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General view July 29, 2003 Our field has completed blooming and almost all the heads are drooping. You can still see some ray flowers. The plants still have good color and there aren't any noticeable drought symptoms.  We haven't had much rain since July 10th and we've had 8 days over 100 F.

R6 stage sunflowerThis R6 plant completed blooming several days ago. The bracts aren't as green as they were last week.  Let's look at the backside of the receptacle. 


R6 sunflower backsideThe receptacle and bracts aren't as green as they were.  This is normal development of the heads. They will eventually turn yellow. 


R6 sunflower cross sectionThe cross section of this head shows continued seed development.  Let's look a little closer. 
 


R6 sunflower cross section closeupThe seeds are getting larger.  There appear to be flowers in the center that weren't pollinated because there aren't many seeds there. These center flowers not developing seeds could be a symptom of drought stress.  We'll have to keep watching this to see if it's a widespread problem or if I just got a head that isn't that far along in its maturation.  


10 inch sunflower headWe haven't discussed this before, but there's an optimum head size that farmers like to see. The head on the left is about 6-8 inches wide, while the other head is about 10 inches wide. Farmers like to see heads about 6-8 inches wide because it allows for quicker dry-down of the head and seed. This will allow the farmer to harvest a field quicker. Harvesting a field sooner as opposed to later reduces seed or yield losses and as farmers get paid for the total pounds of seed, it is very important they harvest everything they produce.  But you're probably wondering how farmers make sure they end up with the right head size.  The answer is planting rates. Higher planting rates cause the heads to be smaller, conversely lower than optimum planting rates will result in larger head sizes.