~Chet Graver, Columbus, Indiana
A. In general, plants that are healthy and appropriate for the site where they are planted will survive dry winter months without any supplemental watering. Winter tends to be dry in the northern temperate zones “because when the ground is frozen, water can be tied up. Also, cold air is dry,” notes Susan Tantsits, horticulturist and co-owner of Edge of the Woods Native Plant Nursery in Orefield, Pennsylvania. “If a plant has leaves—broadleaf or needled evergreens—they can still transpire water during bright, warm days, but the roots cannot take up water if the ground is frozen.” Some evergreens have waxy leaf coatings to reduce water loss during the winter, while others, such as rhododendrons, may roll their leaves to conserve moisture, Tantsits explains.
So the danger to plants is desiccation from transpiration through the leaves and lack of water available via the root system. “The most important thing I have learned,” says Tantsits, “is that plants should not be suffering from dry soil going into the winter; that they should be well hydrated before the soil freezes.”
Choosing landscape plants that are hardy in the zone where they will grow, and also well suited to the local climate, is preferable to nursing inappropriate selections through the winter. “This is why we identify plants as being appropriate for different hardiness zones,” Tantsits says. “A plant that is not indigenous in a landscape may need [supplemental] watering more than one that is adapted to the local climate.”
Photograph by Laurel Scherer
Ask Organic Gardening is edited by Deb Martin
Originally published in Organic Gardening magazine, February/March 2013