In fact the motor cells in the stem below the head of the sunflower only perform this action up until the flower head forms... thus sunflowers are best photographed in the morning when the rising sun shines onto them from the east. I had observed this in France for the past few summers without realising why... and was usually frustrated in the afternoons as the blooms still faced east... at which time the best photographs were usually of their rim-lit petals.

The English poet Thomas Moore (1779-1852) wrote,

”As the sun-flower turns to her god, when he sets,
The same look which she turned, when he rose”

...which does not appear to be true because the pulvinus, a flexible segment of the stem just below the bud, stiffens after the budding stage and the flower head remains facing east throughout the day. The root of the word being “turn” occurs in the French name (for sunflower) tournesol and the Italian girasole.

And from another English poet, John Clare (1793-1864),

”Training the trailing peas in bunches neat,
Perfuming evening with a luscious sweet,
And sunflowers planted for their gilded show,
That scale the lattice windows ere they blow,
Then sweet to habitants within the sheds,
Peep through the diamond panes their gilded heads.”

Yes, the sunflower is certainly noticeable... if only for its tallness which averages around six feet and often reaches nine feet in gardens. Sixteenth century records, where verifiable, list examples reaching 12 meters in Padua, 8 meters in Madrid) and more recently over 8 meters in the Netherlands and Canada. Perhaps it also grows tall in Kansas where it is the State flower.