I think this is true. I live in Guadalajara, Mexico asking a plant tree or what ever using a scientific name is something imosible.
I had been studing the taxonomy of plants at this page:
http://www.ncbi.nih.gov/ its very usefull because you can get the official taxonomy classification, only change the box behind search to taxonomy and write the name of what are you looking. The point is that plant clasification is in constant chage and also scientific names are relative just like azaleas were reclasified from Azaleadendron to Rhododendron.
The best weapon is to study the factors that vary from each species.