I have found that these European Salvias are best replaced every 2 or 3 years, another which can make a gaping hole in the middle of the plant is Salvia verticillata. Also, they seem to prefer poor rather than rich soil, and excellent drainage. Also dead-heading will encourage more flowering stems. In England, we have had a very wet summer, there has been a little mildew, and some of these forms have sprawled and got untidy. May Night and Caradonna, usually stay more compact for at least 2 years.

In USDA zone 5 in western Massachusetts back in the 70s, I had little trouble with Salvia nemerosa East Friesland. It had excellent drainage and full sun. I had to deadhead as Robin mentioned. Those years we had moderate summer rain. Heavy rains may have been the source of your problems this year and last.

I've deadheaded, and it hasn't seemed to make any difference.

Deanna

I would try dividing and replanting the salvias next spring. It sounds as if the plants have grown into clumps of many stems. Take each plant, dig it up, divide it into perhaps four or five smaller pieces, each having a handful of stems, and replant after you have tilled the bed. You'll end up with lots of extra plants or a much larger bed of salvias, but either way you be starting fresh and might get the good results you saw the first year. I don't grow any of the salvias you listed, but when I divide and replant my Salvia guaranitica, I often get better results the first couple of years than I see in later years. I think they grow better in tilled, fertilized soil. I am in zone 5 or 6 in PA.

I just flat haven't had luck with many of the bluer-colored sages. I've had much better luck with ones that are reddish, pinkish, and/or white. May night croaked in my garden the first year. Maybe try some different varieties?

My rule of thumb has been this: if it dies or looks bad, pick something else until you find something you like. Then, plant more of that which does thrive.