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Tree triage: Post-windstorm Q&A with arborist Rebecca Latta

December 7, 2011 | 10:55 am

Fallen tree in Pasadena
Ever since the windstorm blew through Southern California we've been fielding questions from readers: Can a fallen tree be replanted? When should I plant the replacement? What should I do if the tree is still standing but a major branch got ripped off? Perhaps most important, how should I prepare for the next round of high winds? For some information on tree triage, we turned to arborist Rebecca Latta for this edited Q&A:

Question: Is there any way to save a tree that has been uprooted by the wind?

It depends on how old the tree is and how much damage there is. If it's a young tree, with a fair amount of the root plate (the anchor roots) intact, then you can sometimes re-stake or re-guy (rewire) it. I have seen trees re-root. With older, larger trees, it's more difficult. To determine if the tree is a good candidate, you want to consult an arborist who is certified or registered. If there is an uprooted street tree in the frontyard and it looks like the root systems are in good shape — no big circling roots or crossing roots that may have caused it to fail in the first place — then it could be a good candidate. If severed roots can be cut cleanly and put back in, sometimes you can establish new roots to go back out into the soil. It's fairly involved. (The Pasadena tree pictured at top? Probably not a good candidate.)

Are there certain trees commonly seen here that are more susceptible to falling?

For street trees, I see a lot of pine, large pine, typically those that have a big sail, a fair amount of dense foliage. One of the common ways that trees are pruned here is that they are center stripped.  That means taking all the center foliage out, and that encourages the tree to become very dense in the center, making it more susceptible to failure. When the wind hits, rather than going through, it's like a wall. I saw a lot of cedars in Altadena that failed in the parkway because of root pruning probably done 20 or 30 years ago, when they were making curbing gutters or sidewalk improvements. I saw eucalyptus, mostly big branches dropping. Quite a few Chinese elm. Liquidambars.
 
Are there some trees that are surviving better than others?

That's a hard question. Wind damage is often a factor of the age of the tree, decay and how it's been pruned — or not. Some species don't seem to drop branches as easily. Oaks seem to be able to take wind, particularly if they haven't been center stripped. An oak with a full canopy that hasn't been pruned badly seems to do pretty well. Older oaks go over because people have been watering the ground around the tree, the lawn.  Lawns and oak trees are not a good combination. But I didn't see a lot of those types of
failures — this time.

Trees fallen

Brenden Mehaffey and his son, Collin, walk away from a crew clearing fallen trees on Eldora Road in Pasadena. Credit: Irfan  Khan / Los Angeles Times


What should you do with a tree that has a branch torn off?

You can cut it cleanly with a sharp, sterilized pruning tool back to another branch that is at least one-third of the size of the one you are taking off. Or you can take it back to the trunk if there is nothing else. If the broken branch is left hanging, it may fall off at some point. If the branch is not hanging but has a significant crack, that also can be a problem. I have seen quite a few trees where there is a crack up a trunk or a major branch. 

Can you put in guy wires or posts?

You can.  It depends on the tree. I have seen leaning trees with a post installed underneath; these trees have done well. I prefer to use posts over guy wires because I've seen guy wires done badly. They have to be adjusted yearly. I don't use cables or guy wires in trees very often. If the tree is leaning and it doesn't look like it's going to fall, you might put a post under it. The post has to be rated for the amount of weight and has to be designed with a sizable footing so it doesn't tip. Trees are heavy. If you have a smaller tree that is leaning and it is possible to right it, do that. If it's a bigger tree, leaning because of the wind, and it looks like it might reestablish itself in that position — and some trees do — that's when you might want to have an arborist come look at it.

Is the danger to trees structural? Or is it a matter of long-term health?

Both are true. It can be long-term structural. If you have a big crack you can't see because another tree hit it, that's an invisible point of weakness inside the tree.  Sometimes it will manifest itself in decay later on, a bump that comes out. Right now, the issue is structural.  Do other trees that haven't failed have the potential to fail?  Are there trees that can be restored with a pruning?  Or do they need to be removed? 

Is a tree safer if it has lost limbs in the center?

Not necessarily.  If the center has been blown out of the tree, then that means that you may have lower branches that are now big and heavy, so the tree might need a crown restructuring. 

What should I look for when I’m checking my trees? Are there things I should look for on the ground?

Look to see if there is cracking in the soil and if there is any pulling of roots or mounding on the side of the tree. If you see mounding and the tree is starting to lean, the tree could be moving. Cracks on the trunk of a tree that is leaning, especially if the crack is on the leaning side, are of great concern. That's bad. Sometimes a tree starts leaning after another tree falls. Sometimes when you change the environment, you will see things start to move. That's when you want to pay attention: When trees adjacent start snapping out because they have lost their support. You can also look for unusual things on the tree — bumps, sapping. If the tree puts out dark sap on the trunk, that's a sign it's stressed.

Is there anything that people can do now for their healthy trees to protect them from future wind?

Prune in the right season. Pine trees and cedars need to be pruned in the winter. Make sure you don't remove center foliage that is necessary for structural reasons. Concentrate on the outer two-thirds of the canopy. Don't let people center strip or top. Those cause wind failures. You have to make decisions about how to prune the tree so it doesn't drop more branches over time. If someone is going to come in and prune your tree, they should know why they are pruning your tree — not just reducing the height.  Trees need the ability to move in the wind. If you shorten a tree, you actually make it more of an immovable object. It is better to have the tree pruned properly and have evenly spaced branches and leave foliage in the center of the tree rather than topping or center stripping. That's the lazy man's way to crown. Be there when people do the pruning and make sure they are not topping. Make sure whatever pruning they are doing is an effort to improve the structure of the tree to avoid limb failures. 

If a tree has come out and you want to put in a replacement, should you take out the entire old root system?

I would strongly recommend it because there are some fungi that can invade the old stump, mostly oak root fungus. If you can get the old stump out without damaging other trees — remember the root systems of trees are interconnected — do that. Or plant the new tree away from that location if possible. When homeowners  are replacing trees, there are some guidelines on how to select trees in the nursery.

Is it better to wait until spring?

Actually, the time to plant here is between October and March.  Our limiting season is the summer.  You want to get root systems established before the heat of summer. You can also buy bare-root trees now and then you know exactly what you're getting. You can see it. If the tree is sold in a container, you can't really see what the roots are doing. You go to the nursery and think you are getting a good deal because you got the biggest tree, and often that is the tree that has the roots circling in the can or going through the bottom. Those roots never un-kink themselves. I like to plant trees small to establish them in my own soil. Some people aren’t so patient.

Rebecca Latta is based in Glendora.

— Jeff Spurrier

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Trees mission
Fallen eucalyptus at Mission San Gabriel Arcángel. Credit: Luis Sinco / Los Angeles Times.

Credit for photo at top of post: Irfan Khan / Los Angeles Times.

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