If you are unsure of the cultivar/hybrid, go with the species. If you are unsure of the species, use just the genus.
A botanical name is: Genus species 'Cultivar'
An example: Ficus elastica 'Ruby'
If I don't know whether it's a 'Ruby' or not, I would list it as F. elastica. If I'm not sure my ficus is from the elastica species, I would list it as just Ficus.
