Until around 2003 or so the only types of salvias I was aware of were the herbaceous sort. They were hardy, generally purple-flowered and bloomed towards the end of June for a few weeks; useful, but hardly exciting.
The first shrubby salvias I was aware of I saw at the Parham Plant Fair in July at Parham House. I bought several in various colors, but only one, greggii x serpyllifolia, survived the winter.
Over the years, as more and more appeared on the market, we found ones that were quite hardy and they became a main-stay in the flower beds, giving us good color over a very long flowering period.
There are two main species: greggii and microphylla. Greggii or Autumn Sage tends to be lower-growing and more compact.
Microphylla or Mountain Sage is taller-growing and leggier. Both start flowering very early in the summer season, which is the end of May here in Sussex, until frost in the autumn. .
The hybrids of these two species are called x jamensis and the named hybrids will take after either one or the other parent. There are now innumerable named hybrids and cultivars to choose from, although they do vary in vigour.
They should be treated much like lavenders; pruned in the spring after they start of fill out with leaves; either lightly or more severely, depending on the age of the plant. A light pruning in late August is also desirable. You may or may not deadhead them, but they will continue flowering regardless.
A note about color: I’ve noticed that some plants have very long flowering stems with the flowers spaced out and some have quite short flowering stems which concentrates the flowers and, hence, the color. For me, that is a very important quality and most of the plants I now grow have compact flowering stems giving lots of concentrated color.
Splendid plants and worth trying in lighter soils.
The bees adore them!