Latin, if there is any need whatsoever to specify what plant you're talking about.
However, once we agree on what plant we're talking about, any old nickname is sufficient, and often easier to pronounce or more fun. And no one thinks you're "putting on airs" for being exact.
I can testify that almost ANY given common name has several, or dozens, or even hundreds of plants that have been called that. They may be unique and specific names regionally, but as soon as you step outside one region, "tickseed" could mean many different things spanning six genera.
"Kiss Me Over The Garden Gate" is a fun name, and only applies to two species as far as I know, but anyone in any country can look up "Persicari orientalis" or "Persicaria amplexicaulis" and know whether it is a 6"-12" Zone 5 perennial or a 36"-48" Annual. Which I would like to know before putting a lot off effort into establishing it!
You can call me Corey or Rick or Dick or Rich or Ricky, even though there are millions of "Rick"s and thousands of "Corey"s.
But when it MATTERS who I am, like whether I've paid my taxes or received a specific med or which "Rick" it is that the Governer just pardoned, I want Richard Thomas William Corey, SSN 123-456-7890 to get that reciept or that pill or that pardon!
For example, when trading or giving seeds away, if the first person who gives it away only includes an ambiguous name, anyone who grows it or its descendents will have to say "yeah, it's pretty and looks kinda like this or that, but I have no idea what it is".
I have a small yard and I don't grow any NO_ID seeds.
To some degree, if you know a Genus or Family name, you have some idea what to expect and how to propagate or care for it. And you can look it up, and benfit from the experience of generations of gardeners.
