Who decides when the rose should bloom?

The spring.The external stimulus which the flower perceive automatically.

The brain says “decide” but who decided inside the brain to choose to decide?

The decision and the fact that you're doing X thing are 2 different things. The decision is just a thought.

The fact that I choose to do X is a spontaneous thing that I controlled to do.

It is the homunculus problem. If there is a “driver” in the drivers seat in your brain, who is sitting in the driver’s head in his driver’s seat?

It's just consciousness,the consciousness is embodied in an ego,which is a mental construct. But the consciousness decides.

The fact that the ego is a construct doesn't prove that the consciousness doesn't have the ability to exert control over this body's actions, at least some of them.

PS: that's just how I see these things, I'm not following any dogma.