Sorrry if this is an elementary question but I bought this salvia plant which I planted about a month ago (late May). Watered it well and consistently, it was a bright beautiful purple for a while and now it's died back. Will it rebloom on its own? Do I deadhead or shear to rebloom? And if so how soon will it rebloom?

I see the same plant in my neighborhood and they are still blooming. I was hoping to have blooms all summer.