Janet Baraclough wrote:

(snip)

"Butterfly bush" is the common name that encompasses all
buddlieas..if you're in the UK. It's naturalised in the UK, and has a UK
common name.

(snip)

You will also find that in other countries the common name is the same
as the common names in the UK which means the exact description of the
plant without naturally where it's from, where it grows etc which is
more specified using latin. Butterfly bush will be in French 'arbre a
papillons', meaning the same thing. There are some slight differences
which are amusing, depending on the culture, for example a 'foxglove'
would be in French and Spanish 'a woolf glove'. I've found myself
knowing a lot more plant names in English than French and use a pure
translation of the English common name to describe what I'm referring
to if the person doesn't know the latin name. It works all the time.