Not sure of the type of sunflower I have but the heads are bowing down. Do I stop watering them? What is their life span once they've bloomed? And once they are cut off and dry do I pull the seeds off for the birds or leave them on the head? Thanks.
Larimer County Colorado sunflowers
Generally the sheer weight of the sunflower head causes it to droop or "nod." Sunflowers tend to be fairly drought resistant..consider the wild ones growing along roadsides. So they probably don't need a lot of irrigation each week, unless you're growing them for cut flower production. Birds will find the seeds without having you remove the seeds.
Here's a great link to sunflower information from the University of Minnesota: http://www.extension.umn.edu/yardandgarden/ygbriefs/h118sunflowers.html