Yellow leaves before reblooming
 

I have about 25 orchids. They are dong well and produce flower spikes regularly. Sometimes more than one spike.
A friend of mine said that she was waiting for her orchid (she has only one) to produce a spike and bloom but one of the bottom leaves had not turned yellow yet. She said that the orchid - a phalaenopsis-didn't bloom until a bottom leaf tuned yellow.
I was surprised because that does not appear to occur with my orchids. Some bottom leaves do turn yellow and fall off but that does not seem to coincide with the production of a flower spike. I seem to get spikes when my orchids start to put out new leaves.
Is there any relationship between the production of the flower spike and a bottom leaf turning yellow?
Thank you in advance.
Elaine

Sounds like your friend may not be fertilizing regularly, causing their phal. to scavenge mobile nutrients from the oldest leaf in order to flower.

Usually, my Phals shed their oldest leaves right before a new leaf starts to grow. I think this is part of their growing cycle. More or less at the same time, or most frequently, right before that stage begins, that's when they spike. In this cycle of spike-shed leaves-new growth, the blooms are the last to die.
I don't think it has something to do with anything else than their normal living cycle.