Oops, not that kind of deadhead! Garden tip for the day: For many flowers that grow with heads like cosmos and roses, if you cut off the flowers that have died (deadheads) many more blooms will come. The most obvious reason is that when you cut of the dead part the plant does not have to send energy to support it and it can send more energy to growing new blooms.
Also on this note, let's say you have transplanted seedlings you sprouted in a greenhouse or inside your house, sometimes if you leave them in the flat they start flowering too early or when they're too small, think a 6 inch sunflower. They reach capacity in their tiny cell and the roots run out of room. The plant thinks it's going to die soon (perhaps it might) so it starts to produce the flowers, ie. the part that spreads its seed. So if you can get that sucker into the ground so it has room to grow AND you cut off the flower head it puts more energy into growing big and strong and very likely it will produce normal size flowers at the right time.
One more fun fact. If you happen to wake up early and take a walk through a garden, like the one here at Green Gulch and you walk down the path admiring the lavender you might notice what looks like many many dead bumble bees all over the blooms. Do not despair! These wonderous furry little creatures are just sleeping. I guess they are not like honey bees that usually go back to the hive to rest these party animals just pass out after a days work and wake up when they feel like it and get right back to it. Good times out here, good times.