North American Fruit Explorers mailing list at ibiblio

[Sarah Kehler Ewing <skkewing@yahoo.com>]

Hi Matt,

Yes it is.  In northern regions the sun is so low on the horizon all winter 
that it strikes the trees almost perpendicularly to their trunks.  The result 
is that the tree bark warms up and the sap gets flowing while the sun is on 
it and then the sap freezes when the sun goes down splitting the bark open.  
A few repeats of this and your tree is very damaged.  Local Birch trees have 
been known to have 1" wide cracks that flow freely with sap in the spring, 
but for some reason it doesn't seem to bother them as much as it bothers the 
fruit trees.

I read in a very old fruit tree book that an alternative to painting tree 
trunks used to be merely planting the tree with a 23 degree tilt towards the 
sun thus preventing the perpendicular sun strike!


Sarah 
zone 3
Edmonton, AB


--- On Tue, 3/31/09, Matthew Oller <matthewoller@yahoo.com> wrote:

> Helene, I thought it was , also to
> reduce cracking, from extreme temperature changes,and
> primarily on the south sides of trees,no?, matt,peace
>