This is a very tough South African plant and adapts to quite poor garden situations. It grows in my letterbox garden at the top of the driveway, which rarely is watered. It grows to about 50 cm and has dainty pink to lilac flowers from spring till autumn, giving a pretty effect. It is one salvia which I find self-seeds a lot and is a bit weedy. Its companions in its dry garden bed are lavenders, rosemary, perennial wallflower (Erysimum species), Verbena, evening primrose (Oenothera species), Gazania and Lychnis coronaria. Salvia scabra is said to be one of the parents of the beautiful new sky-blue flowered Salvia 'African Sky'. It will tolerate light frost.
Postscript: In the end, this plant died out and I didn't replace it. It isn't one of the most desirable Salvia plants, in my experience.