North American Fruit Explorers mailing list at ibiblio

[Hélène Dessureault <interverbis@videotron.ca>]

Hi Derry,

I am not sure why you mention interstem. Is it to reduce size or for 
incompatibility between some varieties?

In cold climates, such as zone 3, it is not really necessary to interstem 
tree to reduce the size, as trees grow more slowly in colder climates, due 
to the shorter growing season.  For instance M111 (semi standard size) will 
usually grow like a semi dwarf. I feel that it is such a treat to have trees 
producing fruits in colder climates, that the size of the tree is not a big 
issue.

In my zone 3 to 4 (opinions varie on our exact designation) the main 
obstacle is the cold. A tree that will make it for many good years may 
suddenly die or die back under extreme winter cold-thaw situations which are 
the worst for killing trees. In such conditions, P. ussuriensis survives 
with complete indifference to the climate it seems. The problem with P. 
ussuriensis is that it is said to have incompatibility with some pear 
varieties for grafting.

With P. ussuriensis, I have done top working. My 15 trees had very little 
growth at first. After a while, they seemed to catch up as if the tree has 
to establish a good root system before developing upward growth. Top working 
is interesting because you get many branches of a variety to produce a 
decent crop while your main tree structure remains the rootstock which in 
the case of P. ussuriensis is cold hardy and sturdy too. You can do a few 
branches first, and continue top working using extra growth on the grafted 
branches as additional scion wood. You can also do more than one variety, if 
you so desire. You can also push your luck with varieties that would not 
normally grow in your area. The point is that there is less consequences 
when one branch breaks or dies, than when the whole tree breaks or dies 
after many years.

Incompatibility can be a problem though and I am not sure how it works. What 
I have seen is a good growing pear tree on P. ussuriensis literally 
separating at the graft union under a strong wind and the tree falling over. 
On close observation, you can see that callusing has partially formed 
between the grafted wood and P. ussuriensis inside so that the union joint 
is not perfect (not as good as it should be). Other grafts I have seen, on 
apple trees for instance, often have joint that is so perfect that after a 
few years, it is difficult to find the grafting point. Not so with P. 
ussuriensis. We call this incompatibility, but maybe it is simply due to the 
way P. ussuriensis calluses its wound... I would be interested to hear other 
opinions on this subject....

Claude, yes the one and only, sent me a nice selection of pear scion wood 
last year. The favorable weather (Warm temperature and lots of rain which 
stimulated cambium flow) and some years of grafting practice combined to 
produce near 100% takes. Each variety was grafted unto two P. ussuriensis 
with at least two takes on each tree.

I am hoping that topworking on P. ussuriensis will ensure a stronger long 
lasting tree.

Hélène, north of Ottawa zone3-4


----- Original Message ----- 
From: "derry&bill" <wchase@interchange.ubc.ca>
To: "North American Fruit Explorers" <nafex@lists.ibiblio.org>
Sent: Sunday, January 18, 2009 1:29 PM
Subject: Re: [NAFEX] Grafting pears


> Claude,
>
> The one difference I can think of with grafting pears is the necessity
> of an interstem with most pear varieties if you are using quince r/s.
>
> But maybe you are all using the OHF r/s?
>
> Derry Walsh
> South Coastal B.C.
>
>
> Claude Jolicoeur wrote:
> > Ginda,
> > Pear grafting is exactly the same as apple...
> > Claude
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