[Last update: November 2025]

Quick Links to Topics Covered in This Article:

INTRODUCTION  •  Dessication Stress Death: “Sudden Death”
Water is the Best Medicine  •  Be Proactive
Should I Fertilize My Trees?  •  Unseasonal Heat Trends

INTRODUCTION

HEAT & DROUGHT STRESS can negatively impact your landscape plants, particularly your trees. The photo below is from an actual irrigated lawn following several heatwaves. Despite receiving water from an irrigation system, the greenest areas of the lawn were those that were “protected” from sun exposure by shade trees most of the day. The rest of the lawn, on the other hand, was drying out. For many homeowners, a “weed-free” green lawn is a priority. They will invest in an in-ground irrigation system with the primary goal of their lawn’s success (and their trees only as an afterthought). Perhaps, they reason that ‘trees are big enough plants and can take care of themselves!‘ Unfortunately, when it comes to their existence in our urban settings, that is furthest from the truth!

If you have an irrigation system and your lawn looks like this…

Just think about how much your trees are suffering!

Did you know that turfgrass, with or without an irrigation system, can survive a period of prolonged high heat and drought by going into dormancy? Many types of turfgrass can do this with little residual side effects other than a browned appearance, thinning, and yielding space to more tolerant weeds. Once climate conditions become more moderate with sufficient water, turfgrass will be restored and produce green shoots once more.

For additional information on recommended grasses for Midwest Lawns and drought recovery, see:

• Low Maintenance Lawns in the Midwest (Michigan State University Extension)
• Purchase Quality Grass Seed For Your Lawn (Purdue Extension & University of Illinois Extension)
• Dealing with Drought (Purdue Extension)

On the other hand, the same restorative response does NOT hold true with trees!

The Red Maple (Acer rubrum) below died in 2017 following 2016’s severe drought conditions. As you can see, the plants surrounding the maple appear healthy, and it itself has produced foliage during the current season. Sadly, despite being in an irrigated area, it did not survive long into the season when the summer’s heat got the better of it. (Note: It had grown successfully for years along with other maples in a business park, but it was the only tree in the row of maples that did not survive. Girdling roots (which restricted some of its ability to transport sufficient amounts of water from its roots) contributed significantly to its rapid decline.)

Although harsh conditions will indeed initiate a “shutdown” process, such as the closing of leaf stomata (to prevent water vapors from escaping, thus reducing moisture loss), leaf abscission (leaf drop), cladoptosis (shedding off of limbs), and reduction of root biomass, the hydration needs of trees are nonetheless far more complex than turfgrass. The volume of water needed to sustain trees plays a critical part in their survival. The longer a tree must endure high heat and drought without proper hydration, the more residual damage will occur to its biological system.

And so, even if certain plants appear to have escaped the “Grim Reaper” this year, this does not mean they weren’t affected by the harsh climate conditions. Decline and even death in some trees can occur either suddenly, slowly, or on a “biological” delay. Symptoms of decline, such as stunted growth and dieback, may not become noticeable until the following year, and symptoms may increase over the next several years.

DESSICATION STRESS DEATH: “SUDDEN DEATH“

“Sudden death” is a term we use to describe the situation of a tree that looks fine one day and then suddenly dies (within hours, days, or a few short weeks) following a significant thermal climate event, such as a heatwave, and is characterized by wilted & browned leaves that are still firmly attached to their twigs. This phenomenon is sometimes referred to as Dessication Stress Death. This rapid dehydration causes cell damage and death that outpaces the normal process of leaf abscission, leading to leaves remaining attached while the plant dies. This is distinct from typical seasonal senescence, which is a more gradual, hormonally regulated process of aging and nutrient recovery before leaf drop.

It is also not uncommon for a tree planted among its own species to seemingly die at random and for no apparent reason. This scenario is known as Differential Mortality and may occur even when all conditions seem to be the same. The underlying cause is that some trees are simply less resilient to stress than their neighbors. A single tree can succumb to multiple interacting factors that eventually overwhelm it, while its stronger neighbors endure. This process is sometimes referred to as the Dieback-Decline Complex, as trees undergo a gradual decline in vigor before dying. Insufficient water, poor root establishment, girdling roots, and improper transplanting, which may be exacerbated by a localized drought, poor drainage, or nutrient deficiency, secondary organisms (e.g., pests and diseases), genetic variability, etc., are leading contributors to sudden death.

The weaker or sicker an unmanaged tree is, the more likely it will succumb to heat & drought stress. As mentioned earlier, trees with girdling roots will have a very tough time keeping up with their hydration needs because the girdling is literally strangulating the lower trunk stem above, at, or below the root crown (a.k.a. trunk flare, root flare), restricting the flow of nutrients and life-saving waters drawn from the root system. (See “Girdling Roots – The Silent Tree Killer”)

WATER IS THE BEST MEDICINE

In the Indianapolis (Indiana) area, 2018’s unseasonably hot climate began early in the spring and has become a recurrent theme ever since (as of 2025). Many Hoosiers have joked that we never had a spring this year, but jumped straight from winter into summer! Lindsey Purcell, the Urban Forest Specialist at Purdue University in West Lafayette, IN, humorously coined the phrase “Sprinter” to describe how winter melded almost seamlessly into spring and went straight into summer! A few years ago, Lindsey wrote an excellent publication on the subject of drought. which we highly recommend you download, read, and keep handy. The PDF of this publication is available here: “Drought? Don’t Forget the Trees!”

The repetitive heatwaves have pushed even healthy plants to their limits! Ornamental landscape plants with even the slightest ailments are having even more difficulty coping with the heat! You may have noticed that some trees have already lost many of their leaves. Some of these trees may have nonlethal diseases, such as Apple Scab on Flowering Crabapples (see photo below), Powdery Mildew on Sycamores, Anthracnose on Ash trees, Tubakia Leaf Spot on Oaks, etc.) or insect feeding injuries caused by Japanese Beetles on Lindens, Eastern Tent Caterpillars on Crabapples, Aphids on River Birches, White Pine Weevils on Conifers, etc. These plant health problems (along with many others) combined with the unseasonably high heat, can make ailing trees appear extra “ugly” due to increased defoliation. Diseased and insect-damaged leaves tend to dry out quickly, turn “extra-crispy” and drop earlier than normal throughout the spring and summer seasons. This was especially true for Indianapolis trees when temperatures lingered above 85°F into the 90s over several days. Not too surprisingly, many ill trees died.

Apple Scab (Venturia inaequalis) is a fungal leaf spot disease (see circle inset) that causes premature leaf abscission in Malus spp. trees. Leaf loss is more profound and severe when it is exposed to prolonged periods of intense heat and drought conditions. Eventually, the crabapple succumbs and dies (square inset) because its roots were also “bound” from improper planting years ago.

Watering according to a plant’s needs, however, is still the best medicine. You don’t have to water every day, but if you do water, please make sure it’s a good, deep soak to encourage deeper growing roots. Shallow watering usually only encourages shallow, less drought-tolerant roots, and so during periods of high heat and drought, shallow roots are the first to dry up and may eventually die. What is your contingency plan? Don’t wait until the heat is upon you. Have a plan in place and ready. Your trees are counting on you! (See our article “Watering Trees – How Much?“)

BE PROACTIVE

How can you protect your landscape from heat and drought? Well, aside from transplanting your trees properly and ensuring they get enough water, another way is to simply pay close attention to drought trends. Keep updated on the latest weather reports and forecasts, and, if you’re really ambitious, look up historical weather data to draw timeline comparisons. It’s nearly impossible to predict the weather with 100% accuracy (because sometimes relying on weather forecasts can be a game of roulette), but by combining resources, you’ll discover clues that can prepare you to manage the needs of your plants so that they receive adequate supplies of life-sustaining water during the hot & dry seasons.

To check soil moisture, use a screwdriver (over 8″ long) to poke into the soil. If the soil is moist, it should pass easily through it, but if the soil is too dry and you can’t push the screwdriver into it at least 6″ deep, then it may be time to water (or maybe, you have some very rocky soil!). A handy tool to have is a Soil Moisture Meter (SMM). A SMM is a probing device that you insert about 4-6 or more inches into the soil. Its display will give you a general idea of whether your soil ranges from dry to moist to wet. Examples of simple SMM can be found on Amazon’s website.*

SHOULD I FERTILIZE MY TREES?

Performing some plant health care (PHC) treatments in temperatures above 85°F may put a plant at greater risk of phototoxicity, “leaf burn” from phototoxicity, and additional plant stress from phototoxicity. Poor timing, choice of chemicals, application method, and rates used are some of the main factors that may influence a less-than-desirable result. PHC treatments might include applying fertilizers (usually to address nutrient deficiencies) during high temperatures, managing diseases & controlling insect infestations late after infection/infestation has already caused significant plant injury, etc. In the case of fertilizers applied to an already stressed plant, there is a risk that these plants could run out of energy while trying to metabolize the nutrients fed to them. Additionally, these mineral “salts” can cause a drying effect (a.k.a. reverse osmosis) and deprive the plant of vital moisture. So use caution because applying supplemental fertilizers on stressed trees may do far more harm than good! It is imperative as a best management practice to read product labels in their entirety and to follow their directions exactly to minimize plant injuries, to maximize results, and in certain cases, to stay in compliance with the Law. (Related articles: “Leaf Scorch” and “Why Does Over-Fertilization Kill Plants?”)

*Please Note: SMMs are not 100% accurate, and can vary in quality and features depending on their manufacturer. These still can be useful devices in indicating watering needs. The mention of trade names or commercial products in this article is solely for the purpose of providing subject matter-related examples and does not represent, imply, or constitute an endorsement of one brand over another. Arbor Rangers, LLC, or its associates, do not warrant, nor guarantee results by use of any specific name-brand product in addressing your specific needs. This article may contain pesticide, equipment, and/or product type recommendations that are subject to change at any time. The recommendations are provided only as a guide.

The following chart shows the unseasonably high temperatures that popped up and lingered near the end of spring and into summer in the Indianapolis area from May 15, 2018 – July 19. 2018. Included for comparison are historical averages from the National Weather Service and high temperatures recorded from 2017.

2018 OVERVIEW OF UNSEASONABLE HEAT TRENDS (Indianapolis, IN) May 15 – July 19

As you will see from the chart below, this year Indianapolis has experienced unseasonably HOT temperatures (highlighted in yellow) and very little precipitation (highlighted in blue). Compared to last year’s temperatures, which started out unseasonably high but then registered closer to the historical averages (notable exceptions highlighted in orange), this year will definitely have a tremendous (and devastating) effect on landscape plants over the next few years.

Of the many ways to kill a tree in the landscape, Girdling Roots ranks high among them, along with poor irrigation, planting too deep (which often causes girdling roots), and mechanical injuries. But just what are girdling roots and where do they come from? [Note: Most photos and images have an enlarged view if you click on them.]

SUFFOCATION – Girdling roots can result from roots that develop as a response when oxygen availability has been reduced below necessary levels. This can happen when a plant has been planted too deeply, or by the addition of too much top soil (i.e. grade change) or from improper mulching (i.e. too deep; “volcanic” mulching), or soil compaction, etc.

CONTAINMENT – Girdling roots are common with container-grown plants. If they remain in the container too long their roots will be deflected by the container walls, causing them to grow in a circular pattern. Even a ball & burlap tree can develop girdling roots if left in this packaging for too long. Another type of containment may be the improper use of edging materials.

Whatever the reason, girdling roots encircle or cross-over the trunk/root flare of a plant rather than radiating outward (like a bicycle’s wheel spokes). Over time the trunk and girdling roots continue to expand in diameter with each new annual growth ring. Before too long, severe compression to the lower trunk areas create tremendous pressure upon the underlying vascular system (i.e. xylem and phloem). As this constriction builds up the lower trunk stem may begin to swell.

If left unresolved, the conflicting root(s) may eventually choke and strangle the plant, interrupting the uptake of water and nutrients completely in the girdled zone, which, in turn, leads to:

• plant decline
• attracting wood-destroying organisms
• premature fall color of foliage
• defoliation
• dieback of xylem, cambium, and phloem layers
• loosening and detachment of outer bark
• dieback of twigs, branches, and stems
• high-risk severe dehydration during droughts
• and may eventually kill the entire plant.

Girdling roots are called “the silent killer” for a reason. No one appears to take notice of the deadly damage they do until it is too late… a tree declines severely and then dies. Although girdling roots can occur naturally, many times they result from improper planting and poor cultural practices. Not surprisingly, MOST of these girdling root problems in our landscapes could have been avoided if good management practices were in place.

PREVENTION and ANNUAL MAINTENANCE

The best prevention of girdling roots is to plant trees properly from the start and then annually inspect them before laying down new mulch and avoiding volcanic mulching.

If a tree has been on site for a while and has existing girdling roots, some of these may be removed using hand-pruners without causing significant harm to the tree. On the other hand, severely girdled trees usually require the skills, knowledge and an experienced of a Certified Arborist because not all girdling roots can be safely removed, nor should they be. There are instances where a tree becomes dependent on the very girdling root that is killing it because the root has matured and grown to such an extent that it actually sustains a portion of the tree with vital water and nutrients. To remove such a root would only accelerate the demise of an already doomed tree. If such a tree does not pose a risk to humans or property, it may be best to let it live out its life, serving as habitat for other creatures, until it finally falls down or becomes an eyesore that needs removal.

Here is a sequence of field photos from a typical girdling root removal job performed by Jeff Harris (2017). Click images to enlarge:

The AIR-SPADE

Although simple girdling root operations may not require much excavation to access them, most jobs are not so easy. The best method for clearing away soil to inspect for girdling roots is through the use of an air-spade (a.k.a. air-knife). Unlike using a shovel, this is a professional air excavation tool that utilizes a highly compressed jet of air to remove soil without causing any serious harm to a tree’s root system. With the soil removed, the root system is revealed and girdling roots, if present, are exposed allowing for better assessment. A trained arborist can then remove these, wherever possible, so long as the removal(s) are not detrimental to the tree or otherwise accelerate a tree’s decline. Here’s a video that features how the AirSpade works:

Here is a sequence of field photos from a typical air-spading job. The soil excavation and girdling root removal work were performed by Aaron Wimmer and Jeff Harris (2009). Click images to enlarge:

Types of Sanitizing Solutions for Disinfecting Pruning Tools & Equipment (Follow specific label directions, if applicable)

• Household Disinfectants (e.g. Lysol, etc.): full strength
• Household bleach (e.g. Clorox, etc.): up to 25% solution (e.g. 1 part bleach + 3 parts water)
• Rubbing alcohol (70% isopropyl): 50% solution (e,g, 1 part alcohol + 1 part water)
• Pine oil cleaner (e.g. Pine-Sol, etc.): 25% solution (e,g. 1 part cleaner + 3 parts water)

More Information on Girdling Roots

• A Practioner’s Guide to Stem Girdling Roots of Trees – (University of Minnesota) Impacts on Trees, Symptomology, and Prevention
• Stem Girdling Roots – The Underground Epidemic Killing Our Trees (University of Minnesota)
• Girdling Roots – (Missouri Botanical Gardens) The causal factors may be genetic or cultural. At the end of this article is a list of trees that may be more prone to stem girdling roots. Cultural practices that may cause girdling include poor growing practices or poor planting techniques.
• Stem Girdling Root Removal – (University of Florida) Roots that girdle the stem (stem girdling roots) can be removed. There are many examples of this discussed with photos in this article.

ACKNOWLEDGEMENTS

A special THANK YOU to a few industry professionals who gave me early exposure and opportunities to learn about girdling roots and those who enabled me to gain experience in using the AirSpade and insights and training in girdling root removals: Phil Ping , Mike Webster and Aaron Wimmer (Ping’s Tree Service/ISA Certified Arborists , Indianapolis, IN). Additional resources: Pam Louks (formerly IDNR/CUF Programs Coordinator), Gary R. Johnson (University of Minnesota Extension Professor), Lindsey Purcell (Purdue University, Urban Forest Specialist, formerly Indy Parks City Forester), Carrie Tauscher (IDNR/CUF Programs Coordinator), Andrew Hart (former Director of Urban Forestry, Keep Indianapolis Beautiful), Nate Faris (Director of Community Forestry KIB) and Jerome Delbridge (former Coordinator of KIB’s NeighborWoods program), Jon Xanders (Owner, Xanderbuilt Tree Care, ISA Certified Arborist), with additional Supersonic Air Knife information from Dave Leonard (Owner of Dave Leonard Tree Specialists, Versailles, KY).

“I’ve got some kind of creepy fungus all over my tree! Will it kill my tree?”

I get asked this A LOT. And so, I’ve created this post to offer a brief, but hopefully interesting discussion about the fascinating natural phenomena known as LICHENS (pronounced: “lye-kens”). More field photos below and you’ll find links to additional information near the bottom of this page.

But let’s first address the question concerning ARE LICHENS BAD FOR TREES?

The answer is “NO“

…they have not been shown to pose any significant harm to trees. Now you may breathe a sigh of relief!

Lichens are greenish, sometimes lettucy-looking, symbiotic growths made of fungi, yeast, and two types of algae. These grow as an interwoven mass appearing as a single individual which can develop into a sizeable “community” of lichens. Both the fungus and the alga provide something essential to the other for their survival but are not harmful to plants.

“But, WHY,” you may ask, “are these things growing on my tree(s)?”

Actually, they do not specifically pick on trees. Lichens can develop and grow on just about any stationary surface they can attach to, such as rocks, roofs, fence posts, gravestones, and even other lichens! And you can find lichens just about anywhere! As a matter of fact, there are an estimated 20,000 known species of lichens worldwide and come in a variety of colors, shapes, and sizes! They can grow flat or with a leafy lettuce appearance or other interesting (and sometimes gross-looking) structures. An increased amount of lichen on plants could indicate poor plant health because healthy, fast growing trees and shrubs are always shedding bark, making it difficult for lichen to attach. A season or more of severe drought, for instance, can slow a tree’s development allowing more time for lichens to form and populate.

Check out the photos of various lichen on different trees. (Note: The type of tree does not necessarily affect the type of lichens that grow on them.)

Moss is not lichens.	Lichens atop moss.

Hey! Are You “Lichen” What You See? LEARN MORE About Lichens Below!

• Lichens of North America – (Sharnoff’s photographic fieldwork) -This website grew out of the activities of Sylvia and Stephen Sharnoff, who did the photographic fieldwork for the book Lichens of North America, by Irwin M.Brodo and the Sharnoffs, published in November 2001 by Yale University Press.
• Lichen – (Encyclopædia Britannica) -Lichen, any of about 15,000 species of thallophytic plantlike organisms that consist of a symbiotic association of algae (usually green) or cyanobacteria and fungi (mostly ascomycetes and basidiomycetes). Lichens are found worldwide and occur in a variety of environmental conditions. A diverse group of organisms, they can colonize a wide range of surfaces and are frequently found on tree bark, exposed rock, and as a part of biological soil crust. Lichens have been used by humans as food and as sources of medicine and dye. They also provide two-thirds of the food supply for the caribou and reindeer that roam the far northern ranges.
• What Are Lichens? – (Live Science) – A lichen, or lichenized fungus, is actually organisms functioning as a single, stable unit. Lichens comprise a fungus living in a symbiotic relationship with an alga or cyanobacterium (or both in some instances). There are about 17,000 species of lichen worldwide.
• What Lichens Are Not – (USDA Forest Service) – Isn’t lichen that mossy stuff on rocks and trees? When people think of lichens, many of them think of them as a kind of moss. That could not be farther from the truth.
• Yeast Emerges as Hidden Third Partner in Lichen Symbiosis – (ScienceDaily) – For nearly 150 years, lichens have been the model organisms of symbiosis. Now researchers have uncovered an unexpected third partner embedded in the lichen cortex or ‘skin’ — yeast.

1. remember to do it,
2. know when & how much to do it,
3. and do it in a way that doesn’t discourage you from doing it.

• MULCHING AROUND TREES – Don’t forget that you need to check the mulch at least annually to monitor for new girdling roots, etc. (See: “Girdling Roots: The Silent Tree Killer”) Some soaker hose manufacturers may recommend removing them before winter’s freezing temperatures arrive because moisture retained in the hose may cause it to crack. Therefore, you may have to remember to reinstall the soaker hose the next spring.
• TREE TREATMENTS – If your trees are to receive (or recently received) any treatments to provide supplementary nutrients or to suppress insect pests infestations or disease infections, etc. then you need to ensure you provide them adequate water. This can help to reduce the potential for phototoxicity injury. [Note: Many pesticide labels caution applicators not to use their products when temperatures exceed 89°F (31.6°C). These also carry temperature precautions for storing chemicals.]

• “Heat & Drought Stress – Will Your Trees Survive?”
• Estimating Tree Water Requirements
• Watering Schedule example from the City of West Sacremento

[Last update: November 2025]

Quick Links to Topics Covered in This Article:

INTRODUCTION  •  17 Essential Elements
Using the Soil pH Chart  •  How a Soil Analysis Report Can Help You
How To Get Your Soil Tested

INTRODUCTION

Have you ever gone to a tree nursery and, to your glee, found what you thought to be the PERFECT tree for your home? Perhaps you saw it first in a magazine, on TV, or online, or maybe even caught it on sale at your local Walmart or Home Depot. Wherever you saw it, you impulsively purchase it for your property. In no time, you’ll have it in the ground and be taking selfies with it to brag to all your friends on social media!

After a few weeks, months, or years go by, you begin to notice it’s not looking as nice as it did when you planted it. “What happened? Why is it looking so sickly?” you wonder.

The 17 Essential Elements

Like most living organisms, a lack of any vital nutrients can have a negative health impact. Your trees are living organisms. Trees exhibit all the characteristics of life, such as growth, reproduction, responsiveness to their environment, and metabolism. They are made of cells, take in nutrients and water, and perform respiration and excretion. Therefore, KNOWING your soil can also help you to understand why existing trees may be failing in health. A soil analysis can help guide you to improve your soil management.

There are 17 essential elements for trees, based on the amounts needed, which are obtained from air, water, and soil, and are divided into macronutrients and micronutrients. Macronutrients are required in large amounts, while micronutrients, though needed in smaller quantities, are equally critical for survival and healthy growth.

• Basic Nutrients (Basic Macronutrients)
  These non-mineral elements are primarily supplied by air and water, rather than the soil.
  • Hydrogen (H): Comprises about 6% of a tree’s dry weight. Acquired from water, it is a key component of carbohydrates and other organic compounds that are essential for growth.
  • Carbon (C): Makes up about 45% of a tree’s dry weight. It is the foundation of all organic molecules and is used by trees to produce carbohydrates (a.k.a., sugars and starches) during photosynthesis.
  • Oxygen (O): Also makes up about 45% of a tree’s dry weight. It is obtained from water and carbon dioxide and is vital for cellular respiration, the process that releases energy for the plant to use.
• Macronutrients
  Trees require these six nutrients in relatively large amounts, which are supplied by the soil and often supplemented with fertilizers.
  • Nitrogen (N): Promotes strong foliage growth and green leaves because it is a key component of chlorophyll, the molecule central to photosynthesis. It is also essential for creating amino acids, nucleic acids (DNA and RNA), enzymes, and proteins. A deficiency results in yellowing (a.k.a., chlorosis) of older leaves and stunted growth.
  • Phosphorus (P): Crucial for converting sunlight into usable energy, a process vital for root growth, flowering, and seed development, phosphorus also plays a central role in the transfer and storage of energy within the plant. It helps trees recover from stress and increases their overall strength.
  • Potassium (K): Supports overall tree resilience by helping to regulate a tree’s water uptake and internal moisture levels, which improves its tolerance to drought, cold, and disease. It is also essential for activating the enzymes involved in photosynthesis and for strengthening cell walls.
  • Magnesium (Mg): As the central atom in the chlorophyll molecule, magnesium is critical for photosynthesis. It also helps regulate the transport of phosphorus and is involved in activating enzymes for carbohydrate and protein metabolism.
  • Sulfur (S): Important for synthesizing proteins, amino acids, and vitamins, sulfur is also involved in forming chlorophyll. It helps the tree resist diseases.
  • Calcium (Ca): As a key component of cell walls and membranes, calcium provides the structural integrity of the plant. It promotes root and shoot growth and improves disease resistance. It is also important for regulating the transport of nutrients.
• Micronutrients
  Trees need these eight soil-derived elements in very small, or trace, amounts. While needed in smaller quantities, these trace elements are critical for specific enzymatic functions. In excessive quantities, some can become toxic.
  • Boron (B): Important for cell wall formation, cell division, and the development of new growth, pollination, and fertilization, and also aids in the transport of sugars.
  • Chlorine (Cl): Necessary for the regulation of osmotic pressure, maintaining ionic balance, vital for photosynthesis and root growth, and also helps regulate water retention.
  • Manganese (Mn): This element activates enzymes involved in growth and photosynthesis, respiration, and nitrogen assimilation. It assists iron chlorophyll formation.
  • Iron (Fe): Necessary for producing chlorophyll, iron functions as a catalyst in energy transfer and is a component of many enzyme systems. A deficiency causes yellowing of the younger leaves (a.k.a., iron chlorosis).
  • Nickel (Ni): A component of the enzyme urease, and is necessary for nitrogen metabolism. Without it, urea can accumulate to toxic levels. Required to complete the life cycle of the tree and produce viable seeds.
  • Copper (Cu): Involved in photosynthesis, respiration, and the formation of cell walls, and also helps activate enzymes and increases disease resistance.
  • Zinc (Zn): Vital for enzyme function, protein synthesis, and hormone regulation, and is essential for plant growth and promoting root development, including the production of auxins.
  • Molybdenum (Mo): This element is essential for nitrogen metabolism and needed for the tree to utilize nitrogen effectively, helping enzymes convert nitrates into usable proteins.

What can cause nutrient deficiencies or nutrient-deficient-like symptoms in your trees? Well… it could be any number of reasons:

• • Poor quality tree stock
  • Wrong Hardiness Zone
  • Transplant shock
  • Poor root establishment
  • Planted too deeply
  • Inadequate amounts of water
  • Repetitive mechanical injuries
  • Incompatible or poor soil conditions

Let’s take a few moments to consider the last item on this list: Incompatible or poor soil conditions, by examining the Soil pH Chart that follows.

Using the SOIL pH CHART

One of the biggest challenges in establishing some trees in Indiana clay soils is high alkalinity and compaction. Soil pH is a measure of the acidity or alkalinity of the soil, measured on a logarithmic scale from 0 to 14. A pH of 7 is neutral; values below 7 indicate increasing acidity, and values above 7 indicate increasing alkalinity.

Soil pH is defined chemically as the negative logarithm of the hydrogen ion (H⁺) concentration in the soil solution. It is a critical indicator of soil health because it governs the availability of nutrients to plants and affects the activity of beneficial soil microorganisms. Acidic soils (typically found in high rainfall areas) have a higher concentration of hydrogen ions. Alkaline (basic) soils (common in arid regions) have a lower concentration of hydrogen ions and a higher concentration of hydroxyl ions (OH⁻).

Optimal Range: Most plants thrive in slightly acidic to neutral soils (pH 6.0 to 7.0), where nutrient availability is highest. During the planning phase of tree selection, an overlooked first step is getting a soil test. Become familiar with the following Soil pH Chart. The range from Acidic to Alkaline soils can influence the success or failure of your tree(s).

FUN FACT: DID YOU KNOW?

When it comes to Soil pH Charts and soil guides, many focus on a scale of 4.0 to 10.0 instead of 0 to 14. Why? Because the 4.0 – 10 range encompasses virtually all naturally occurring and agriculturally relevant soil pH values. While the theoretical pH scale in water-based solutions extends from below 0 to above 14 (depending on the concentration), natural soils generally range from an extremely acidic pH of around 3.5 to a very alkaline pH of 10.0. Additionally, soils with a pH value close to 0 or 14 are exceptionally rare in nature. Such extreme conditions would require extremely strong acids or bases, which are not found in typical soil environments. Therefore, charts for gardening and agriculture aim to present the most practical information for plant growth and soil management. Since healthy plant growth is severely limited outside the 4 to 9 range due to nutrient deficiencies or toxicities (e.g., aluminum toxicity at low pH), focusing on the 0-10 or 4-10 range is sufficient for most practical purposes. NOW YOU KNOW!

This DID YOU KNOW? is based on an online article by Guodong “David” Liu and Edward Hanlon (Publication #HS1207 (March 2024), IFAS Extension)

After a laboratory analysis, a soil test report will typically show specific soil nutrient content, soluble salts, and pH level.

NOTE: Typically, standard soil tests do not analyze for contaminants, such as bacteria, mold, fungi, herbicides, etc. Therefore, if soil contamination is a concern (say, for example, bacterial problems associated with Crown Gall disease, which affects roses, euonymus plants, willows, etc.), then more advanced analysis is needed, and that would require the help of a microbial services laboratory, which may charge a significantly higher lab processing fee.

When foliage lacks normal spring and summer coloration and displays pale or yellowish tones rather than green, it may be due to a nutrient deficiency condition known as Chlorosis.

Chlorosis is the yellowing of leaves in trees due to a lack of chlorophyll, which is caused by a deficiency in essential nutrients like iron, magnesium, or nitrogen. This impairs photosynthesis, leading to symptoms like pale green or yellowing leaves, and can progress to leaf scorching, twig dieback, and eventual tree death if untreated. The most prominent sign is leaves turning a pale green or yellow, often with darker green veins (interveinal chlorosis).

Common Nutrient Deficiencies and Contributing Factors Associated with Chlorosis:

• Iron deficiency: Typically causes interveinal chlorosis, starting on younger leaves, as the veins remain green while the tissue between them turns yellow.
• Nitrogen deficiency: Tends to cause older leaves to yellow uniformly.
• Magnesium deficiency: Often shows yellowing between the veins but may also turn the leaves bronzy-orange.
• High soil pH: Alkaline soils can make it difficult for trees to absorb iron and other nutrients, even if they are present.
• Poor soil conditions: Compacted or waterlogged soil can restrict root function and nutrient uptake.
• Root damage: Physical damage to roots from construction or disease can also cause chlorosis.

How a SOIL ANALYSIS REPORT Can Help You

• This is where the pH rating may be an important factor to note. What is the soil pH rating? Is it too low, too high, or just about right? In reference to the aforementioned Soil pH Chart, the optimal pH range for most plants on a rating scale from 0 to 14 is between 6.0 to 7.0, with 7.0 being neutral. In the example Analysis Results report below, the pH level of the soil sample submitted is 7.3 (circled in red) and considered high.
• The soil texture (or percentage of sand, silt, or clay) determines how much Sulfur (S) content is needed to lower the pH. When soil pH is high and Sulfur is low or insufficient to reduce the alkalinity of the soil, nutrient absorption by the roots of some trees may decrease. In the soil sample below, the Sulfur reading (in parts per million (ppm); see blue arrow) is 14 ppm. This indicates that Sulfur is high, but since the pH is also high. This could indicate a problem related to soil texture.

• Should you add more Iron (Fe) into the soil for your yellowing Pin Oak (or River Birch or White Pine, etc.) to help green up the foliage? Well, if the soil in this sample report above came from the property with those trees, we can see that the soil already has a very high concentration of Iron (see green arrow) at 154 ppm. Therefore, additional Iron is likely unnecessary.
• The same may apply if we were trying to resolve a Manganese (Mn) deficiency in a yellowing maple tree to help restore summer season color to the foliage. According to the Analysis Results example above, Manganese is 72 ppm is considered very high. (See orange arrow)

HOW TO GET YOUR SOIL TESTED

Related articles:

• Soil and Water pH – Part 1: What is pH?  https://ucnfa.ucdavis.edu/news/soil-and-water-ph
• Soil and Water pH – Part 2: How is nutrient availability affected by pH?  https://ucnfa.ucdavis.edu/news/get-cultured-part-2-soil-and-water-ph
• Soil and Water pH – Part 3: How do fertilizers affect pH?  https://ucnfa.ucdavis.edu/news/soil-and-water-ph-part-3
• Understanding and Applying Chelated Fertilizers Effectively Based on Soil pH  http://edis.ifas.ufl.edu/hs1208
• Chelates – What are they and What do they do? (PDF) https://www.gchydro.com/pdf/GreenCoast%20Hydroponics-IS-NUT-0413-The%20Science%20Behind%20Chelates.pdf
• Predicting Soluble Nickel in Soils Using Soil Properties and Total Nickel  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0133920