I am slightly puzzled as to when a common name is applied to a plant. As an
example the genus 'EUONYMUS' has the common name Spindle tree' does this now
mean "E. f. Emerald 'n' Gold" for example has this as one of its common
names?

Another example would be 'BUDDLEJA davidii' common name 'Butterfly bush'
does this common name only apply to 'davidii' or does it apply to all
varieties of 'davidii'?

regards
Pat