Unless you take precautions beforehand, that first bout of cold weather or frost will quickly kill off your coleus plants. Therefore, winterizing coleus is important.
Wintering a Coleus Plant
Overwintering coleus plants is actually quite easy. They can be dug up and overwintered indoors, or you can take cuttings from your healthy plants to make additional stock for next season’s garden.
How to Keep Coleus Through Winter
Given adequate light, coleus overwinters easily indoors. Dig up healthy plants in the fall (usually August), just before cold weather hits. Make sure you get as much of the root system as possible. Pot your plants in suitable containers with well-draining soil and water them thoroughly. It may also help to trim back the top half of growth to reduce shock, though this is not required.
Allow your plants to acclimate for about a week or so prior to moving them inside. Then place the newly potted plants in a sunny location, such as a south- or southeast-facing window, and water only as needed. If desired, you can include half-strength fertilizer once a month with your regular watering regimen. You may also want to keep new growth pinched to maintain a bushier appearance.
In spring you can replant the coleus back in the garden.
How to Overwinter Coleus Cuttings
Alternatively, you can learn how to keep coleus through winter by taking cuttings. Simply root three- to four-inch cuttings in late August (or prior to cold weather) by potting them up and moving them indoors.
Remove the bottom leaves of each cutting and insert the cut ends into damp potting soil, peat moss, or sand. If desired, you can dip the ends in rooting hormone but you don’t have to since coleus plants root readily. Keep them moist in bright, indirect light for about six weeks, at which time they should have enough root growth for transplanting to larger pots. Likewise, you can keep them in the same pots. Either way, move them to a brighter location, such as a sunny window.
Note: You can even root coleus in water and then pot up the plants once rooted. Move the plants outdoors once the warmer spring weather returns.