Gardening with Jennifer: Snow and Ice in the garden

By Jennifer Rotermund

Spiraea weighted down by the heavy snow.
Photo by Jennifer Rotermund

Winters in the Pacific North West are unpredictable and present a special set of circumstances in our gardens. January around here can be wild and windy, snowy and icy or as mild as June (which is also a reflection of June in the PNW). But since we’re not as likely to deal with a lot of snow and ice - at least in the Puget Sound region - and therefore are taken by surprise when it actually happens, here are a few things to know about the impact of snow and ice on the garden.

Perennial flower stems left up to provide bird food during the winter.
Photo by Jennifer Rotermund

Snow provides insulation at the base of plants where frost damage can be the most detrimental. Unless a heavy snow fall is in danger of bending and breaking branches that aren’t likely to restore themselves during the subsequent growing season, snow may be left to fall and sit where it wishes. Consider it to be part of the beauty of the winter garden.

Yucca in snow.
Photo by Tom Bewley

Frost is more problematic - and potentially lethal - to our plants, especially in the absence of snow. The freezing of the roots of a plant and the surrounding soil can kill a plant, rather than the freezing of its stems and branches. This is where a nice mulch of leaves or compost on the soil creates that “warm blanket” effect. Plant cultivars finding their way into our local nurseries from warmer climates, such as California and the Mediterranean, are the exception to this and are also vulnerable to lethal die-back when their branches alone are exposed to a hard, prolonged freeze. These precious plants will benefit from the protection of an old bed sheet or row-cover cloth when temperatures fall below freezing.

Rainbow Chard cultivated by a local farm to withstand our weather.
Photo by Jennifer Rotermund

Water, in fact, once frozen in the soil, is no longer available for up-take by the roots of a plant. A prolonged frost can literally cause plants to die of drought in the middle of winter.

It was warm before the ice and snow
Photo by Lee Lageschulte

Finally, outdoor potted plants are extremely vulnerable to frost. Consider containers of soil and plants to be their own little micro-environment. Separated from the soil of the garden bed, potted plants don’t benefit from the naturally occurring heat of the earth itself. Likewise, a thin layer of plastic or ceramic (the walls of the container) does not insulate soil from frost. When temperatures drop, frost is likely to penetrate any side of a container exposed to the ambient air. If you can’t bring containerized plants indoors, cluster them together close to your house (clusters decrease the exposed surface area and your house gives off heat), water them well (before temperatures fall below freezing) and, if possible, cover them with a cloth at night.

Stewartia tree decorated by the snow
Photo by Jennifer Rotermund

Winter is also a great time to make plans for new additions to the garden in the Spring. Remember, native plants have adapted to our crazy weather patterns and need the least protection. For the greatest success with the least amount of work, I always start with native plants.

Jennifer Rotermund is the owner of Gaiaceous Gardens (an urban farming & wildlife gardening business with a teaching garden/urban farm and certified wildlife habitat/ sanctuary located in Shoreline). She is certified by the National Wildlife Federation as a Habitat Steward and is a Docent with the Kruckeberg Garden.

Previous Gardening with Jennifer articles can be found by clicking the link in the left column of the ShorelineAreaNews.