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@dal.ca>
To:
<
nafex@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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