[Arid_gardener] RE: pruning Palo Verde trees

[Donald Garnett]

Hello everyone
 
Can we have some discussion from the experts on the question of pruning
Palo Verdes? I know that pruning of many trees is best done in the winter,
but there is a great deal of conflicting opinion on Palo Verdes. Tyler has 
pointed out important reasons for not pruning in summer. However, Eric
Johnson's guide indicates that June is the proper time for pruning the various
Cercidium species. In his defense, he does recommend against *heavy* 
pruning, "as large cuts seldom heal well". So perhaps Veronica's problem are
not due to the timing of the pruning, but the fact that it was "severe" as
she characterizes it. 
 
The conflicting opinions are confusing to we who are trying to prune our 
trees/shrubs correctly. Palo Verdes certainly present a challenge as they
have different characteristics from typical trees, but it would be helpful 
if we had a better idea of what, if any, research brings to bear on the 
subject.
 
     Don Garnett
     Tucson, AZ> ------------------------------> > Message: 2> Date: Wed, 12 Sep 2007 10:21:41 -0700> From: "Tyler Storey" <tyler at tylerstorey.com>> Subject: RE: [Arid_gardener] Palo Verdes> To: <veronicaavarela at cox.net>, <arid_gardener at Ag.arizona.edu>> Message-ID: <000a01c7f561$64645bc0$0b00a8c0 at TVS>> Content-Type: text/plain; charset="us-ascii"> > Good morning Veronica,> You have witnessed one of the great truths of caring for trees: pruning> doesn't make trees smaller, it makes them bigger. > > What you describe sounds like the very common response that a Palo Verde> tree will have to being pruned: the formation of dead-looking brown "scar"> tissue around the cuts that ends up covering the branches and trunk. Some> of it may also be a response to increased sun levels hitting the bark as a> result of the pruning, burning and killing the bark and resulting in the> same formation of brown tissue. > > A couple of things about pruning trees. First, you say it was pruned a> couple of months ago, June or July, and unfortunately that may be the worst> time of year to prune a tree. You'll have noticed that a Palo Verde has> very thin bark, really more like skin than what we think of as bark. What> we tend to think of as bark, the rough brown scaly stuff we might see on an> oak, or pecan, ash, pistache, or pine, is made up of "dead" material, a> corky layer that forms the outside surface of the trunk or limbs. That kind> of bark provides a protective surface for the tree, shading it from heat and> sun and the other elements. A Palo Verde doesn't have that protective layer> for the most part, though it can develop with age. > > When a Palo Verde is pruned in the sun-intense Summer months, that delicate> green skin is suddenly exposed to elevated levels of direct Sun. It becomes> damaged and responds by either dying or by producing the "scar tissue"> you're seeing now as a protective layer. Additionally, you've probably> noticed that a lot of the brown stuff is around where it was cut during> pruning. Same thing: the tree's response to fixing the injury it sustained> during pruning. > > The damage you see was caused by the pruning, through sun and die-back.> There is unfortunately no way to treat it. > > Now you also mentioned the trees are again in need of pruning. You might> pause to reconsider. Pruning, as you noticed, stimulates new growth. New> growth makes the tree larger. Larger trees may need more pruning. You may> be embarking on a never-ending cycle that is going to result in these> beautiful trees that enhance your landscape becoming a high-maintenance> pain-in-the-neck covered with scaly brown stuff from top to bottom. > > Always stop to ask yourself "why?" before you prune. A large tree is> generally a good thing. They cast shade and help keep us cool, reduse our> cooling bills, and provide a pleasant "ceiling" for our landscape. Unless> they are impinging on a power line, consider leaving the large trees alone.> Trees do not, for their own health, ever need pruned if they are properly> cared for. Prune only to remove dead, damaged, or diseased limbs, and never> prune at the height of Summer. You might prune slowly, over time, if you> need to "lift" the canopy to walk under it, but that's really about it.> You've seen the results of severe pruning, and unfortunately that damage s> permanent, but you can avoid similar damage in the future. > > I hope this helps,> Tyler> > tyler at tylerstorey.com> http://tylerstorey.com> 602-738-2978> > -----Original Message-----> From: veronicaavarela at cox.net> Sent: Wednesday, September 12, 2007 6:05 AM> To: arid_gardener at Ag.arizona.edu> Subject: [Arid_gardener] Question from Home-Hort WWW page> > veronica> 85226> veronicaavarela at cox.net> > We live in Chandler and about two months ago had 2 well established palo> verde trees pruned as they were huge. The pruning was severe but the trees> bounced back and actually are once again in need of trimming . Problem...we> have noticed striations on trunk and brances...splits and holes that are> highly visible as they look like dry,brown streaks, patches and holes. They> increase daily and now cover most of the trunk as well as major branches.> What is it and can it be treated? These trees are very beautiful and really> enhance our front landscaping....
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