"........in winter the sun side heats up because the bark is dark, the
shaded side doesn't heat up, the differential in heating results in
differential expansion which leads to cracking of the bark. I would rather
whitewash than wrap the trunks. Ingrid........."

Interesting

Top fruit planted against walls (Espalier and cordons) was a very important
part of Victorian gardening in the UK, and I have never come across any
reference advocating painting the trunks.
Could be that we don't have the same strength of sunshine here in the UK.

Also some of the walls were actually heated with a series of cavities
running through them and the heat from fires being drawn through them to
give extra warmth to both protect the trees and to give them an earlier
start.
One idea being that the fruit on the South facing wall was first followed by
the fruit on the West wall then the East wall thus giving a succession of
fresh fruit.
Remember that these were the people who by the early 1800's were growing and
fruiting Pineapples under glass in the UK.

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk