The Root of Many Plant Problems in Central Ohio: Soil pH

By Walter Reins
ISA Certified Arborist
January 16, 2025​

[Please note: This article was revised and republished on 1/16/25 from its original publish date of 4/24/24.]

You’ve probably heard the term pH. You may even think “I know this one - it means something is either acidic, neutral, or alkaline”, and that wouldn’t be wrong. But what does that mean and why does it matter? What determines the pH of soil, water, or even the human body? Like the periodic table of elements, pH may be something that reminds you of high school chemistry class, something you’ve filed away under the “when am I ever going to use this?” section of your brain, long ago forgotten and collecting dust ever since it was put there. While pH is far from being an endorphin-producing topic, it does significantly influence plant growth and overall health in your landscape. Let’s discuss the role that soil pH plays in nutrient availability, soil chemistry, and even microorganism activity, and why it matters for your plants.

pH and How It’s Influenced

pH stands for “potential of hydrogen”, and is a measure of the acidity or alkalinity of a solution, ranging from 0 to 14 with 7 being neutral. A value below 7 is considered acidic while a value above 7 is considered alkaline (or basic). This scale represents the concentration of hydrogen ions present, with acidic solutions having a greater number of ions and alkaline solutions having fewer ions. In soils, that concentration of hydrogen ions is influenced by things such as the parent rock material that originally formed the soil, human activity, climate, and the presence or lack of organic matter. In turn, the resulting pH will influence the availability of nutrients essential for plant growth, microbial activity that helps with nutrient absorption, and soil chemistry that influences the breakdown of soil particles into more usable forms. Of the influencing factors mentioned above, parent rock material and the presence or lack of organic matter often go hand in hand and are the most significant influencers in our central Ohio landscapes. Central Ohio largely consists of limestone bedrock, which naturally has a higher pH than what’s preferable for most plants. So you might ask “Well, how is it then that any plants can be healthy and thrive in central Ohio?”. The answer is organic matter. In an undisturbed, natural environment like the forest, years and years of organic matter have formed on top of the infamous “Ohio clay” subsoil that we encounter in our backyards. The source of this organic matter comes from falling leaves, dead branches and trees, and dying organisms just to name a few, that collect on the forest floor year after year, decade after decade. These are all things we tend to remove from our landscapes to keep them tidy, which results in a lack of organic matter formation over time. For more on how to address this topic, check out our Arbor Ed article “Leave those Leaves!”

Nutrient Availability

Chlorosis in a pin oak tree in Bexley, Ohio

pH influences the availability of essential nutrients in the soil by changing their level of solubility. This simply means that pH will determine whether or not these nutrients are in a form that can be absorbed by the tiny roots and roots hairs of plants. Most plants will prefer growing in soil with a pH range between 6-7, slightly acidic to neutral. When the pH is out of its optimal range for a particular plant (generally too high in central Ohio), the plant’s growth may slow, it may lose overall health and vigor, or conditions like chlorosis can develop because that plant isn’t getting the nutrients it needs to carry out essential functions for growth. Chlorosis, or yellowing of leaf tissue, is a very common condition in central Ohio and can be seen most often with trees like pin oak, red maple, white pine, and river birch. It’s interesting to note that these are trees that are either native to Ohio or an adjacent region. In their natural habitats where organic matter is abundant, soil pH is lower and nutrients are readily available for uptake. The parent material, derived from limestone and having higher pH levels, does not affect the trees since the absorbing roots are largely growing in the organic layer above it. In our backyards however, carpeted with lawn but cleared annually of leaves, higher pH levels can quickly cause issues even with otherwise healthy trees.

Chart showing availability of essential elements at various pH levels

Microbial Activity

pH affects the activity of microorganisms in the soil. These microorganisms are essential for plant health, helping plants to absorb certain nutrients, or aiding in the breakdown of organic matter into available forms for your plants. Certain fungi, bacteria, or insects that benefit a particular plant will naturally thrive in the same pH that is ideal for that plant. Encouraging the proper pH for your plants in turn helps to foster a healthier population of these important helpers in the soil. In the same way that our own bodies are influenced by the health of our gut bacteria, plants rely on microbial activity in the soil. Without it, they can struggle to carry out essential functions for proper growth and overall health.

Soil Chemistry

Similar to nutrient availability, pH can affect the chemistry of the soil and determine whether or not the available nutrients will be absorbed by roots. It also influences the composition of the soil, helping certain minerals to break down into smaller molecules, ultimately affecting the charge of soil particles and the ability for the soil to hold on to essential elements that could otherwise be removed from the soil. A good example of this would be a soil’s ability to retain certain nutrients by preventing them from getting washed out of the soil by irrigation or rainfall. Acidic soils tend to be better at retaining more of these charged nutrients. It's no coincidence then that most plants prefer acidic or slightly acidic soils, as the lower pH makes those soils richer in nutrients and more “user friendly” for plants.

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Soil pH plays a significant role in the overall health of trees, shrubs, and other plants in our landscape. A little bit of knowledge can go a long way in helping to understand the unique issues you may have in your central Ohio landscape. Below is a list of a few things you can consider in determining what’s best for your yard.

• Have a soil sample from your yard submitted for analysis to help determine if there is a pH issue or nutrient deficiency.

• If you know that you have higher pH levels, consider planting trees and shrubs that are more tolerant of alkaline soils.

• Try incorporating more organic matter into your soil by allowing leaves to decompose in landscape beds over the winter, and consider enlarging groundcover or mulch beds around trees (less lawn)

• Have root zone invigoration work done for trees that are struggling with nutrient deficiencies and/or soil compaction.

• Apply pH lowering products to landscape beds with particularly sensitive trees or shrubs (note that this is something that generally needs done annually, as permanently lowering the pH of soil with additives is next to impossible).  

As always, one of our 20+ ISA Certified Arborists® are happy to provide a free tree quote by giving us a call at (614) 895-7000 or by visiting RussellTreeExperts.com/Quote

Additional Tree Preservation Articles!

Walter Reins I Regional Manager, Russell Tree Experts

Walter became an ISA certified arborist in 2003 and has a degree in landscape horticulture. He has 25 years of experience in the tree and landscape industries and originally began working at Russell Tree Experts in 2011. Walter is also the owner/operator of Iwakura Japanese Gardens, a small design/build/maintenance firm specializing in Japanese-style gardens, and also offers responsible tree planting for all landscapes.

Tree Work in the Winter?

By Mike McKee
ISA Certified Arborist®
January 2, 2025

[Please note: This article was revised and republished on 1/2/25 from its original publish date of 1/10/24.]

“Can we get this work scheduled before winter kicks in?” “Do you complete tree work during the winter?” These are questions that I am often asked as the hibernal or winter soltice has arrived. In many cases, winter is the only time we can complete certain projects. This is due to the fact that many diseases and insects are not active, canopy visibility is increased, impact on landscapes is lessened due to winter’s colder conditions, and wildlife regulations are not in effect. Winter can be the perfect time for tree work.

Nitidulid beetles can transmit oak wilt between March 31st and October 15th, making this an unideal time to prune oak trees. On the flip side, October 15th to March 31st is the preferred time prune oak trees as nitidulid beetles will not be actively feeding in the Midwest, thus reducing the risk of oak wilt.

Winter is an opportune time for tree pruning to minimize the risk of insect and disease issues. For oak trees and elm trees, oak wilt and Dutch elm disease respectively are two devastating diseases that are be transmitted by insects (and root grafts) attracted to fresh pruning cuts. (Learn more here!) These insects are typically not active during the winter months, thus making approximately October 15th to March 31st the preferred time to prune oak and elm trees. If pruning cuts are required outside of this time window due to reasons such as storm damage, we highly recommend painting the cuts to minimize the risk of attracting the insects that can spread these diseases. Other trees that can benefit from winter pruning is the Rosaceae family which includes apples, pears, plums, and other fruit-bearing trees. The pathogens that infect many of these trees with diseases such as fire blight and black knot are typically not active during the winter months. Black knot is also much easier to see and prune out when the leaves are not present on our plum trees. Sanitation between cuts and proper disposal of these branches is imperative to slow down the spread of this disease.

Another reason for performing tree work during the winter months is the minimization of turf impact. Winter typically provides an absence of perennial and annual plants that are often planted under trees. Clients also tend to store their yard art, furniture, and other items that could be damaged during pruning and removal operations. This allows for our crews to be more efficient as less time is spent preparing the drop zone and moving items to a safe location prior to beginning any tree work. Thirdly, the winter months tend to be colder which provides a harder, sturdier ground that is more resilient to damage from limbs or equipment. As always, we do place mats on the ground if turf impact is a concern regardless of the time of year. Therefore, winter pruning becomes much more productive since there are fewer items that could be damaged otherwise.

Certain job sites such as golf courses, public parks, and street tree pruning, just to name a few, are performed during the winter months as there tends to be less pedestrians, allowing for better focus, less interference, minimized risk, and overall a more efficient and safe work zone.

With the absence of leaves on the trees, it is much easier for the trained eye to identify structural issues. Some structural issues may require a cable or even brace rods to secure your favorite tree in your landscape. Winter is also a great time to observe decay, fungi, or other pathogens that may not be visible during the summer when leaves are abundant and present. It is also the best time to observe cavities throughout the tree that may not be noticed while leaves are present. Dead, diseased, and broken branches are also much more visible when the leaves are not present in the winter months. Our arborists are trained to be able to identify the difference between dead and live branches even during the winter months. This time also allows the arborist to make quick decisions on improving the structure of the tree while pruning in the most efficient time of the year.

One example of projects that must be completed during the winter is anything that falls under federal bat tree regulations. This typically includes public property projects where large trees need to be removed or the removal of any tree that could be a nesting site for bats. These regulations are intended to protect the Indiana Bat and the Northern Long-eared Bat, which are both currently endangered species. The importance of bats in our ecosystem is a story in itself. Bats typically overwinter in caves but move out to their nesting sites as early as April, therefore removal of possible nesting sites is regulated from March 31 through October 1. This is the main reason that the majority of our clearing operations and trail creation projects are completed during the winter months. To learn more about endangered bats in Ohio, read here!

As you can see, there are many beneficial reasons and scenarios to have tree work performed in the winter! Every day can be a good day for tree care. Check out the video below to learn more. To request a free tree work quote from one of our 20+ ISA Certified Arborists®, visit RussellTreeExperts.com/Quote or give us a call at (614) 895-7000!

ADDITIONAL ARBOR ED ARTICLES!

Mike McKee | Regional Manager, Russell Tree Experts

Mike graduated from Hocking College in 1983 with a degree in Natural Resources specializing in urban tree care. He has been a certified arborist since 1991. Mike started his career in the private industry in 1985 before becoming a municipal arborist in 1989. He retired after serving thirty years before joining us at Russell Tree Experts in Sept. of 2018. His love of trees has never waned since trying to climb up the ridges of the massive Cottonwood tree in front of his childhood home.

Magnolia Scale: They're Back!

By Mike McKee
ISA Certified Arborist®
June 20, 2024​

Hello! We have decided to revisit the topic of magnolia scale and add more information to this previously published article as we are in the middle of a larger magnolia scale infestation compared to last year (2023).

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Please note: This article was originally published on 8/9/2023 and was revised and republished on 6/20/2024.

Is your magnolia tree turning black? Is it attracting ants, flies, bees and wasps? Is there a sticky substance covering the leaves and everything under the plant? If you look closely, you will also see white blotches on the twigs throughout the tree.

This is an invasion of magnolia scale like we have not seen in several years. They happen to thrive in warm summers with abundant moisture. The population is building and is very apparent this year.

The insect overwinters on twigs and is inconspicuous to the untrained eye until it starts feeding and producing honeydew. Honeydew is the very sweet, sticky substance secreted by the insect that in turn coats the leaves and anything under the plant. This is what attracts other insects to the plant. Eventually the insect covers itself with a waxy coating that protects it while feeding. These are the white blotches we are now seeing on the plants starting early summer through August.

Nymphs emerging from a recently plucked adult Magnolia Scale

The juvenile stage of magnolia scale emerges from these waxy coatings (the adults) in mid to late August through September as crawlers. This is when scale are most vulnerable to insecticides and we attempt to control their population. We typically recommend 2 to 3 topical insecticide sprays during this period spaced a couple weeks apart for the best control of the insect due to the extended emergence. During seasons with larger infestations, it is unlikely that insecticide sprays will completely eliminate this insect. The overall goal of plant healthcare is to keep the population at a threshold that minimizes damage and maintains aesthetics of the host tree.

If the tree’s owner is concerned about the population of magnolia scale before the appropriate window for insecticide applications is open, there are a few DIY options that can be done. First, the insects can be scrubbed off from branches and leaves in June and July. This is when the adults are visible before the hatch begins. You could also prune out heavily infested Interior branches to help reduce numbers. Be sure to completely dispose of any pruned branches as the insect will still hatch. Spraying the trees with a medium pressure garden hose can also eliminate some insects as well as reduce the honeydew on the plants.

The insects feed by sucking sap out of the tree. If left untreated the scale population can grow to levels that will cause decline and eventual death in your tree.

Another issue with Magnolia scale is the occurrence of sooty mold which is a byproduct of the honeydew produced by the scale. It is a black fungal growth which is what most people notice first. Although this generally does not harm the tree, it is very unsightly.

In closing, if you have a magnolia in the landscape, give us a call and we will dispatch a certified arborist to your property to come out and complete an evaluation of the tree and make recommendations for the best management strategy. Timing is everything.

Sincerely,

Mike McKee | Regional Manager, Russell Tree Experts

Mike graduated from Hocking College in 1983 with a degree in Natural Resources specializing in urban tree care. He has been a certified arborist since 1991. Mike started his career in the private industry in 1985 before becoming a municipal arborist in 1989. He retired after serving thirty years before joining us at Russell Tree Experts in Sept. of 2018. His love of trees has never waned since trying to climb up the ridges of the massive Cottonwood tree in front of his childhood home.