The already healthy basal foliage is an indication that you can cut off the flower spikes when they are finished. Then they will no longer be a drain on the plant, and it will put its energy into fresh growth.

I just sheared mine 6/2 in Pittsburgh, PA. It's flowers fade or shed from the bottom up. I used my hedge trimmer this year, but pruners last year. I sheared down to the leaves.

I I planted Hairy Vetch, a cover crop last September. That brought nitrogen. I allowed it to intertwine with the Salvia. I got a lighter purple color from the Vetch. The Bumblebees really enjoy the Vetch. The honeybees enjoy the Salvia.

I anticipate (2) more shears for the summer.