Salvia nemorosa 'Caradonna' has mounds of textured green leaves and dense spikes of dark-purple flowers in summer. It is a long lived hardy perennial, meaning it should come back every year and it grows reliably to about half a metre. To plant it just make a hole in the soil and place the root-ball in it, cover with soil then firm down and water well. You can buy one or two plants with this order.