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[Waite8@aol.com]

In a message dated 2/15/03 6:49:35 AM, jbunker@gwi.net writes:

<< on 2/14/03 5:56 PM, Waite8@aol.com at Waite8@aol.com wrote:

It is VERY cold in Maine this weekend with temps dipping way below zero. Is
there any guideline on what temps. are too cold to do pruning? Would like to
get some in this weekend. Maybe some of the Mainers can tell me what they
are doing. Thanks. Waite Maclin, Cushing, ME.


Greetings Waite,

Friday morning it was -30 here and this morning it is -28. I've been in
Palermo 31 years and I think these are the coldest two nights in row I've
seen.  Large commercial orchards in Maine generally begin pruning in early
winter because they have no other choice.  Most winters I begin pruning
about now.  This winter I will wait another 2 weeks or so.  I've never seen
it much below zero after March 1st.   I would recommend you wait until the
weather warms up.  Some years I prune well into April with no adverse
effects.

Cheers >>


Thanks John. I did some of the trees last weekend and a few today before I 
got your e-mail. I am going to wait till mid-March. I was anxious to get 
started as I will be out of the country till then. Hope to see you soon. 
Peace. Waite
>From bnikolai@shaw.ca  Sat Feb 15 17:13:01 2003
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Date: Sat, 15 Feb 2003 15:10:49 -0700 (MST)
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From: Bernie Nikolai <bnikolai@shaw.ca>
Subject: Re: [NAFEX] Re: Cold weather pruning Advice
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Del wrote:

 What is the mechanism that allows a whole stick 
>of dormant wood to dry out through a small end cut? I thought the juices 
>quit running in the winter.......Del

Hi Del,
        I'm no scientist, but I have thought long and hard about apple tree
hardiness (of necessity) in my climate.  The dormant scionwood stick won't
dry out, as I assume you have it in the fridge in a plastic bag with damp
paper in the bag.  But I think you mean "why would the tree you took the
scion from dry out and be injured?"
        Here's my theory, but keep in mind I have never seen any scientific
studies to support my beliefs.  In cold climates like ours, a fruit tree
survives by ridding itself of as much moisture as it can in the cells.  Ice
crystals, which are very jagged, will rupture the cell walls, killing the
tree if they don't.  Apple tree hardiness really means the trees that can
desiccate or dry themselves out the most, then rehydrate when it warms up,
are considered the most hardy.  Tender trees either don't desiccate enough,
and the ice crystals in the cells rutures the cell, and kills the tree, or
else they do desiccate enough, but can't rehydrate succussfully, so they die.
        Take a good look at your trees on any cold day, well below 0F.  You
will see the thumb thick brances are all shrivelled up, with wrinkled bark,
similar to taking a long bath and seeing your skin on your hands all
shrivelled up.  When the temperatures get back to near freezing, whether
that is in a day or in a month, take another look at the same branches.
They are fully rehydrated and look totally normal again!  I am not
hallucinating on this one Del, check it out for yourself, its an amazing
phenomenon!  That's why the LENGTH of the cold spell is often more important
than the actual minimum temperatures in our cold zones.  A week of -40 (F or
C) is way tougher on the trees than one night of -40.
        Now as to how the tree "rehydrates", there are only three possible
ways, 1/through the roots even though the ground is frozen solid, 2/ by
sucking in moisture from the outside air, or 3/ by a combination of both.
It is possible only a very small amount of moisture from the roots is
needed, at least compared to summer conditions with lots of leaves and
evaporation.  So possibly the roots do send a very small amount of moisture
back up to the branches despite being frozen.  Or possibly the tree can just
suck the moisture straight out of the air.  After all, that's why we store
dormant scions in a humid environment by adding damp paper.  If the scions
are stored at the right temperature, but bone dry, they often die in storage
after a while.  So obviously they have the ability to some degree to pick up
moisture from the atmosphere.  And also it doesn't have to be a lot of
moisture, but it appears to be a very delicate balance, and some small
amount of moisture is essential.
        Pruning in cold weather upsets this delicate balance somehow, and I
believe its because the tree looses moisture that it can't replace in
winter.  I've noticed the same phenomenon one year with "scoot", a waxy
coating with thiram to deter mice and voles.  I really coated a few small
trees, way thicker than normal, so they had a "coat of wax" on them.  I had
SEVERE winter damage on those trees, even though they were very hardy!  I
believe this was due to the tree being disrupted in terms of getting out or
getting in moisture during the winter months.  The wax didn't allow normal
transpiration.
        So Del, most of the good folks on this list live in the virtual
"tropics" compared to our winters, and can get away with all kinds of things
such as mid winter pruning that we can't begin to get away with.  But it
makes growing an orchard in our climates all the more challenging and fun!
We all have different challenges no matter where we grow.  My advantage is
all my trees are fully organic and never sprayed.  There is no such thing as
a codling moth, apple maggot, borer, plum circulio, or apple scab at my
orchard, and the fruit is perfect or very near perfect without any sprays.
I suspect very few on this list can grow high quality pome fruit in the same
way without any pest control of any kind.
Bernie Nikolai
Edmonton, Alberta