What I've learned about trees (but don't take my word for it)
Ancient trees can be measured in hugs for eg a three hundred year old oak tree would have a girth of three adult hugs.
There are no native trees in Iceland.
Rowan is known as the witch's tree - it is no relation to Ash - historically, one was planted by the front door to provide protection from dark forces.
The bark of Yew is used to treat cancer but the needles are poisonous
Apple trees rarely grow from a pip.
Birch trees provide a watery elixir in spring - it can be tapped, collected and consumed as a tonic.
The life cycle of a leaf is determined by the hours of day light; as the days grow shorter the chemicals that activate photo synthesis withdraw from the leaf causing the reds and oranges that signal autumn.
... to be continued