North American Fruit Explorers mailing list at ibiblio

[Alan Haigh <alandhaigh@gmail.com>]

>Might the problem be specific to Northeast conditions? Humidity or fall
rains? Soil ph or microbiome affecting hardiness? Changes in >autumn
conditions that might affect a tree's ability to achieve full dormancy?

Because hardening off is a process that includes the reduction of water in
the cells, anything that might change a trees ability to do this might
contribute to the problem in the northeast, however it would take a great
deal of research, I think, to sort it out.  I've never kept serious records
on the issue to methodically compare weather conditions on years when
mortality is high to when it is not.  I don't manage enough apricot trees
to justify going to this effort (the data would be relatively
insignificant) and it is not an important enough commercial crop here to
probably spur funding for such research.

However, Rutgers considers the species valuable enough to devote quite a
bit of expense to breeding better, hardier varieties.  I haven't heard of
them doing any research on the specifics of what causes them to be
relatively tender in the East.

My guess is that it does relate to the relative humidity of our climate as
that seems to be the only significant difference from the conditions
experienced by the high desert trees of the interior West.  There is a wide
range of pH in the soils of sites I manage but I use amendments to keep
them between 6.5-7.5.