Interesting statement in TCIA magazine article

RyanCafferky

RyanCafferky

Been here a while
Location
Hood River, Oregon
Observational Forensics of Sick Shade Trees was an interesting article.

In his never ending list of possible maladies trees can have and their symptoms he had this one that I found rather ridiculous.

“Lichens and mosses can be like the canary in the coal mine for a tree. With few exceptions (such as the base of aged trees and the limbs of live oaks and maples), this is an indicator of stress in a tree. Healthy trees normally slough off bark before these non parasitic plants can get a foothold. “

Did anyone with any tree knowledge review this article? Lichens and mosses can be pretty ubiquitous in a lot of trees and in my experience have zero negative consequences or zero indication of tree health issues. Lichens are actually a sign of really good air quality and will grow on almost anything given the chance. Here in the northwest we have moss on many species of trees. Sometimes it is inches thick.

Would love to have other people chime in on this one.
 
I think blanket statements like this are horrible. Yet I do somewhat agree they can be sign of a slower growth rate. Many times it’s no biggie here in the PNW, but sometimes we SEE MORE on a stressed tree. Frequently in the twigs, sometimes it’s just because the tree is thinning in the crown. This could be a slow decline and the thinning is allowing more light allowing for more epiphytic growth. Or maybe it was already there and we are just seeing it more clearly.

I totally associate more lichen growth on the twigs within slow decline within laminted root rot pockets. Maybe the short internode lengths provide a better habitat?

So in short statement like this require a paragraph of explanation, I’m surprised at how many clients still call regarding moss and lichens thinking their tree is dying.
 
I agree that lichen more frequently grows on dead or dying limbs, and I frequently see it on firs, alders and b.l. leaf maples. That said, the problem is people misattribute cause and effect: they think the lichen/moss is killing the tree, rather than lichen/moss growing on things that are already dead and dying.
 
I have heard this and assumed that lichens can be an indicator of a struggling tree. in one particular species and situation here in the piedmont of nc.
Red maple planted in parking lot islands is the scenario I see that here. A species that really wants water and put into a stressful situation with way too much heat begins to shrink its canopy to cope. The lichens land on the branches and have good conditions to thrive, with some shade but also enough light . Certainly not a death sentence but I have seen trees with more lichen than leaves. Gloomy scale is also often hanging out in this scenario too. I don’t know this for a fact though, just my anecdotal observation
I can see what you are saying though. I also would not make a blanket statement about lichens . I did not read the article, just commenting on your notes.
 
Does acid/alkaline balance come into play? Put an alkaline source on or near moss, lichen either directly or by root uptake and watch them decline or die. (Powdered clam shell in this instance.)

In the ocean they find a modest change in acid condition to make a huge difference to certain species of sea stars etc. (I think coral die off is related to this as well.)
 
Converse is also very true in the PNW, lack of moss or lichens can certainly be a sign of environmental stress. Which the tree is also subject to.

Also I really admire lichen on red alder, I’ve noted some vast regional differences. Just less than 20 miles on the east side of the peninsula I had to double take to make certain it wasn’t a different species of alder. Nothing serious just a fleeting wtf, kinda moment.
 
Merle Nelson said:
Does acid/alkaline balance come into play? Put an alkaline source on or near moss, lichen either directly or by root uptake and watch them decline or die. (Powdered clam shell in this instance.)

In the ocean they find a modest change in acid condition to make a huge difference to certain species of sea stars etc. (I think coral die off is related to this as well.)
Click to expand...
That and air chemistry plays a huge part.
 
Pretty well agree with the above comments...a conversation we have regularly with clients:
1) if the tree is thinning because of other causes, lichens may get thicker.
2) if the tree is sloughing off less bark, it may be an indication of slower growth...but that's a MAY - certainly wouldn't use the same measurement on Bur oak and Sycamore. Like @Neill said (great example, by the way) knowing what is "normal" for the species of tree and setting is important.
3) generally I consider lichens indicator of healthy environment and overall beneficial more than harmful (minor benefits to tree health when rainwater washes nutrients off into the soil, more significant benefits to wildlife)
 
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