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In the Lower Mainland of BC a few of us initiated spiral pruning as
a technique to reduce the likelihood of windthrow, in the early
90's. Initially it was mainly Douglas-firs, hemlocks, and redcedars
along new edges as development occurred. Later it was tried on
isolated trees. <br>
<br>
As an edge treatment for newly exposed trees in a forest it works
well. It opens up the edge to be more 'porous' and the wind
dissipates back into the forest stand without triggering windthrow.
As a treatment for individual trees trees it is less successful, and
on Douglas-fir, very harmful. When we started it over two decades
back, we had heard a little about branch clashing, wind sail etc and
it seemed a logical approach. It turns out that, at least in
Douglas-fir, the branches need to clash. When they were removed as
part of spiral pruning they moved a lot more in strong winds and
increased branch failure resulted, which in turn allowed other
branches to move more and encouraged additional branch failure. I
recall seeing isolated Douglas-firs that had been spiral pruned,
looking very motheaten years later, with massive amounts of limbs
broken off. The trees not touched seemed just fine and few had
fallen down.<br>
<br>
These days I would not prescribe spiral pruning for an individual
tree that is isolated. I would still recommend it as part of edge
treatment for newly exposed trees (any species) in forest
conditions. It should not be prohibited in all circumstances. Like
many treatments there is a time and place where it can be very
effective as means of meeting defined management goals. <br>
<pre class="moz-signature" cols="72">On Behalf of Dunster and Associates Environmental Consultants Ltd.
Dr. Julian A Dunster R.P.F., R.P.P.., M.C.I.P., ISA Certified Arborist,
ASCA Registered Consulting Arborist # 378,
ISA Tree Risk Assessment Qualified
BC Wildlife Danger Tree Assessor
Honourary Life Member ISA + PNWISA
<a class="moz-txt-link-abbreviated" href="http://www.dunster.ca">www.dunster.ca</a>
Distributor for Air Spade. <a class="moz-txt-link-abbreviated" href="http://www.air-spade.com">www.air-spade.com</a>
North American Distributor for Rinntech equipment. <a class="moz-txt-link-abbreviated" href="http://www.rinntech.com">www.rinntech.com</a>
</pre>
<div class="moz-cite-prefix">On 11/05/2015 8:47 AM, Hamilton, Emily
wrote:<br>
</div>
<blockquote
cite="mid:0939E813E4AAC44CB0D1E9C25193D5A7992594@exchpdc3.surrey.ca"
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<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#222222;background:white;mso-fareast-language:EN-CA">Good
morning,</span><span
style="font-size:12.0pt;font-family:"Times New
Roman","serif";mso-fareast-language:EN-CA"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#222222;mso-fareast-language:EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#222222;mso-fareast-language:EN-CA">We
are looking into justification for or against spiral pruning
here at the City of Surrey and I was wondering if anyone had
any experience or documentation that they'd like to share
related to this. Any thoughts? <o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#222222;mso-fareast-language:EN-CA"><br>
Thank you,<br>
Emily<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
style="mso-fareast-language:EN-CA">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
style="mso-fareast-language:EN-CA">Emily<o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
style="font-size:9.0pt;color:#404040;mso-fareast-language:EN-CA">Emily
Hamilton | Environmental Technician - Arboriculture<br>
<br>
<img id="Picture_x0020_1"
src="cid:part1.07020201.04010102@gmail.com"
alt="COS_Tag_pp_cmyk-200" height="73" width="200"><o:p></o:p></span></p>
<p class="MsoNormal"><b><span
style="font-size:6.0pt;color:#76923C;mso-fareast-language:EN-CA"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:9.0pt;color:#76923C;mso-fareast-language:EN-CA">CITY
OF SURREY<o:p></o:p></span></b></p>
<p class="MsoNormal"><span
style="font-size:9.0pt;color:#999999;mso-fareast-language:EN-CA">Trees
and Landscape Section, Building Division – Planning and
Development<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:9.0pt;color:#999999;mso-fareast-language:EN-CA">13450
104th Ave, Surrey, BC, Canada V3T 1V8<br>
T 604.591.4560 </span><span
style="color:#1F497D;mso-fareast-language:EN-CA"><a
moz-do-not-send="true" href="http://www.surrey.ca/"><span
style="font-size:9.0pt;color:#76923C">www.surrey.ca/treeprotection</span></a></span><span
style="font-size:9.0pt;color:#76923C;mso-fareast-language:EN-CA">
<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span
style="font-size:9.0pt;color:#76923C;mso-fareast-language:EN-CA">Connect,
Share and Engage with your City<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-CA"><o:p> </o:p></span></p>
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