From this NGA page:

https://garden.org/courseweb/c...

This is no longer correct, under the more recent versions of the ICNCP the abbreviation cv. is not to be used.

"Another way to indicate a cultivar is with the abbreviation cv. instead of the single quotes—for example, Cornus florida cv. Bay Beauty."

Thanks Sue! I updated the page to read it as:

An older (and now obsolete) way to indicate a cultivar is with the abbreviation cv. instead of the single quotes - for example, Cornus florida cv. Bay Beauty. This method should no longer be used, but is mentioned here for educational purposes.