Winter in Wisconsin offers plenty of opportunities for outdoor enjoyment! Skiing, sledding, ice skating and more keep us active outside for the winter season. Not to mention we have holidays to look forward to in winter and plenty of family time! With so much excitement, it is easy to forget about your landscape. What is going on under all of that snow, anyways? Well, one major consideration for your landscape is deicing chemicals, especially “rock salt” or sodium chloride.
Sidewalk and street salt, while necessary to keep driving conditions safe, can be detrimental to some of our common ornamental landscape plants, not to mention our cars, our pets and even the paving surface itself. It is always a good idea to minimize the amount of personal sidewalk or driveway salt used to protect your pets, vehicles, plants and property. If possible, use sand or calcium chloride products rather than sodium or magnesium products to reduce damage. Even when we minimize the amount of winter salt we use personally, we still need to consider salt from public streets.
In regards to landscape plants, there are two types of salt damage to be concerned with – aerial salt and soil salt. Soil salt levels can be very high in areas adjacent to streets, walkways or driveways, especially where plowed or shoveled snow is dumped. Aerial salt can be an issue near highways or heavy traffic streets, where salt spray is evident.
If you have noticed any of these signs, you may be noticing the symptoms of salt damage:
Signs of Salt Damage
- Bud and twig dieback
- “Witches Brooms” or unsightly clusters of twigs sprouting from one location
- Late or poor bloom/leaf out in Spring
- Small or off-colored leaves
- Brown leaf margins
- Signs of damage most evident on side of plant facing street or source of salt spray
- Plants “dry out” more easily
- Nutrient deficiencies in soil, especially magnesium and potassium
- Off-colored, often yellow leaves
- Stunted growth
- Brown leaf margins
- Potential plant death, especially in turf or smaller perennials
Once you have identified a problem with soil or aerial salt, there are a few things you can do to minimize the negative effects.
If you notice problems due to high salt levels in soil, it is beneficial to minimize the amount of sodium chloride exposure in those areas. Try using calcium chloride, or if you must use sodium chloride, mix a small amount with sand. If you need to replace plants in those areas, choose plants that have demonstrated a higher level of tolerance to soil salt. A few good options in our area are shrub roses, daylilies, hostas, some ornamental grasses such as Karl Foerster Reed Grass and junipers.
Problems with aerial salt spray are often more difficult to prevent. Try to plan accordingly and use salt tolerant plants in areas that are exposed to heavy salt spray. In some cases, burlap can be used in winter to create a barrier to protect plants. If you choose to use burlap for this purpose, be sure to maintain an air gap between the burlap and the plant. If the burlap becomes saturated with salt spray and is in contact with the plant, damage can still occur. A fence or salt-tolerant hedge near the source of the salt spray can sometimes help to reduce damage to plants in the rest of your yard. Upright Juniper and Ponderosa Pine are two good options for this. Salt spray can travel quite a distance into the air and away from its source, especially from higher speed roadways. Choose salt tolerant trees if you live near a highway or high speed traffic. Honeylocust, Cockspur Hawthorn, and Japanese Tree Lilacs are among the trees most tolerant of salt spray in our area.
To simplify a complex issue, remember that salt water makes us thirsty, and it makes our plants thirsty too! High levels of salt in the soil, or directly contacting your plants can absorb water that would otherwise be used by your plants. Your plants will very likely have to deal with some salt issues each winter, but by following these tips you can minimize the negative effects of deicing products. Start preparing in fall by giving your plants plenty of water to prepare for winter. In spring, try not to wash slush or salt from the sidewalks into your yard or planting beds. Enjoy your winter wonderland and healthy plants next spring by using salt products responsibly and following these landscaping tips!