Sun Scald

[TreeLogic]

Trying to understand this a little better.

• Does it happen to certain trees worse than others? If so, what bark characteristics are more inclined to damage?
• Is it like sunburn in humans in that a resistance can be built up, similar to people gaining more pigment in the skin?
• Anything else to add?

I ask these questions because I've noticed plenty of trees that have trunks exposed to the sun, yet they're showing no evidence of any growth or reactionary response. It seems more reaction takes place when a trunk area was once shaded, and then exposed to sunlight.

 

[Tree_Frog]

I'm not the smartest guy in this room or claim to be but I will try to answer your questions with my limited knowledge.

1. I believe that bark plays a role in this. Smooth bark trees seem to be affected more. I cannot say if I have seen too many say Aspen or River Birch become scalded. I have seen a number of Maples, Live Oaks here in Florida, California Live Oaks, etc.

2. Yes. Summer removals/pruning can play a part. If the tree is not used to direct sunlight it can get sunburn. So timing can play a factor when redesigning a landscape. Had a client loose a 30 year old dogwood when someone removed a large elm providing it shade.

3. Winter can play a role in sun scalding. The freeze and thawing of vascular tissue can break the cellular structure and create a wound. I have seen this in a lot of newly planted trees in Idaho when I was working there. Another thing that I have seen is reflected light creating a problem such as office building windows.

Transplants seem to take the worst beating. Take a look in a newly planted parking lot. Depending on the area, a large portion of the trees will be scalded on the same side. Does available water have a role in this? not sure. Good landscape companies will place that white guard around the lower trunk to avoid the scalding during the establishment period if it is an area of high scalding.

Very unscientific but I hope this helps.

 

[Leroy]

Good stuff treefrog. Maples get it bad around here as well. Cold/hot swings can get pretty extreme here in the winter.

I remember reading somewhere that trees do develop different tissues according to sun exposure. I was told that if you get a nursery tree or do a transplant you should try and keep it in the same orientation.

 

[Leroy]

Purely observation and speculation...

 

[Jeff]

Very common in maples, especially Norway, that have been V'd out or similarly topped/hacked for line clearance. All those interior branch top sides that hadn't been exposed to full strength summer sun before really take a beating.

 

[TreeLogic]

Great answers, thanks.
RE: "Very unscientific but I hope this helps." and "Purely observation and speculation..."
Hey, observation and speculation are the beginnings of scientific knowledge. Just because it aint published doesn't mean I take it with a grain of salt. Thanks again.
So with these answers in mind, and knowing that larger pruning cuts which face the sun, are less apt to compartmentalize properly, I'm wondering if the bad ol' pruning paint might help with these issues a little? Not so much for sunscald on the bark, but for the larger pruning cuts.

 

[Jeff]

Besides all of pruning paints other ills, won't black pruning paint absorb more solar heat and make sun scald worse? I'm totally guessing here, but...

 

[Tree_Frog]

Not sure if it affects the cut as much as the bark that is now being exposed.

 

[Jeff]

Good point, TreeFrog. We're not seeing the scald on the wood, we're seeing it on the bark.

 

[CutHighnLetFly]

looked at a Norway Maple for someone. a couple summers ago they had two other not as large Maples removed, which left the last one really exposed to sunlight. it was also in a courtyard with houses around 3 sides and nothing but brick patio underneath, it stays hot around the stem.
granted this tree was struggling as it was, with limited root space, but it is now it has bark splitting everywhere. main stem, every major lead, everywhere.
now, because of homeowner's limited funds and lack of his own foresight, it is now an unsafe, inaccessible (without a crane anyway) dying tree. i think this happened because of an Arborist's lack of foresight. maybe taking the two removals in stages, one at a time would have helped.

not answers to your questions i guess Will, just blabbing while one the subject. i certainly learned from seeing this specific situation.