North American Fruit Explorers mailing list at ibiblio

[Joe and Ellen Hecksel <jhecksel@voyager.net>]

Young, fast growing trees tend to shed there outerbark more quickly 
since their girth increases by a larger percentage each year.  The 
lichens cannot get a toehold.  Trees that are older or are struggling do 
not shuck off their outer bark as quickly and lichens can colonize them.

> I have heard that lichens don't harm trees but may indicate a poor nutritional state. 


--
-Joe Hecksel
My personal web site: http://my.voyager.net/~jhecksel