Columns, In the Garden

Managing Salt in the Landscape

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photo by Bonnie Kim Donahue
Although salt is beneficial in winter for deicing roads and walkways, it can be detrimental to trees, shrubs and landscape plants that are planted near salted roads or sidewalks.

by Bonnie Kirn Donahue, Extension Master Gardener, University of Vermont

NORTHFIELD – Salt can be a great asset in the winter for deicing roads and walkways. Salt prevents ice from forming by lowering the freezing point of water, creating safer surfaces for people to walk and drive on.

However, salt can have a detrimental impact on woody and herbaceous plants in the landscape. Salt can impact plants in a number of ways.

Salt spray that splashes off salted surfaces can coat the outside of a plant’s stems or leaves. It is corrosive and can burn leaves, stems and even buds, impacting flowering in the spring.

Salt on the soil surface can soak into the soil and become absorbed by plants. Once absorbed, it pulls moisture from plant tissues and dehydrates plants from the inside.

Luckily, there are things that we can do to mitigate these impacts.

First, for existing garden beds that are close to salted roads or sidewalks, flushing the soil with water in the spring is one way to clear salty build-up from the winter. Spring rains may provide enough water to leach the salt from the soil naturally, but watering the plant bed one or two times in a dry spring might be all that is needed. Be careful not to overwater the bed to avoid soil erosion.

Second, when selecting sites for planting new garden beds or trees, it is critical to consider potential salt exposure. Planting trees, shrubs and perennials near salted surfaces creates the possibility that plants will struggle, so consider what is adjacent to your garden bed or tree.

Finally, in areas where you can’t avoid salt exposure, select plants that are more tolerant of salt.

For trees, several native oak species have some salt tolerance, including white (Quercus alba), red (Quercus rubra) and swamp white oaks (Quercus bicolor). Native shrubs such as winterberry (Ilex verticillata), black chokeberry (Aronia melanocarpa) and nannyberry (Viburnum lentago) also are known to have some salt tolerance.

Perennials such as daylilies (Hemerocallis spp.), catmint (Nepeta racemosa) and yarrow (Achillea spp.) perform well with exposure to salt.

Research on salt tolerance of plants varies, so look for cooperative extension resources in your area online, or ask your local nursery or greenhouse grower for advice.

Salt is a reality of winter, but it doesn’t need to ruin your garden in the spring. Try these tips and see how you can have the best of both worlds.

[Bonnie Kirn Donahue is a UVM Extension Master Gardener and landscape designer from central Vermont.]

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