Article by Sam Waggener, City of Lone Tree Forester
In urban areas such as Lone Tree, there are limited areas for trees to grow. The soil is often compacted as well as low in organic matter. With the small amount of space, compacted soils, lack of soil, air pollution, pests and diseases, competition for resources and pavement, trees have quite a challenge. One more challenge to add to the list is salt damage, the amount of pavement, concrete, asphalt and other hard surfaces make it difficult for trees to survive due to the use of salts on all of these surfaces. Salts such as magnesium chloride and sodium chloride can wreak havoc on a plants vascular tissue, often to only be seen months later.
Seeing a lot of snow in 2023
This winter in Lone Tree has been somewhat unusual regarding snow and the prolong period it has lingered around. This is due to the low angle of the sun during this time of year casting shadows as well as an extended period of low temperatures. Since December 14, 2022, and today the City has had over 25 days of below average temperatures. With these longer periods of snow and ice loitering around, one might want to use some salt to ease the cold grip of rime in the area. But for your trees and landscaping health you may want to think again.
The Impacts of Salt
The nation uses around 15 million tons of de-icer per year on roads, driveways, and sidewalks. All that salt either is blown onto nearby soil and vegetation or dissolves and infiltrates into the soil. Plants then uptake the solvent through the roots and inhibits the plants vascular system to work properly. Depending on the species of tree, some are tolerant of salt, but most trees are susceptible to water loss, nutrient loss, reduced vigor, and soil damage. Sometimes you can see this on the leaves later in the year turning yellow, premature autumn leaf coloration, twig dieback or the bottom of evergreens will have lost all needles where snow is piled.
Trees with discoloration and dead limbs/leaves due to salt.
For property owners and individuals responsible for keeping streets and sidewalks free from snow and ice, there are many ways to combat the effects of salt on trees and landscaping. The most efficient way to do this is clearing snow after the storm has stopped or clearing snow before it has become compacted down by either vehicles or pedestrians.
Salt damage is most likely to occur near roads and sidewalks where salt is frequently applied. Most Public Works crews are out before, during, and after the storm to ensure public safety on the roads. All the snow that is cleared by crews from the streets will have some salt content contained in it, and all this snow should be piled away from trees and landscaping.
To prevent salt damage to trees it is important to use salt sparingly as well as use types of salt that are less harmful to the environment. Mag Chloride is less harmful than sodium chloride, but it still can have detrimental effects.
Best Practices – Protecting Your Soil and Vegetation
The best management practices are to install trees that are salt tolerant in locations where salt is being utilized. In the spring, flush soils of all that sodium before foliage starts to bud and leaf out. Usually spring rains can do this but in high value landscaping it may be done by arborists applying excessive irrigation. This process is known as leaching, and it is the application of additional water, more than what is required for growth. After application the excess water uptakes salt particles and flushes them away from the root zone. This additional water should be removed by means of a subsurface drainage system. Another way to desalinate soils is to apply gypsum, the calcium in the gypsum replaces the sodium and the excess sodium is leached from the rootzone by water. As with salt applications, gypsum applications should be used sparingly and always read the label.
Here is a list of tree species that are tolerant of salt:
- Hedge Maple
- Norway Maple
- Silver Maple
- Hawthorns
- Ginkgo
- Honey Locust
- Junipers
- Goldenraintree
- Mulberry
- Blue Spruce
- White Oak
- English Oak
- Red Oak
- Kentucky Coffee tree
If you have questions about tree care, please contact Sam Waggener, City of Lone Tree Forester.