Minimize Deicer Damage with Salt Tolerant Plants
When we think of the effect that winter has on our gardens, we usually think about how bitterly cold it gets. The depth of insulating snow for our plants is another concern. We worry about ice storms breaking the limbs of our trees and shrubs. However, there is another problem that we must consider: salt damage to plants from deicers. It is crucial that we are safe when we drive and walk during the winter; thus, we need deicers. The most efficient, inexpensive, and widely used chemical for melting snow and ice is common rock salt, sodium chloride. But this salt may negatively affect many of our plants.
There are two kinds of damage from the deicers that we apply to our roads and walkways: salt spray and soil-borne salt. Salt spray can travel up to 1000 feet from salt-treated roadways by fast-moving traffic and the wind. This spray pulls the water out of the leaves of conifers and from the buds of deciduous trees. Salt spray is especially damaging in the late winter and early spring when leaf buds are beginning to swell. Often, the leaves and flowers on the side of the tree or shrub facing the road do not open or are stunted because of this drying salt spray.
Soil-borne salt damage occurs when the deicer from a road or walkway accumulates in the soil from salt-laden runoff as the snow and ice melt. The amount that accumulates is affected by the type of soil and its drainage. Soils that are higher in clay can hold more salt than sandy soils. Unlike a salt spray, soil-borne salt injury develops slowly over time and causes many complications for plants. Salts absorb and bind tightly with water, preventing roots from absorbing water. The salt can even pull water from the plant, creating a drought-like condition. At higher concentrations, sodium will compromise the absorption of essential nutrients such as calcium, magnesium, and potassium. With increasingly poorer health from salt damage, the plants become more susceptible to insects and diseases. Diagnosing soil-borne salt damage can be difficult because symptoms are common with other problems. These symptoms include browning along the edges of leaves, wilting, stunted growth, small, chlorotic (yellow) leaves, and early fall coloration and leaf drop.
What can we do about salt damage to our plants? First, take steps to minimize it. Try using anti-skid products, like sand, instead of salt when possible. Calcium chloride, potassium chloride, and magnesium chloride deicers are less harmful to vegetation than salt when used as directed. Move plantings away from areas where salt spray or salt-laden runoff accumulates. Alternatively, install plants that are salt-tolerant and avoid salt-sensitive species. If your plants have been damaged by soil-borne salt, applying gypsum (calcium sulfate) in the spring will replace the accumulated sodium ions from the rock salt in the soil. Gypsum will not change the pH of the soil. Gypsum has the added benefit of improving the texture of clay soils. Apply at a rate of 40 lbs. per 1000 sq. ft. You can also add organic matter to the affected soil and avoid using inorganic fertilizers. The soil can also be drenched to remove the salt. Six inches of water will leach out 50% of the salt.
The good news is that salt-tolerant trees can protect salt-sensitive trees from salt spray. Often, a windbreak or sound barrier of arborvitae (Thuja occidentalis) is planted along a road. Arborvitae may not do well as they are very salt-sensitive. Instead, plant a row of eastern red cedars (Juniperus virginiana), which tolerate both salt spray and soil-borne salt. Red cedars are also deer-resistant, while arborvitae are delicious to deer. Other good evergreen choices are inkberry holly (Ilex glabra), blue spruce (Picea pungens), and mugo pine (Pinus mugo).
Even leaf-losing trees can protect salt-sensitive plants from salt spray in the winter. Old favorites like lilacs (Syringa), pussy willows (Salix discolor and S. caprea), and sweet gum (Liquidambar styraciflua) slow the winds that carry the salt spray.
For a flowerbed near a roadway or walkway where soil-borne salt is likely, try these salt-tolerant perennials: tickseed (Coreopsis), blanket flower (Gaillardia), yarrow (Achillea 'Moonbeam'), candytuft (Iberis), butterfly weed (Asclepias tuberosa), and cranesbill geranium (Geranium). Also, try plantain lily (Hosta), daylily (Hemerocallis), or coral bells (Heuchera). Don't forget late-season bloomers like stonecrops (Sedum), New England asters (Symphyotrichum novae-angliae), obedient plant Physostegia virginiana (Physostegia virginiana), and Joe Pye weed (Eutrochium, formerly Eupatorium). Always tuck in some annuals among your perennials. Zinnias, moss rose (Portulaca), calendula, and petunias will provide non-stop color and tolerate salt.
Even though Pennsylvania is one of the salt-belt states, our winter deicers do not need to negatively impact our gardening. By planning well, we can be both safe in the winter and have lovely landscapes.
