help! wood rot in beloved palo verde

lotagrassMarch 27, 2009

We have a young palo verde we planted in our backyard in Glendale 2 + yrs ago. It was a 5 gallon froma local nursury, not sure of the variety. It had grown very fast, maybe 15 ft tall and WAS gorgeous - our favorite element in the garden. Last night's wind storm ripped off half the tree and it is now precarious and assymentrical (no tree/shade left in the yard - only a part hanging over the wall).

Anyway, the trunk is split about a foot up, as if by lightening, but at the joint of the two main braches where it initiially broke the wood is dark throughout and I see a little evidence of white mold hyphae? The wood above and below this spot looks fresh and healthy yellow. Such a shame, apparently my husband inadvertently was giving it too much water by backwashing the pool in that area. We're not sure what to do.

Can the wound be painted over with something to kill the mold/prevent its spread? How should the splintered trunk be trimmed? Will the tree eventually grow back in the direction of the yard? Should we just take the whole thing out and start over? We really can't afford an arborist, or even a gardener to prune/remove stump etc. Plus, my husband and I are academic ecologists, ought to be able to handle this ourselves with the right advice. Anyone have experience with this?

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petzold6596(8b southern NM)

To grow that fast, the tree would have to had far more water than it gets in its native desert environment. Palo verde wood is not very ligneous so it is susceptible to rotting if over watered. To bad, they are beautiful trees.

    Bookmark   March 30, 2009 at 10:20PM
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It sounds like your tree may have had what's called included bark. It is common in branch attachments that are narrow or less than 45 degrees. Some tree varieties are prone to these weak attachments. Instead of the bark being pushed up in the branch angle, it rolls in. Instead of a wood-to-wood connection in the branch union, it is replaced by bark-to-bark and the strength is compromised. Strong attachments are characterized by a branch bark ridge, or area of tissue that is 'pushed' up in between the branches or branch and trunk.

For now you can trim away the torn wood and leave the wound as clean as possible. Do not use sealants of any kind as these trap pathogens against the tissue in a dark, damp environment - perfect for decay. You can spray the wound with a 10 percent bleach solution if you like.

Your tree may recover but my fear is that the strength of the remaining trunk had been weakened. When a branch tears in this manner it usually takes a portion of the branch or trunk next to it, sometimes leaving only one-half of the former volume.

Should you decide to replace the tree, look for one with strong branch unions. If you select a native tree (mesquite, palo verde, acacia, ironwood, etc.,) be sure to water appropriately for the species. Remember that trees that grow rapidly typically have weaker wood than those that grow slowly (oak vs. mesquite for example).

Here's a link to information on watering landscape plants. On page 14 is a guide for newly installed plants.

Let me know if you have any questions.

Good luck.

Certified Arborist

Here is a link that might be useful: Landscape Watering by the Numbers

    Bookmark   April 3, 2009 at 11:55AM
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