Soil Health Management
In a natural forest setting, trees take care of themselves. Each fall the soil is covered with leaves providing an ample supply of mulch and eventual organics and nutrients. Urban soils are often compacted, lack organics, and have restricted space for tree roots to grow. Many tree health concerns start with the area below ground that we cannot see.
Feelings on the importance of healthy soils from The BIG Oak = Trees and lawns did not evolve together, will not thrive together, but they can exist together. Soil health equals tree health.
The Benefits of Mulching
Insulates the soil microclimate from colder winter temperatures and warmer summer temperatures
Keeps mowers and weed trimmers away from the trunk
Reduces amount of lawn area and eliminates competition from turf
Breaks down into organics over time
Helps suppress weeds
Creates a more natural environment in unnatural urban landscapes
Stimulates growth; mulched plants grow faster that non-mulched plants.
A note from The BIG Oak = The biggest mistake people make is thinking more is better. Creating a “mulch volcano” around the trunk is not an appropriate method of mulching. Keep the volcanoes in Hawaii. Mahalo. Apply mulch WIDE, not deep.
Stem Girdling Roots
Stem girdling roots (SGR’s) encircle the trunk just above or below ground causing compression of the trunk. This pressure can lead to tree stress, dieback, failure at ground level and eventually tree death. SGR’s are commonly found on existing trees that exhibit no visible root flare or were planted too deep. Trees with SGR’s may show the following symptoms:
Leaf scorch
Dieback of stems and branches
Reduced growth and thinning overall crown
Early fall color
Heavy seed production
Planting Depth
Trees that are planted too deep will have a difficult time establishing and thriving. Trees that are planted too deep can lead to the following:
Reduction in leaf size and growth rate
More susceptible to insect and disease attack
Reduction in cold hardiness
Increased stress from drought conditions
Development stem girdling roots
Shortened life span
A MAJOR lesson from The BIG Oak = Planting trees too deep can be considered a TOP 5 tree killer. After 27 years in the tree industry, I have removed far more trees from planting depth issues than Dutch elm disease, oak wilt and Emerald ash borer combined.
Soil Compaction
Soil compaction can have a devastating impact on tree health. When soil is compacted, soil oxygen (which is critical to tree health) is removed making it difficult for roots to grow and survive. Soil compaction can also change water infiltration patterns and soil structure. The best way to combat soil compaction is prevention.
Symptoms of soil compaction often show up 2-5 years after the actual damage. Symptoms may include small leaf size, stunted growth, thinning crown, dying crown, tip dieback or even death.
It is vital to protect the Critical Root Zone of a tree when construction or other activities occur. For every 1 inch of tree diameter, 1.5 feet (radius) of root zone must be protected. For example, a 20-inch oak tree must have 30 feet of roots protected in every direction (sorry for the math).
Nutrient Deficiency
When a tree has a nutrient deficiency, it does not always mean that the soil is lacking the nutrients. In soils with high pH, some trees species cannot gain access to nutrients such as iron and manganese. Chlorosis (iron deficiency) is common with river birch and pin oak. Manganese deficiency is common with red maple. These deficiencies can lead to stress, dieback and eventually tree death is severe cases.
Proper Watering
Improper watering is the number one reason that new trees do not survive their first year. Proper watering is the key to the establishment of new plantings. The time it takes a tree to establish is directly related to the size of the tree. Newly planted trees that are larger will take a longer time to establish a healthy rooting system.
How Much Water?
Many factors impact how much watering will be required to help a tree establish. These factors include tree type, temperature, humidity, wind, soil type, and soil conditions. Soils should be kept consistently moist but not saturated. Trees in sandy soils will require more watering than trees in clay soils. Over watering (specifically in clay soils) can be just as damaging as under watering.
Leaf Scorch
Leaf scorch is a physiological problem related to watering. The leaves lose water at a faster rate than can be replaced by the tree. Leaf scorch can be caused by anything that can interfere with the uptake of water. Leaf scorch is not a disease and is often caused by a variety of issues.
What causes Leaf Scorch?
Environmental conditions that increase the water demands on trees include hot temperatures, low humidity, high light intensity, and high winds. Strangely enough, leaf scorch can also be caused by excessive water in the soil. Saturated soils do not allow roots to get access to oxygen. As roots suffocate they start to die and the tree cannot take up water as the leaves are dying out. This situation is most common in heavy clay soils.
