Yellow and blotched leaves on sunflowers

I have a couple of potted sunflowers with leaf problems. The lower leaves are turning yellow and dying on one massive sunflower and on one of the chianti sunflowers the leaves are blotched. I put them up at:
http://www.brandylion.com/images/sunflowers
I have other potted Chianti and massive sunflowers with no problems like this and getting similar amounts of light. Is it a soil problem or water? All sunflowers were planted in 16" high 12" x 12" containers.
!
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Mine do the same thing every year, I just remove the leaves, and mine are planted in the ground. Looks like you have an interesting container garden going there, have you grown sunflowers before in pots? Very nice!
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Ann, Gardening in zone 6a
Just south of Boston, MA
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In article snipped-for-privacy@thecia.net says...

Last year I grew Chianti sunflowers and they turned out nice. This is my first time growing the massive sunflowers which can grow 10' high. I put them in 16" and 18" deep pots thinking that these sunflowers would grow deep roots to support itself. Which brings up a different issue I have. I really wish those plant tags that accompany seedlings you buy from the store would also include root depth and width. They say how high the plant gets and how wide but in container gardening it would be useful to know how deep of a pot that plant has to be planted in.
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No, they're roots aren't really deep, they're wide. I guess they just expect you to know, or to look it up somewhere.
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Ann, Gardening in zone 6a
Just south of Boston, MA
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Ann wrote:

Last year I started a lot of sunflowers early in small pots (about 2 inches). I had a lot of "extras" and I give them to a neighbor and she transplanted them into eight inch pots. I planted all mine in the ground and the ones that she had in pots did just as well as the ones I planted in the ground. Her only problem was that they needed to be watered a lot (sometimes twice a day) and they got top heavy and blew over a few times. By the way, these were not the real tall yellow sunflowers, they were a verity that grew about five feet tall (and had seven inch blooms). Here is a picture of one of her sunflowers from last summer: http://members.iglou.com/brosen/cgarden4.htm (bottom row, center picture).
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Bill R. (Ohio Valley, U.S.A)

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