A year has passed and another leek flower has opened for me.
Apparently, what causes leeks to bolt is a sudden heat wave.
I consider leek flowers a delicacy and would grow them all year round if I knew how.
Because I don't have much viable garden and space for outdoors, and normally do not stay in one place long enough to see through a normal growing season, I buy leeks at the produce store and stick them in glasses of water on the window sill or next to my AeroGarden planters. This one had been neglected and grew a curvy stem about a yard long before I noticed the bud, which was what saved it from becoming leek soup.