Not an answer, but of oblique relevance...
I see John Whittlesey has written a book on Salvias (reviewed in the RHS 'The Garden' magazine, Nov14, p.98).
I know John through violets, and am sure his book will have been well researched and based on a good amount of his own experience as a grower and nurseryman (in northern California).
'The Plant Lovers Guide to Salvias', 2014, Timber Press, 2014 220pp