Iris Cohen writes
But if you call Pinus sylvestris Scotch pine, the
British bonsai growers have a fit. Outside the US it is Scots pine. I have
tried to explain that it is listed that way in American dictionaries, but
they
insist the dictionary is wrong (not understanding the function of a
dictionary).

Stewart Robert Hinsley schreef
"In the North of England and in Scotland, _Scotch_ is not used outside
fixed expressions such as _Scotch whisky_. The use of _Scotch_ for
_Scots_ or _Scottish_ is otherwise felt to be incorrect, esp. when
applied to persons."

I don't understand the reasoning, but there a body of opinion that
"Scotch" is not only incorrect, but also offensive.
--
Stewart Robert Hinsley

+ + +
There is such a thing as a separate Scots [?] language, a form of Gaelic.
Perhaps it stems from there ...

However such things are hard to judge: IIRC the Scottish kilt in its present
form was an English invention imposed by force on the Scots. Yet it now is,
apparently universally, accepted as a badge of Scottish identity.
PvR