There are plenty of resources on salvia growing; mainly websites but also books. As growing conditions vary so much, it’s good to consult a reference from as close as possible to your own climate, as well as general reference articles on particular plants.
I am listing the resources I mainly use here partly as a bibliography for my posts. I use the standard surname system, indicated below in bold.
The classic salvia reference book is Betsy Clebsch‘s ‘The New Book of Salvias’ (2003), published by Timber Press. It seems to have gone out of print since her death, but is still available online, and here in Australia has been published (2008) by Florilegium. Betsy Clebsch had a garden near San Francisco, and gives excellent descriptions and growing advice for a large number of cultivars and species. There is also interesting background on many of the species. Plants are listed alphabetically with photos and line drawings.
A reference book currently in general publication is John Whittlesey‘s ‘The Plant Lover’s Guide To Salvias’ (Timber Press). This lists fewer plants than Clebsch and goes into less detail on each, but has larger photographs, and chapters on cultivation advice. John’s garden is in Northern California.
My go-to website tends to be Sue Templetons ‘Unlimited Perennials‘. Sue’s garden is at Albury in Southern New South Wales, Australia. The website lists a large number of salvias, including ones she has abandoned as unsuitable for cultivation. It is easy to navigate to each cultivar page, and they all have good photos, growing advice, etc. for Australian conditions.
The Victorian Salvia Study Group has an active site with an extensive list of salvias, photos and cultivation notes.
Perennial Poppies is another Australian group with an expanding website, this one based in South East Queensland.
Three comprehensive websites further afield from Australia are Rolando Uria‘s Salvias.com.ar from the Buenos Aires region, Robin Middleton‘s Robin’s Salvias from the UK, and Kermit and Vikki Carter‘s Flowers by the Sea from Northern California.
Rolando Uria is a salvia expert with an active collection and breeding program. His website (in Spanish but the right Search Engine will translate) has an extensive list of salvias, with many pictures of each variety and useful cultivation notes as well as descriptions.
Robin Middleton died in early 2020, but his marvellous website is being maintained. It’s a phenomenal resource. He lists over 600 species and cultivars, all with pictures. There is also growing advice for English conditions.
Flowers by the Sea is an active nursery and plant order business. North American growers will find their Salvia listing particularly useful.