The recent (and rather late) arrival of snow in Boston makes some people happy, but it gives many of us chill-inducing flashbacks to last winter’s record-setting snowfall (Boston’s final tally was 110.6 inches!). I certainly don’t want to see another winter like that, but for the sake of my garden plants I welcome the light blanket of snow now covering them. Snow, particularly when it’s dry and fluffy, is an excellent insulator. It holds in the earth’s heat, and as little as an eight-inch layer of fresh snow can result in a relatively balmy 32-degree F temperature at the soil surface even when the air temperature is below zero. Consistent snow cover can prevent cold air penetration into the soil (important because the roots of temperate woody plants are significantly less hardy than above-ground parts) and also limits the freeze/thaw cycle that can push shallow-rooted plants out of the ground.
But snow can also have detrimental effects on woody plants. The main threat is for branch breakage from heavy snowloads that occur when dense, high-water-content snow accumulates on horizontal branches. Aging snowpacks also pose a threat–last winter a lot of breakage occurred on shrubs when branches were caught and pulled down in the crusted surface of settling snow, then had additional feet of snow piled on top. And while the subnivean zone (the unique environment at the juncture of soil surface and snow layer) provides protection for a number of animals, critters like voles can do a lot of damage by chewing tender bark at the base of young trees (apple and other fruit trees are favorites) while sheltered under the snow.
Moving beyond the physical reality of snow, let’s take a look at the etymology of snow in the scientific and common names of some plants here at the Arboretum. The Latin root for snow is niv-, and it can be found in the names for snow pear (Pyrus nivalis, 627-59), white-flowered cultivars of flowering quince (Chaenomeles speciosa ‘Nivalis’, 383-83) and American wisteria (Wisteria frutescens ‘Nivea’, 225-2002), and snowdrop (Galanthus nivalis), the charming little flowering bulb that dots the Arboretum in early spring. The Greek root for snow is chion-, seen most notably in Chionanthus [pdf] and aptly describing the snow-flurry-like floral display of North American native white fringetree (C. virginicus) and its disjunct relative, Chinese fringetree [pdf] (C. retusus). Snow shows up in common names like snow-wreath [pdf] (Neviusia alabamensis, 398-96), snowberry (Symphoricarpos albus), and Japanese snowbell (Styrax japonicus) as well as cultivar names for an oakleaf hydrangea [pdf] (Hydrangea quercifolia ‘Snow Queen’, 318-94), both a Loebner magnolia (Magnolia x loebneri ‘Spring Snow’, 260-73-A) and a flowering crabapple (Malus ‘Spring Snow’, 676-66-A), and Rhododendron ‘Boule de Neige’ (“snowball” in French).