My favourite is Salvia leucantha ''Midnight'', the bush sage. Although a great evergreen shrub, it looks at home in the perennial border.
Foliage is silvery grey with a blue-green tint and the bush is smothered in rich purple flowers.
Height can be added to the border with lovely sky-blue flowers swaying gracefully on the long stems of Salvia uliginosa.
Bog sage grows up to 2m and has an open airy look. It does prefer a moist location but can cope in drier areas as well.
Also suitable for the back of the border is Salvia guaranitica ''Black and Blue'', the anise-scented sage.
Colour is all about contrast on this plant with rich green foliage and dark stems. Deep cobalt-blue inner flowers are cupped by their black outer calyxes, acting as floral frames.
It looks stunning planted beside the dark foliage of Dahlia ''Knock Out'' and ''Fire Mountain''.
Salvia azurea has sky-blue flowers. It is small, tends to have a sprawling, floppy habit and almost requires staking.
Try planting close to other plants for support. Most salvias do tend to spread but can be easily brought back in line.
Decide how much of the plant you wish to keep, then go around the outside of the clump, slicing through the roots, and fork out unwanted plant material.
If you do this each spring, you'll keep the plant under control.
Linda Hellyer is curator of the herbaceous borders at Dunedin Botanic Garden.
