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[nafex] Hardiness/topworking observations

Since its -30C with ice fog developing as I write, with only about 1/2 inch
of crusted snow/ice on the ground, hardiness (hopefully) of my test orchard
does come to mind...So I thought I'd answer a couple of questions from my
topworking experiments over the last 10 to 15 years from my experience.

Bark grafts of apple above the snow don't increase the hardiness at all, and
probably might even decrease it.  An example would be, say, a 3 inch stub
with a bark graft growing from one corner.  My guess is in cold weather the
graft union gets too cold due to dead wood in the stub, and the grafted part
seems to die.  If you are grafting to increase hardiness, don't do it this way.

By far the best results are whip and tongue horizontal grafts joining equal
sized branches/scions.  In a couple of years its hard to see the graft
union, and situations like this are where most of the best hardiness
increases occur.  A verticle whip and tongue graft of equal sized
branches/scions still adds hardiness, but not as much as the horizontal
ones.  My guess is the verticle grafts grow too much and tend to harden off
a bit later which makes them a bit less hardy.  Bottom line - if you are
grafting a tender apple that won't normally survive in your climate and want
to give it the best possible chance to survive and produce, use a basically
horizontal whip and tongue graft with the scion and branch being nearly the
same caliper.

Should you leave a branch of the frame tree on to increase hardiness?  The
jury is out on that one. I've noticed an interesting phenomena.  A McIntosh
branch on a September Ruby tree in Edmonton in late September is still
green, and almost looks like it thinks its still July.  The frame tree
however, has lost all its leaves and is gritting its teeth, preparing for
another prairie winter.  So the grafted-on variety doesn't appear to lose
its leaves any earlier if you leave branches of the frame tree on.  So it
may well not be necessary to have a branch of the hardy variety remain on
the frame tree.  I've done it both ways, with about equal hardiness results.
I suppose superstition, if nothing else, would lead me to leave a branch or
two of the frame tree on.

Re topworking plums - All topworking of various hardy prairie plums
(Pembina, Brook Red, etc) on Americana seem fully hardy for me, but as I
mentioned not the European ones I've tried (Stanley, Mount Royal, Italian
Prune Plum, Greengage, etc).  This may be a combatibility thing.  As an
example, Mount Royal grafted on Americana at ground level makes a very
dwarfy, 3 ft. bush with poor production from what I've seen, but it does
seem to survive.  Grafts above the snow of european plums on americana
always seem to die in my climate. 

Lastly Evans cherry grafts - I've grafte Evans on everything I could find,
Nanking cherry, double flowering plum, several different hardy plums, etc.
All die in the first winter.  I have heard of very limited survival for 2 to
4 years on native wild pin cherry, but its just not worth it in my opinion.
Just grow it on its own roots and its plenty hardy in zone 3.
Bernie Nikolai
zone 3/2

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