>(...) This use of unofficial names (esp. if
> different in different countries) may result in considerable
> confusion in cultivation.
Yes, indeed (not only in cultivation!). This is one of the main reasons why
an international code of botanical nomenclature (ICBN) was established.
>(...) What are the conventions on naming
> such plants until officially named?
The conventions are very simple, transparent, and straightforward:
*First* publish a validating protologue effectively (& deposit a type
specimen somewhere) and *then* start talking about (or even selling) the
stuff, *not* the other way round. Alternative procedures are not provided.
Kind regards
Jan