“Take Two of These and Call Me in the Spring”

Written by: Anthony C. Arnoldi, ISA Board-Certified Master Arborist WI-0102B

Posted: 2024 | Fall | Fertilization | Plant Health Care

Trees have had their share of problems this year:
• Diminishing root systems due to recent alternating drought and wet conditions. Root rots have taken advantage of this weather pattern favoring their development and advance.
• Wood boring insect populations have risen to high levels due to last year’s deep drought and are attacking various tree species.
• Chlorosis (yellowing due to decreased chlorophyll levels in the leaves) has begun or intensified on susceptible trees. The very wet spring and early summer washed available iron, other  micronutrients, and even Nitrogen down and through the soil profile, away from roots, initiating deficiencies in trees. Such trees make less food and dieback starts from starvation.
• Needle and shoot diseases of evergreens and fungal leaf spot diseases of deciduous trees are visible everywhere, wet spring weather having promoted infection.
• Storm damage in many areas.
• Dieback and decline have started on many trees because of these problems.

Combinations of these various issues have left our trees stressed, vulnerable to further insect and disease attack, and in less-than-ready condition to endure another long winter.

One of the most powerful tools arborists have at their disposal to help trees recover from stress and damage is fertilization. It is often necessary to help trees by controlling insect or disease attacks, but when it comes to actually improving the health and vigor of trees, fertilization is the cornerstone. Several options of fall fertilizer formulation enhance our ability to help your trees recover and avoid potential problems:

• Polymer-based nitrogen in a specially balanced complete fertilizer allows us control in dosing correctly and completely for an entire year without “pushing” the tree or stimulating excessive
growth. This provides the necessary elements for growth, defense, replacement leaves or roots, and compensating for physical and environmental stresses.
• Root biostimulants and humates. This enables the roots to be primarily targeted to compensate drought, construction damage, and root rot damage. It is invaluable in assisting trees without
stimulating key root rot, vascular, fungal shoot blight or other diseases. It can also help to avoid attack by specific insects by avoiding nitrogen. It is indispensable in encouraging newly planted trees to become established, especially in our difficult, heavy, clay-based soils.
• Soil-injected systemic fungicide will help reduce root rot activity so replacement roots can be generated.
• Soil-injected iron, or manganese (depending on tree species) can help mitigate or prevent chlorosis caused by a soil deficiency.

Your ISA Certified Arborist is best qualified to choose the right options and combinations to design the program tailored for your specific situation, and to direct changes in the program as needed to maintain optimum tree health.

Fall is the perfect time to fertilize because roots naturally peak in growth as leaves shut down for the year. Fall fertilization can enhance this peak and promote greater pickup of soil-injected materials, helping to prepare your tree for a long winter and to “wake up” in the spring!

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