing sunflowers you can take part - you just need to register the flowers you want to pledge to the experiment on

  2. Thanks so much for commenting, and let me add how cool it is that you noticed us.

    I will definitely check out the link and see what I can do to participate and promote participation with the rest of our audience.

    Exploring a connection with my interests in Math, Computer Science, Horticulture, and Gay issues, while honoring my Dad's legacy is too serendipitous to ignore. Cheers!

  3. I really would love to count a couple. Do we just use the big ones?

  4. I haven't looked at all the details, yet, Mary. So far, I've just registered my name and email. We'll be getting more detailed directions later, I understand. For now, count the petals of the ones you register(ed). If they're already drooping, cut and dry the heads (protect from wildlife) and await instructions. I'll spend some more time at the site and include something on an MG status if I find out more info. Cheers.