Hmmm - photophobes.

Many plants track the movements of the sun by a process called heliotropism. More plant species orient their leaves than blooms, so they will be perpendicular to the sun's rays at dawn and evening in order to maximize photosynthesis. The flowers of some plants also display the same behavior.

Plants also have internal clocks/rhythms that affect movements (see circadian and endogenous rhythms) and in many cases, the sun tracking continues, compliments of the plant's natural rhythms, even if the light source is eliminated. Many heliotropic plants even turn their heads to the east in total darkness in anticipation of dawn.
Many, if not most people, are under the misconception that the heads of sunflowers track the sun. If you observe a field of cultivated sunflowers, the flower heads face in more-or-less the same direction, but if you look closely at a field of sunflowers in the afternoon, you'll see that the flower heads are mostly facing east, where the sun rises each morning.

Only immature flower buds of the sunflower exhibit true heliotropism, and on sunny days the buds track the sun across the sky from east to west and by dawn the buds will have returned to face eastward, but as the flower bud matures and blossoms, the stem stiffens and solar tracking halts.

Al

Thanks Al. I guess all of my stems have hardened. I must not have noticed them moving before they blooomed.

Melissa

i have a couple of unusual sunflowers this year that sprang up voluntarily from feeding the seed over the winter, so i guess they are all considered wild anyway these unusual one are much taller with serrated heart shape leaves. They definitely are folloing the sun across the sky where the others are pointed in the direction in which they bloomed. I think folks get in a habit of generalizing and like pat answers, where it could more fun to be an oberver and to see the many variations in nature. I love sunflowers. peace ~