The lamiaceae is a huge family. It has been subdivided into several subfamilies or sections. Members within a section or a similar grouping may possibly cross pollinate altho not likely. For example, if two Salvia species have the same chrosome number and flower at the same time in close proximity, there is a possibility that hybridisation might occur. I am certain that there are several good books in your local library that will offer a much more concise explanation. Plant genetics is an intensely interesting subject.I hope this helps a bit!

This did help quite a bit, thank you! I shall go check when I have a bit more time, but it seems likely that I could attempt come fun hybridization experiments.

"and flower at the same time"

Flowering at different times isn't a bar to artificial hybridisation, as pollen can be stored until needed.

Resin