How do they know?

I made a hearty bouquet last week of wild tiger daylilies and spiderwort (Tradescantia ohiensis that I placed in a cobalt blue vase to greet me in the morning and accompany nighttime meals.  This lively contrast of oranges and purples contained flowers in bloom and those in waiting.

On day 2, several of the lilies had closed and dried while others had bloomed.

On day 3, several other lilies closed and dried.  New ones bloomed.  The same held true for the spiderwort pods.

As this process continued throughout the week, I noticed that each bud seemed to be taking turns in its cycle of life.  I wondered, “How do they know when to bloom and when to die?”