Common Nutrient Deficiencies & Toxicities and Their Symptoms in Trees

Abiotic Disorders
Written By Chris Welch

In my preparation for the BCMA exam, I've deepened my focus on the crucial aspect of nutrient management in trees. Though I had a foundational understanding, honing in on nutrient deficiencies and toxicities has significantly expanded my understanding. Trees require a balanced nutrient profile for optimal physiological function, and imbalances can manifest through various symptoms. It goes beyond mere problem identification; it's about understanding the nutritional needs for the biological health of trees. Here, I'll delve into common nutrient imbalances in trees and their symptoms.

Common Nutrient Deficiencies in Trees

  1. Nitrogen Deficiency:

    1. Symptoms: Older leaves turn yellow (chlorosis), stunted growth, and poor leaf production.

    2. Affected Parts: Older leaves are typically affected first.

  2. Phosphorus Deficiency:

    1. Symptoms: Purplish discoloration on leaves, reduced growth, and weak root systems. Leaf drop and delayed maturity may also occur.

    2. Affected Parts: Symptoms can initially appear on older leaves due to the mobility of phosphorus, but they can also manifest on younger leaves, depending on the severity of the deficiency.

  3. Potassium Deficiency:

    1. Symptoms: Leaf scorch or browning at the edges, yellowing between leaf veins, and weak stems and roots.

    2. Affected Parts: Older leaves show symptoms before younger ones.

  4. Calcium Deficiency:

    1. Symptoms: New leaves are distorted or irregularly shaped, and root tips may die back.

    2. Affected Parts: Symptoms usually show on new growth.

  5. Magnesium Deficiency:

    1. Symptoms: Yellowing or bronzing of leaves starting between veins, leaf curling, and twig dieback.

    2. Affected Parts: Older leaves are affected first.

  6. Iron Deficiency:

    1. Symptoms: Yellowing of leaves (interveinal chlorosis) while the veins remain green, leading to extremely pale leaves.

    2. Affected Parts: Newer growth is usually more affected.

  7. Manganese Deficiency:

    1. Symptoms: Interveinal chlorosis, often starting with the youngest leaves; advanced deficiency can lead to necrotic spots and leaf drop.

    2. Affected Parts: Young leaves are typically more affected. However, in severe cases, symptoms can extend to older leaves as manganese is relatively immobile in plants.

Common Nutrient Toxicities in Trees

  1. Nitrogen Toxicity:

    1. Symptoms: Excessive leaf growth at the expense of flower and fruit production, dark green leaves, and susceptibility to pests and diseases.

    2. Affected Parts: Usually appears on the whole plant.

  2. Phosphorus Toxicity:

    1. Symptoms: Though rare, excessive phosphorus can lead to imbalances in micronutrients, causing symptoms like chlorosis due to iron and zinc deficiencies.

    2. Affected Parts: Symptoms may appear across the plant but are more likely to be observed in new growth due to the inhibition of iron and zinc uptake.

  3. Potassium Toxicity:

    1. Symptoms: Excess potassium can lead to deficiencies of other nutrients like magnesium and calcium, resulting in their respective deficiency symptoms such as leaf chlorosis and weak growth.

    2. Affected Parts: The symptoms can vary widely, often depending on the nature and severity of the secondary deficiencies caused by the potassium imbalance.

  4. Calcium Toxicity:

    1. Symptoms: Stunted growth, diminished root development, and potential interference with the uptake of other nutrients.

    2. Affected Parts: Generally affects the whole plant.

  5. Magnesium Toxicity:

    1. Symptoms: Rare but can include leaf scorch, wilting, and interveinal chlorosis.

    2. Affected Parts: Typically affects older leaves first.

  6. Iron Toxicity:

    1. Symptoms: Bronzing and stippling of leaves, leaf loss, and root damage in severe cases.

    2. Affected Parts: Usually affects new growth.

  7. Manganese Toxicity:

    1. Symptoms: Dark specks or streaks on older leaves, leaf distortion, and necrotic brown spots.

    2. Affected Parts: Older leaves are more commonly affected.

Key Factors

Determining whether a tree is expressing a nutrient deficiency or toxicity involves several key factors:

  • Symptom Analysis: Carefully observe the symptoms (such as leaf discoloration, stunted growth, and leaf drop) and their progression. For instance, deficiencies often start on older leaves, while toxicities can affect the whole plant.

  • Plant Part Affected: Identifying which parts of the tree are showing symptoms. Deficiencies and toxicities can affect different parts of the tree in distinct ways.

  • Soil Testing: Conducting soil tests to check nutrient levels. High nutrient levels indicate toxicity, while low levels suggest a deficiency.

  • Tree Species: Some species are more susceptible to certain nutrient imbalances than others. Knowing the specific requirements and common issues of the tree species is crucial.

  • Environmental Factors: Considering ecological conditions such as pH, moisture, and temperature, they can influence nutrient availability and uptake.

  • Fertilization History: Reviewing the tree's fertilization history can provide insights into potential causes of nutrient imbalances.

  • Overall Tree Health and Context: Assessing the tree's health and other stress factors (like pest infestations or mechanical damage) that might compound or mimic nutrient-related issues.

Combining these factors helps accurately diagnose whether a tree is suffering from a nutrient deficiency or toxicity and determine the appropriate action.

Additional Reading

University of Maryland Extension:

Michigan State University Extension:

Royal Horticultural Society (RHS):

Strock, C.F. (2020, October 26). Plant Nutrient Deficiency Symptoms (Nitrogen, Phosphorus, Potassium) [Video]. YouTube. https://youtu.be/ZSNuMOxYReM?si=ZjRv7jmkcKWXWFHE

Chris Welch
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