Hailing from South-east Asia, coleus - now known botanically as Solenostemon scutellarioides - have become fashionable again in recent years and they offer a rainbow of foliage for gardens. They belong to the Lamiaceae plant family, and whilst some sorts are very cold sensitive and perish even in our mild winters, there are many which keep going from year to year, as they are strictly speaking a bushy perennial. Though they are very useful for bringing colour to shaded spots (including full shade), there are some modern cultivars that thrive in sunny areas, extending their usefulness. They grow best in a well-drained soil with adequate moisture and regular liquid feeding; but they survive surprisingly well in dry spots once established. Mulching will help keep their roots cool and moist in summer. Their multi-coloured leaves have endless potential for creating 'colour echoes' with nearby flowers or foliage of the same hues. They work very well with 'tropical'-style plants.
The leaves may have contrasting coloured edges, freckles, bands or other markings; leaf shapes vary from long and pointed to rounded or finger-like or even what is termed 'duckfoot' by coleus fanciers. Almost every imaginable colour can be found in some coleus or other! I don't know the name of any of my coleus plants, but there are many named cultivars. Heights can vary but they are usually around 60 cm tall. Some forms have a trailing habit. The best way to acquire good doers is from other gardeners, rather than growing them from seed or from punnets bought from nurseries. They grow very easily from cutting and will even sprout roots in a glass of water. I usually take cuttings of my favourite ones each autumn, as a precaution against losing them in a very cold winter. In very cold areas of Sydney, they may not survive winter, so taking cuttings is a good idea. They can also be grown from seed, and some gardeners report them coming up by themselves by self-seeding in the garden, although I have never had this happen.
Pinch out the growing tips regularly to encourage a well-branched plants and remove any flower stems which develop, as these make the plant look lanky. Also, stems that bloom tend to die back. Those coleus that do survive can look sad by the end of winter, but don't cut them back whilst the weather is still cold as it can kill them - I wait till early September before cutting them back and fertilising them with a general purpose food. In general, though, I think it's best to start them from overwintered cuttings each year. Coleus can be grown in containers or hanging baskets. It is even possible to train a standardised coleus! For lots of information and ideas on coleus, I can recommend the book Coleus: Rainbow foliage for containers and gardens by Ray Rogers.
Note: This plant has been renamed Plectranthus scutellarioides.