hau Ellie,
I have seen two of those
trees, one was an oak in up state N.Y. it was alleged to be good luck to pound a penny into the trunk of this one particular tree.
When I got to see the tree (1967) there was no room to pound a "lucky" penny into the trunk, this was apparently started in the late 1700s and sometime around 1965 the tree had expired from copper poisoning, it had been left standing by the town of Newburgh N.Y. since to cut it down would have apparently negated the good luck. To me this was like the proverbial
rabbits foot, it certainly wasn't good luck for the tree just like the rabbit foot is not good luck for the rabbit.
The second "penny tree" I saw was in the mountains in California, in this case the tree was a ponderosa pine, it was located near Donner Pass. This tree was supposed to have had the pennies hammered in by those who made it over the pass, apparently the penny showed you made it over before winter set in and once again the copper poisoning took the tree's life. This tree was reduced to ashes in a forest fire in 1969, the copper pennies were melted into a mass that ran around the trunk's remains, the California forest service finally removed the trunk and copper mass in 1971.
I've read about how burying copper pennies in garden beds is supposed to be good for certain plants. The problem with this myth is that by the time metallic copper gets into the soil as molecules, those plants would be long gone and replaced many times.
Redhawk