Tradescantia Andersoniana Group Red Grape is the accepted RHS name for the hardy cultivar often sold under the invalid hybrid name x andersoniana.
A compact tuft of slightly fleshy grey-green leaves carries upright stems and vivid reddish-purple three-petaled flowers with yellow stamens.
Grow it in fertile, moist but well-drained soil in sun or partial shade, with afternoon shade in hot summers.
Cut back after the first flush for fresh growth and rebloom, and wear gloves because the plant may act as a skin allergen.