Save Your Trees From Salt Damage
By Rebecca Willison
MWC often gets questioned in the spring about why trees along roadways have brown leaves or needles and how this can be avoided. While tree damage from road salt usage doesn’t become obvious until the spring, now is the time to consider ways to minimize damage over the winter.
Approximately five million tonnes of road salt are released into the environment in Canada each year. The most commonly used road salt is the same salt that is used on food – sodium chloride.
Although road salt assists with keeping pavement dry and safe during the winter and has little negative effect on human health, its widespread use can cause damage to trees, shrubs and other plants along roadways.
How salt damages plants
Road salt can damage plants in two ways. The first is through an airborne spray that kills dormant buds by penetrating leaf scars. The second occurs when salt accumulates in the soil where it breaks down into its two components, sodium and chlorine, both of which act differently to affect the plant.
In extreme cases, chlorine ions in the soil are taken up by the tree in early spring, where they enter the sap and concentrate in shoots, preventing bud openings. Eventually, the chlorine is transported to actively growing leaf margins where it causes leaf scorch, curling and death.
Sodium ions in the soil follow the same route as the tree’s nutrients, blocking magnesium and potassium, both of which are necessary for the production of chlorophyll. Again, in extreme cases, this can result in a potassium deficiency that may inhibit the tree’s resistance to drought and disease.
Salt accumulation in the soil can also cause a physiological drought. Salt solution near tree roots is more concentrated than the tree’s sap, impeding osmosis and preventing the tree from taking up water through its roots.
In general, the primary long-term damage to salt-weakened plants is a result of their increased susceptibility to insects, pathogens, and the environmental stress of drought, wind and ice. Tree death from road salt is less common.
Symptoms of salt damage
Salt damage to conifers is most noticeable in the spring. Branches closest to the road get yellow and brown needles that drop off. This colour change starts at the tips of the needles and progresses to affect the whole needle.
In Muskoka, the browning of trees is often noticeable on the east side of Highway 11 during early spring. By summer, these trees have usually recovered and have new green growth. Damage due to salt spray is usually short-term, with long-term damage occurring where the tree is under other stress.
Deciduous trees damaged from road salt may have many twigs densely clustered together, called witches’ brooms, near the ends of branches as a result of terminal buds killed by salt spray. Other symptoms include unopened flower buds, twig dieback, sparse, stunted or yellow foliage, and leaf scorch.
Young trees are more susceptible to salt damage because they have fewer roots than older ones.
Preventing salt damage to your trees
There are several ways that you can reduce the damaging effects of salt on your trees.
- Avoid the use of de-icing salts. Use coarse sand to help make driveways and sidewalks less slippery. If salt must be used, use as little as possible, lower the throwing distance, and apply before the area freezes.
- Keep your trees and shrubs healthy. A healthy plant is better equipped to survive salt spray and accumulation in the soil.
- Plant salt-tolerant trees near roadways and walkways. Some salt-tolerant native species include Red pine, Red oak, ashes, birches and poplars. Salt-intolerant species, such as White pine, Sugar maple, Eastern hemlock, basswood, and spruce, should not be planted near areas where salt is used.
- Use barriers to protect sensitive species from salt damage. Barriers may include plastic fencing, snow fencing, or burlap.
- Improve the drainage around trees or adjust the grade so salt is easily leached away from the trees.
- Flush the soil with water in the spring when it thaws so salts are sent beyond the trees’ root zones.
Until a cost-effective alternative to the use of conventional road salts is developed to keep our roads safe in the winter, reducing the amount of salt applied and minimizing salt damage to our trees and our watersheds is the best course of action.
Composting with Worms
Are you looking for an alternative to trudging through the snow to the compost bin this winter? Then vermicomposting is for you!
Vermicomposting is the process of using worms and microorganisms to turn kitchen waste into a black, earthy-smelling, nutrient-rich soil conditioner. Vermicomposting returns badly needed organic matter to your soil while cutting down on garbage going into your landfill.
Vermicomposting can be done indoors or out, allowing for year-round composting. It is ideal for anyone who may not have regular access to an outdoor composter, such as apartment dwellers.
Vermicompost is made in a bin filled with moistened bedding and Red worms. Food waste is added to the bin for a period of time, and the worms and microorganisms eventually convert the contents of the bin into a compost called “castings.”
The Red worm
The best type of worm to use for vermicomposting is the Red worm, Eisenia foetida. Red worms are incredible garbage eaters that eat and expel their own weight everyday.
Red worms can be obtained from vermicomposting suppliers, bait shops, or friends and neighbours already actively vermicomposting.
Plastic storage containers with tight-fitting lids make good worm bins. Another option is to build a bin out of wood. To provide the necessary darkness for your worms, make sure your bin is opaque.
The size of your bin will depend on the amount of food waste generated each week and the number of people generating the waste. In general, provide one square foot of surface area for every pound of food waste generated each week. See the chart below for guideline dimensions.
|Number of People||Quantity of Worms||Bin Size (h x l x w)|
|1 or 2||1 lb.||1.5’ x 2’ x 1’|
|2 or 3||2 lbs.||2’ x 2’ x 1’|
|4 to 6||3 to 4 lbs.||2’ x 3.5’ x 1’|
Drill 8 to 10 holes in the bottom of your bin for drainage. Duct tape some fine screening over the holes to stop worms and bedding from falling through. Keep your bin raised with a tray underneath to catch excess liquid that can be used as a plant fertilizer.
Your bin needs a lid to keep in moisture and provide darkness for your worms. Drill several small holes in the lid for ventilation.
Vermicomposting bins can be used indoors all year round and outdoors during the milder months. If you place your bin outdoors, keep it out of the hot sun and heavy rains.
If the temperature drops below 4˚C, move you bin indoors or insulate it against the cold.
Red worms can survive in many types of bedding material. The bedding material you choose must be able to retain both moisture and air while providing a place for your worms to live. Your worms will eat their bedding, turning it into castings.
Common bedding materials include: shredded newspaper, straw, peat moss, shredded cardboard, grass clippings, dried leaves, or a mixture of these materials. Initially, the bedding should fill two thirds of your bin.
It is very important to keep the bedding as moist as a wrung-out sponge. If the bedding begins to dry out, use a fine mist to dampen the bedding again.
When putting in new bedding, fluff it up to create air spaces to help control odours and allow free movement for the worms. Add a couple of handfuls of sand or soil to provide the grit needed by the worms to digest their food.
To add worms to your new bin, simply scatter them on top of the bedding and watch them burrow in to get away from the light.
Feeding your worms
Red worms will eat almost any type of food wastes. Feed them fruit and vegetable scraps, coffee grinds, tea bags, and finely crushed egg shells.
To reduce odours and pest problems, avoid feeding your worms starches, meats and fats.
With a new bin, start slowly until your worms build up their population and can handle larger amounts of food.
Feed your worms once or twice a week by burying your food scraps at least one inch below the surface of the bedding. To speed up the composting process, chop up your food scraps into small pieces. Place the food in a different section of the bin each week.
After about three months, you will start to notice that your worms have converted food wastes and bedding into a mass of rich, dark castings. When the volume of their bedding has decreased and you can identify individual castings, it is time to harvest the compost.
To harvest, take the lid off of your bin and expose the contents to bright light. This will cause your worms to work their way towards the bottom of the bin and allow you to remove the castings a layer at a time.
Most of the worms will be left in a shallow layer of castings at the bottom of the bin. It is time to add new bedding and start all over again.
Using your compost
Compared to ordinary soil, castings have five times more nitrogen, seven times more phosphorus, and eleven times more potassium. The castings you harvest from your bin will provide nutrients for your plants and will help the soil retain moisture.
This compost can be mixed with potting soil and used for houseplants, as mulch for potted plants, or sprinkled on your lawn as a conditioner. In the garden, simply work the compost into the ground around the base of each plant.
For more information on starting and maintaining a vermicompost system, refer to Mary Appelhof’s book “Worms Eat My Garbage” (Flower Press, 1982).