Sunflower question

[Erica]

Hi all,
I hope this is the right forum. Anyway, this is an odd question but do sunflowers adapt to the space they are planted in or what? I got the seeds out of my bird seed bag "Black sunflower seeds". I just planted them to see if they would grow... and they did... but not all the same!
I planted seeds in three spots in my yard. The ones in my veggie garden are 16 feet high and HUGE, the ones in my smaller flower garden are only about 8 feet high and have smaller flowers on it and the ones I planted in a flower box are only 4 inches high and look like mini sunflowers.
What's that all about?
Erica ;0

[Carol Ja]

Assuming that they were actually all the same variety, they would be different for various reasons, soil conditions, amount of light, amount of water.

[Daniel Mosquin]

Aha, a scientist!

What you are observing is the physical response to growing conditions, even though the seeds (likely) share a similar genetic background. In scientific terms, it would be said that these sunflowers exhibit a high degree of phenotypic plasticity, or variability in physical form due to outside factors (including at least some, if not all, as suggested by Carol).

See genotype-phenotype distinction on Wikipedia.

[Erica]

Thanks guys..... soooooo.... if I plant other so-called large flowers in a flowerbox would I get little versions? for example, would a gladiola bulb bloom smaller if it was in a small pot? Maybe I will try next year.
Thanks for the replies.

[Daniel Mosquin]

Not all plants have a high degree of phenotypic plasticity , but it sounds like a fun experiment.

[jamkh]

Erica, what an interesting observation,
I believe the different sizes is more dictated by the amount of nutrients available to the plants, assuming your soil structure and watering frequency remains identical. Of course with any batch of seeds from one mother plant, you are bound to get about 3 to 5% of the seedlings who turn out to be dwarfs. But this genetic feature is not what made your potted sunflowers small. The potted ones are akin to bonsai due to their restricted root growth.
Erica, did you observe how the sunflower turns its head to follow the path of the sun get maximun light and that the sunflower seed bracks carry out photosynthesis as well? Interesting behavior.

[Erica]

Hey, yes, I did observe the larger sunflowers turning their heads but the smaller ones didn't. Guess they didn't have the strength. Thanks for commenting.

[jamkh]

Erica,
Since I mentioned seed bracks, Please conduct this simple experiment next time you grow sunflowers. As the flowers open, pluck all the bracks from the left side of the flower head. You will find that the right side produces viable, healthy seeds but the left produces only seed coats, devoid of embryos. No food, therefore no good seeds. Interesting!

[Erica]

Hey, I'm pretty unknowledgable about sunflower seeds but I thought if I dried the whole head at the end of the season that I would get a full supply of healthy seeds. Is that not true?Do i want to pluck some so that the others are viable?
Thanks

[jamkh]

Erica
No. that wasn't my intention. I was just pointing out the fact that these seed bracks do make food for the sunflower. In fact I was totally surprized when I got a whole flowerhead of empty seeds on it. And the sunflower has such giant leaves as well, you would think they make sufficient food for the seeds. But remember the flower head can be enormous, measuring 2 to 3 feet across with tons of seeds.

[Erica]

Ok, gotcha, Thanks

[haul0348]

Also the depth of the soil can help or hender the plant growth the more room the roots have to grow will aide in the overall growth.