Plectranthus hail from warm temperate to tropical areas of the world and grow in shadier parts of the garden under trees in very ordinary soil where many plants do not thrive. They grow quickly and are tolerant of drought and root-competition.
Plectranthus ornatus is a shrubby groundcover from South Africa. It is very similar to a couple of other Plectranthus species but I am hopeful that this is the correct name for it (the alternatives being Plectranthus neochilus and Plectranthus caninus). It was one of the first plants I grew in my original garden, given to me by my mother as being indestructible and easy to grow!
It has quite succulent, rounded, grey-green foliage, which has an unpleasant smell and is said to deter dogs from gardens! It grows about 20-30cm tall and spreads to about a metre wide. It has chubby flower spikes which are purplish-blue in colour which appear in autumn and sometimes unpredictably at other times of the year. It can cope with sun (as it is semi-succulent, unlike the softer Plectranthus species) or shade, and tolerates extremely poor garden positions. It flowers best in full sun. I think it looks best with other very drought-hardy plants such as Artemisia, rosemary or lavender. It can look effective cascading over a sunny wall.
The stems should be cut back fairly hard after flowering (or in early spring in cooler areas if there is the risk of frosts). The plant dislikes hard frosts, but if grown under a canopy of trees, will usually be well protected from milder frosts. It enjoys being mulched and fed occasionally. It is very easily propagated from cuttings in spring and autumn. All Plectranthus need to be replaced by new cuttings every so often as they get a bit straggly after a few years.