[CANUFNET] Elms and breakage

[Michael Richardson via CANUFNET]

Without seeing them I have no idea what you are seeing.  Are you seeing
breakage of limbs or unions?  Clusters of limbs breaking out? What are the
unions you are seeing?  Y vs. U?  With branch bark ride or without?  With
or without cracks?  Cracks on one side or two?  With bark inclusions or
without?  With cup unions or without?  With "ears"or without?   What
combination of these?

My gut says that 15 cm DBH elms that have never been pruned have been
"topped" in the nursery at 7.5 foot to encourage a "head" which results in
multiple branches arising from adventitious and epicormic buds within a
very short vertical and circumference area.  This results in a very poor
structure that is destined for failure as limbs have reduced safety
factors as the cross-sectional area holing them is far less than the
cross-sectional area of the limb above the union..

Michael


> All:
>
> At a conference in Quebec City I learned that much of the areas around the
> parliament buildings were being planted with Accolade Elm with good
> success.  After that conference we started incorporating elms into our
> street tree planting plans.  Accolade wasn't always available so there
> were often substitutions (Valley Forge, Princeton, Pioneer, Triumph.)
>
> I have recently noticed that some of the elms (when reaching about 15.0 cm
> dbh) are starting to break apart and large branches are failing.  Many of
> these elms are vigorous growers and municipalities haven't been able to
> keep up with pruning to keep the form strong.
>
> Has anyone else noticed this predisposition to breakage?
>
> Thanks.
> Alison
>
> Alison Bond BSc MSc BLA   OALA  CSLA
> Landscape Architect and Certified Arborist
>
> ENVISION-TATHAM Inc.
> 115 Sandford Fleming Drive, Suite 200, Collingwood, L9Y 5A6
> abond at envision-tatham.com I  Tel: 705.445.0422  I  Fax: 705.444.2327  I
> Cell: 705.994.2059 I   www.envision-tatham.com
>
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