Plectranthus hail from warm temperate to tropical areas of the world (particularly South Africa) 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.
One tall species is Plectranthus barbatus (sometimes referred to as Plectranthus grandis), growing around 2m tall. It has thick, furry leaves with a pungent scent, and it sends up intriguing plump buds which open to beautiful, long, bright blue spires of flowers, the bluest of all the Plectranthus. It begins to flower around late March and continues into winter, and may even rebloom in spring if deadheaded. It looks attractive grown nearby a mixture of the shrubby purple-blue, pink or white Plectranthus ecklonii, Camellia sasanqua or cane Begonia, with an underplanting of some of the groundcover Plectranthus. In African countries, it is apparently sometimes used as a hedge between fields.
It can grow in sun or light shade. It tends to sprawl to some extent so needs to be regularly tip-pruned in spring and summer to keep it a little more compact and promote more flower spikes. It should be cut back fairly hard in early spring after it has stopped flowering, and kept dead-headed through its long blooming period. It 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 can be very easily propagated from cuttings in spring and summer. All Plectranthus need to be replaced by new cuttings every so often as they get a bit straggly after a few years.