Sports vs. seeds
While most of the named cultivars we see for sale at this time of year are the result of sports that have been vegetatively propagated through cuttings, there are also many seed strains available (the Kong series for instance), and numerous new coleus varieties have arisen from traditional breeding programs using seed. The major difference between coleus grown from named cultivar cuttings versus those grown from seed is that seed strains are likely to flower earlier and more prolifically than cuttings, and will show wide variability (i.e., plants won’t look identical) while cuttings are usually indistinguishable from their parent plant.
Where to plant
Coleus are equally at home in beds or in containers. They require rich soil with good drainage to achieve their full potential; container plantings should be fed regularly with a balanced fertilizer (e.g., 5-5-5). Most coleus grow best when the soil is reliably moist but not waterlogged. Some coleus
prefer shady conditions while others will thrive in full sun, so site according to your cultivar’s requirements. Avoid exposed, windy situations that will leave coleus leaves looking like tattered flags.
Taking coleus cuttings
Coleus cuttings may be taken in late summer; they are easy to root in water, and once the roots are three to five centimetres long, they should be potted up using a soilless mixture for indoor plants, and overwintered in a bright, sunny window area. Alternatively, “mother plants” may be cut back and overwintered inside—just be sure to give them a good wash with insecticidal soap before bringing them indoors in early autumn. Apart from snails and slugs, coleus are largely insect and disease free when grown outdoors, however, pests like aphids, whitefly, spider mite and mealy bug may become a problem on overwintering plants, so monitor them conscientiously.
Personally, I no longer save coleus from one year to the next; they are relatively inexpensive to buy, and there are hundreds of exciting cultivars available, so I like to experiment with new ones each year—and I’ve yet to be disappointed.