Hi Tseeker, tree sap can be pretty mineralised,
and the issue of detectors detecting the roots has been around for some time.
Charles Garrett mentions this problem in more than one of his books.
Talking about mineralised tree root sap, I read a story regarding a deep dig ~ chasing a signal years ago.
They dug and dug, following the beep __ found nothing !!!
When they did some investigating it appeared that the spot where the signal was coming from years before was a stable,
this stable was there for years and years, they worked out the the horses peeing on the floor of the stable
resulted in a big sphere of highly mineralised soil, ~ turns out that the mineralised soil causing this "ghost" signal...
I haven't had a problem with detectable tree roots in the past few years,
maybe the more modern detectors don't have this problem.
Could possibly be a coil issue too!
