>
> > A flash of hot weather can even mess up the sequence of bloom
> dates...squishing them all together rather than the normal one after
> another


We certainly see this in almonds, in which 3-4 varieties with different
blooming "dates" are planted in the same orchard.  In some years, all
varieties bloom separately, over  a period of a month; in other years, all
bloom at the same time--sometimes all stating on the same day!

This spring, as I drove repeatedly from the Calif foothills down to the Bay
Area (a 3000 ft drop in elevation) I noticed something that hadn't come to
my attention previously.  Driving down in elevation is like going forward in
a time machine as far as plant phenology is concerned--you drive forward in
spring with each foot drop in elevation.

However, what struck me was that one shrub--California Buckeye--initiated
bloom at about the same time at all elevations, despite the fact that other
flowering plants on my route followed the normal progression of bloom of
about a month difference from top to bottom.

The Buckeye appeared to be more regulated by photoperiod than by
temperature.
-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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