Missing snow

The vinca groundcover in our front yard emerged from this year’s mild winter looking ragged around the edges. Vinca (Vinca minor) leaves typically stay shiny and green through the winter, but this year some turned an unsightly brown. I’m guessing that this was due to lack of snow cover. With no snow to insulate them, the usually evergreen leaves dried up and died.

Last winter brought less than our usual snow accumulation

    Meanwhile, back in the vegetable bed, we lost two 21-year-old lavenders (Lavandula angustifolia). Despite their Mediterranean ancestry, they’d proven their ability to survive cold winters. What did them in, I think, was too little snow.

All that's left of a lamented lavender

    A blanket of snow keeps the temperature around plants relatively stable and protects them from desiccation. Plants that survive New England winters have adaptations that enable them to endure the cold. But frigid, drying winds can overwhelm their defenses when there’s no snow cover.

Consistent snow cover insulates plants

    I know we shouldn’t confuse weather with climate. One mild winter with little snow doesn’t prove a trend. In winter 2017-18 the nearby town of Milford recorded 87 inches of snow, in contrast to 47 inches this year. But we know there’s a change underway due to global warming. The Fourth National Climate Assessment, released in 2018, predicted that by 2035, the Northeast will be more than 3.6°F (2°C) warmer on average than during the preindustrial era.

Cairn in Snow, Caspar David Friedrich, 1807

     This compilation of government research also predicts less snow and a shorter snow season in our region. That won't be the worst effect of climate change, but it'll be one that gardeners will regret.

    I’ll replace the lavender plants that died with a variety such as 'Munstead' that reportedly survives winters north of us in USDA hardiness zone 4—we’re in zone 6b. 

Lavender 'Munstead'

But that won’t mean they’re safe without snow. If I want them to survive, I’ll have to remember to cover them with leaves or straw and then wrap them in burlap for the winter months. That’s more work than I had in mind, and it looks bad. I’m not a fan of burlap-swaddled lumps in the winter landscape.

I don't find this decorative

    The vinca in the front yard is on its own. There’s no way I can cover it up without creating an eyesore or sending mulch material blowing all over my neighbors’ lawns. Fortunately by May, this winter’s dead brown leaves had fallen off and been replaced by new foliage. I hope that will keep happening.

The vinca bounced back

    Garden plants’ tolerance for cold and heat are rated on two useful scales. The USDA Plant Hardiness Zone Map focuses on the lowest temperatures in an area. The American Horticultural Society’s Plant Heat Zone Map ranks areas according to the number of “heat days” over 86 degrees. For example, right now ‘Munstead’ lavender can grow in USDA hardiness zones 4 to 9 and AHS heat zones 5 to 8. 

     Who knows how a warming regional climate will change these facts of plant life? Maybe New Englanders will also need to learn to rate plants’ tolerance for winters without snow.