Coceano offers a couple of options for overwintering your favorite Solenostemon (coleus) or Begonia cultivars. "First, consider digging up and bringing a plant indoors," he suggests. "Whether you call it a stock plant or parent plant, mature plants that have been growing outdoors all summer have substance to them, which translates into survivability through the low-light days of winter.
"Second, rooting cuttings is a tried-and-true method," he says. To improve the odds of success, Coceano recommends getting cuttings started during the warm days of summer rather than waiting until fall. "The cool days of autumn—typically when we start thinking about the coming frost and bringing plants indoors—trigger changes in plant physiology that result in reduced vigor and thus reduce rooting success," he explains. "Cuttings taken during the height of summer are vigorous and generate roots quickly.
"Finally, root your cuttings using whatever method you have success with. Some literature will tell you not to root in water, as cuttings don't transplant well. Truth be told, water works quite well for some genera—Solenostemon in particular." If you use water for rooting, Coceano says to be sure to transplant cuttings before the roots get too long. "When rooting in water, transplant before the roots have begun to circle around the container. Using a glass jar lets you keep an eye on the root development. I like to pot up cuttings, especially coleus, when roots are about 1⁄2 inch long. Diligence and observation are key."
Originally published in Organic Gardening Magazine, Oct/Nov 2013