Sunflowers Not Facing The Sun?

[daz1969]

We have always grown sunflowers

[ducksie]

Have you planted them elsewhere in the garden this year, young flowerheads face the sun but once they mature they face east permanently

[ducksie]

Better explanation found on the web

Well, actually it's both. First, not all sunflowers are phototropic. It's usually the sunflowers with a single-head (the ones with many heads facing in all directions their heads don't move with the sun).

The phototropic ones only follow the sun for a period. When the sunflower is growing the stem & material is soft and pliable, the unbloomed bud is light and will follow the sun during this phase. However, when the sunflower blooms the sunflower slowly stops growing, instead putting the energy into the seed head. At this point the rest of the sunflower (stem, etc.) starts to solidify, and will eventually solidify facing in an eastwardly direction and the bloom will no longer follow the sun. So, the phototropic ones do follow the sun but only for a time and once bloomed will eventually "freeze" facing in an eastwardly direction.

My guess is, they solidify as a mechanism to help support the head which gets bigger and heavier once bloomed. If they didn't solidify they would eventually collapse under the weight of the seed head as it matures.

[DTCwordfan]

Don't they turn into moonflowers then?

[Chipchopper]

I've been watching my sunflower heads following the sun, as it moves across the the sky from east to west but as the plants matured, they stopped about 1/2 way and hung down (job done).
I now have lots of seed to feed the birds, plus plenty of seeds to grow for next years crop.
Someone gave me the packet of seed, so it didn't cost me a penny!

[daz1969]

Thank you all for your excellent answers - I really appreciate it