There are many factors that affect the health and appearance of your tree. Some factors, such as light, water, and soil availability, are obvious and more easily assessed. However, the acidity of the soil around your tree has a huge impact on the ability of your tree to absorb the required nutrients.
In a forest the soil is slightly acidic and most trees are well equipped to succeed in these types of environmental conditions. However, the soil in Toronto is generally alkaline (7.5-8 on the pH scale). A high pH limits the ability of the tree to absorb certain nutrients such as manganese and Iron because bacteria that release many nutrients from organic matter operate most efficiently in soils that are slightly acidic (in the 5.5-7 range).
Many trees in Toronto may have a “sick” or unhealthy appearance because they cannot access nutrients that may be in the soil but are not in a useable form. If you have a Red Maple, Pin Oak, River Birch, Sweetgum, Pear, Dogwood, Pine, Spruce, Fir, or Hemlock on your property, you may notice leaves and needles that are small and discolored. They may also have a thin canopy, poor growth, and stem dieback. All of these species are considered “Alkaline Intolerant.”
Reducing the pH even slightly can have a significant effect on the appearance and health of alkaline intolerant plants. To reduce the pH on a property, Cohen and Master first takes a sample of your soil and tests it to determine the exact acidity levels. We then use a slow release sulfur product that is applied in a granular form or a citric acid product in a liquid form to the soil. Treatment methods will always depend on the specific needs of your plants. Soil pH is not easy to manipulate and your soil will always work towards reverting back to its original acidity, which is why annual application is necessary. Applying sulfur in a slow release form is extremely important to avoid leaching into water sources. This also reduces the need for frequent reapplications during the year.
The best way to avoid chronic health problems with your trees is to choose a species appropriate for the soil conditions on your property. Cohen and Master can collect a sample of your soil, test it to determine the pH level, and recommend trees to plant that are well-suited to the specific conditions on your property.
By: Rachael Kowaleski, BES
Consulting Arborist, Cohen & Master Tree and Shrub Services