Hello Awol,
I've corrected 2 remarkable trees with the tag "denotation=park" (replaced by denotation=natural_monument [1]), because this tag is not documented and it doesn't identify that the trees in question are remarkable.
I then came across your map instructions page for trees.
What do you think about changing your recommendations for the "denotation" tag?
It might be interesting to discuss this on the wiki or on an OSM forum?
Well done for all the work you've done, and I look forward to sharing our common interests in trees and cartography.

[1] see : https://wiki.openstreetmap.org/wiki/Key:denotation 