Do cultivar and variety mean the same thing?

I notice that wine writers use the terms ‘cultivar’ and ‘variety’ almost interchangeably when referring to grape varieties. Do the two words mean the same thing? 

Yes. Botanists invented the word ‘cultivar’ as an abbreviation of ‘cultivated variety’, but the term is not used widely outside South Africa and the USA, where it seems to have taken root. The problem comes when you try to describe a wine made from one grape variety, rather than a blend of two or more. If you use the word ‘variety’, then the adjective is simply ‘varietal’, as in ‘a varietal wine’. How do you use ‘cultivar’ as an adjective? A cultivarial wine? ‘Cultivar’ sounds very professional, but ‘variety’ is probably the better word to use.