[NAFEX] Spring grafting

Dr.O'Barr Topgun at Otelco.net
Wed Apr 7 21:03:38 EDT 2010


Dasvid:
I am sure others will have a lot more to add (or subtract), but for what its 
worth, I have grafted scions that had small leaves coming from each bud on 
pear and using parafilm had good take. Could it be that the terminal bud is 
a bloom bud while the proximal buds are vegetative. Bloom buds open ahead of 
vegetative from my experience.
The only problem I have experienced from a rootstock being active is from 
the excessive sap flow and subsequent souring, sometimes. Some grafters take 
elaborate means to drain off and excessive sap by extra cuts. Of course this 
is for bark grats not whips.
Good luck in 2010.
Topgun
Zone 7

----- Original Message ----- 
From: <david.maxwell at dal.ca>
To: <nafex at lists.ibiblio.org>
Sent: Wednesday, April 07, 2010 6:04 PM
Subject: [NAFEX] Spring grafting


>I have been field grafting my apple trees for 30 years (dormant scion 
>grafted to actively
> growing rootstock), but realised this year that I really have never 
> thought it through fully.  I
> have always taken "bud break" of the rootstock as the time to do my 
> grafting.  But this year
> we (and it appears, a lot of other places) have had a dramatically early 
> Spring, and weeks of
> temperatures in the high teens and low 20's Celsius - this translates to 
> 65-72 degrees F.
> This has caused buds to swell considerably, many now being at green tip. 
> But we are now
> predicted to have temperatures for the next week (or more), back down to 
> some 5 or 6
> degrees C (40 F), and I suspect that grafts placed now would never callus 
> in.  Any advice on
> when would be a good time to graft?
>
> And, a supplementary, (and far more problematic) question.  I have gotten 
> scion wood from
> several sources, who have been experiencing similar conditions.  This has 
> resulted in their
> cutting the scions after their trees had likewise started to break 
> dormancy.  Now the "gospel"
> is that the scion must be dormant to graft successfully.  But 1) I am not 
> sure I have ever seen
> any actual evidence of this - has anybody got any personal experience to 
> contribute?  and 2)
> more "scientifically", what is the mechanism here?  Is it a question of 
> changes in the cell
> walls of the cambium cells (which thicken in the Fall, as dormancy sets 
> in, and then start to
> multiply - with thin walls - as growth resumes) or is it rather a simple 
> question of metabolic
> demands in the scion which has started to grow (ie. broken dormancy), in 
> particular a
> question of water movement?  In the first instance, there is nothing we 
> can do to modify
> events.  But in the second instance, doing things to prevent the scion 
> from dessicating before
> it gets vascular channels established with the rootstock may be all we 
> need to do to get a
> good take despite the scion having broken dormancy.  Anybody got any 
> experience to offer?
>
> And, just to gild this lily a bit more, I note on one batch of scions, in 
> which the terminal buds
> were left in situ, that it is the terminal buds which have broken 
> dormancy, while the buds
> farther proximal on the stem are not obviously swollen.  If I use these 
> more proximal buds for
> grafting, am I likely to get a better take? (I suspect that what is 
> happening here is that the
> terminal bud is sending inhibitory chemicals back down, and keeping the 
> buds below from
> sprouting -  a non-temperature-related dormancy process.)
>
> And, finally, might I do better, with my non-dormant scions to chip bud 
> them, rather than graft
> (whip and tongue), on the principle that the metabolic demands would be 
> much less?
>
> David Maxwell, officially zone 5b Maritime Canadian.  (But more like 
> Florida at present)
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