With storm season just around the corner, one topic of concern on many minds is damage to and from trees. Depending on the intensity of the storms and the condition of the trees, damage from high winds, heavy rainfall, and lightning can be quite severe. Cracked or broken branches, stem failure, and root failure are some of the main concerns, but also the risk and liability of damage to people and property.
If your tree is damaged, there are some steps to deal with the situation. First and foremost, consider the safety of yourself and others around you. Inspect the tree from a distance first looking for the following:
Heaving of the ground indicating potential root failure
Damage to limbs and/or the trunk of the tree
Hanging branches can fall to the ground resulting in injury or death
Be aware of utility and power lines. Trees can become charged by coming in contact with live wires. All utility lines should be considered energized and dangerous.
If you find your trees damaged from a storm hiring an International Society of Arboriculture (ISA) Certified Arborist to perform a risk assessment will help guide your decision of how to manage your tree. To find an arborist near you and verify credentials use the link at Find an Arborist, Trees are Good, International Society of Arboriculture (ISA). For more information, you can also view Trees and Storms: Understanding Damage, Risk and Recovery, an informational Got Nature? Blog article from Purdue Extension.
Purdue Landscape Report: Many of the leaf spot diseases we observe can cause premature leaf drop in affected plants, which can reduce plant vigor if the disease is severe enough and a large proportion of the canopy falls in one season. Elm trees are susceptible to a number of different anthracnose fungi, including Ophiognomoniaintermedia, Gloeosporium betulae, Cryptocline betularum, and Cylindrosporium sp. Cryptocline is the fungus that we encounter the most frequently on samples submitted to the lab for diagnosis.
Figure 1: Cryptocline leaf spot on Elm (photo by Paul Bachi, University of Kentucky Research and Education Center)
Figure 2: Cryptocline leaf spot on a young elm shrub. As the density of leaf spots increases, the leaf blade turns more yellow. (Photo from Purdue Landscape Report)
Figure 3: Mature Cryptocline lesions which are tan in color and have black fungal structures within (photo from Purdue Plant & Pest Diagnostic Laboratory)
Symptoms
Leaf spots may start as small, round chlorotic lesions that slowly expand over time (Figures 1 & 2). Eventually, a necrotic spot with a purple/black border and tan or white center will form (Figure 3). Lesions may begin to develop on a leaf vein and instead of being circular will follow the vein a little, creating a thin necrotic lesion (Figure 4). With increased leaf spot development, large areas of the leaf blade will turn yellow and eventually necrotic, before it falls from the tree (Figure 5). Leaf drop will typically occur in the lower canopy, areas where there is less air movement and higher humidity; however, epidemics occur during periods of we weather that can cause significant leaf drop. Leaf loss typically occurs in the summer (late July to mid-August).
Figure 4: Lesions of Cryptocline located on leaf veins, creating elongate necrotic lesions instead of the typical round lesions located elsewhere on the leaf. (Photo from Purdue Plant & Pest Diagnostic Laboratory)
Figure 5: Elm leaves which have turned yellow or necrotic and fallen prematurely from the tree. (Photo from Plant & Pest Diagnostic Laboratory)
Figure 6: Close up image of Cryptocline leaf spots with acervuli. (Photo by Paul Bachi, University of Kentucky Research and Education Center)
Life Cycle Cryptocline is only known to colonize the leaves, so it overwinters in fallen leaf tissue. In the spring, the fungus will produce ascospores which are carried in the wind to infect young elm leaves. Once initial lesions progress, black fungal structures (acervuli) will form in the necrotic tissue and being producing asexual spores (conidia) in a sticky substance, which can be spread via rain (Figure 6). The conidia act as a secondary infection cycle where it will infect foliage and create new leaf spots continuously throughout the growing season as long as the environmental conditions are conducive.
Management
Like other leaf spot pathogens that do not infect stems, removal of the foliage in the fall can reduce inoculum for the following year (though won’t eliminate the disease). Providing fertilizer (where needed) and water (hot and dry periods) will help mitigate some tree stress, as stress can predispose plants to increased disease severity. Fungicides are not normally recommended for mature trees as it is impractical to get coverage across the entire canopy, but could be practical in a nursery setting if symptoms are observed and leading to leaf drop. It is still early in the season, but the next few weeks are important to monitor for some disease issues that may explode later in the season.
For other information on management of foliar disease problems, please see the following link: Foliar Fungal Disease Management.
Damage to the cambium layer can cause serious health issues for the tree.
One of the most dangerous pests of trees is humans, especially humans with equipment. Lawn mowers and weed trimmers can cause injuries that create a hazard when an injury leads to tree disease or death. This publication explains why the damage is so dangerous and suggests ways to protect your trees.
Defended by Bark
The site of injury is usually the root flare: the area where the tree meets the turf and gets in the path of the mower or trimmer. The root flare, like the rest of the trunk, is protected by bark, which guards a very important plant transport system just behind the woody bark layer. Specialized tubes move nutrients and water between the roots and leaves to keep the tree alive. Any damage to this transport system can affect tree health and the tree could die.
Old damage from mowing can create a serious risk in the landscape
The bark layer can vary in thickness on different tree species. It can be more than an inch in thickness or less than 1/16 of an inch on young, smooth-barked trees such as maples and birches. This isn’t much protection against string trimmers and mowing equipment, especially on young, newly planted trees.
Damage Done
Any damage to or removal of the bark and the transport system can cause problems for a tree. Even when a tree tries to recover from a wound, leaves and branches often decline and die back, because food and water pathways were destroyed. Although a large wound is generally more serious than a smaller one, repetitive wounding adds up to greater trouble for the tree. If the damage extends completely around the base of the tree (a situation called girdling), the tree ultimately dies.
Recent damage from mowing equipment leads to decay and dieback in the tree
All tree wounds are serious when it comes to tree health. No matter what size the wound is, the damage done is irreversible. The tree must devote a great deal of energy and many resources into trying to seal off the damaged area to prevent further complications. The wounded area is an opening for wood-rotting organisms and decay fungi to enter and cause further damage. These microorganisms often attack the injured bark and invade adjacent healthy tissue, greatly enlarging the wound and extending the damage. Trees can be completely girdled from pathogen attack following injuries.
Fungi that are active on the wound surface can also deteriorate the structure of the woody tissues beneath, decaying and weakening the tree. This weakened, structurally unsound tree may eventually die and become a hazard to people around it.
Preventing Problems
Newly planted, young trees need our help to become established in the landscape. They are the trees most commonly and seriously affected by maintenance equipment.
Mulch rings can provide a healthier environment as well as a visual cue to keep equipment away.
However, injury to these trees can be avoided easily and at very low cost if you follow one or more of these suggestions.
Physically remove turf or prevent grass and weeds from growing at the base of the tree. This lowtech solution can eliminate a potentially serious problem.
Spray herbicides to eliminate vegetation around the base of the tree to decrease mowing maintenance costs. Be sure to use care when applying herbicides around trees. Carefully follow label directions.
Add a mulch ring, when possible, to help reduce the competition for water and nutrients. Mulch or other ground coverings reduce mowing requirements in the landscape.
Add a 2˝ to 3˝ layer of mulch on the root zone of the tree to provide an attractive and healthy environment for the tree to grow. This also provides a visual cue to keep equipment away from the tree.
Add trunk guards or similar devices to give the tree additional protection. White, expanding tree guards can help help trees withstand equipment contact and also can help to reduce winter injury.
Trees are a valuable asset to your property and are important to our environment. Every tree contributes to the urban forest and improves air and water quality in your neighborhood. Protect and preserve these growing assets by keeping mowing and weed-trimming equipment away from tree trunks. The damage lasts and it cannot be undone. Don’t create a hazard!
Join Purdue Extension forester Lenny Farlee in this episode of “A Woodland Management Moment” as he explores the considerations for growing high timber-quality black walnut on purpose. Learn about what black walnut requires to grow well, its visual characteristics and the timeline of this plant in openings. Watch the video to discover some of the management strategies you can use gradually develop these black walnut stems for timber markets.
If you have any questions regarding trees, forests, wildlife, wood products, or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Unhealthy trees can fail, causing potential damage to nearby homes
Trees provide many benefits for our homes, businesses and properties. If a tree is defective, however, it may become a hazard. It is important to understand that tree owners have a duty to inspect and maintain their trees. All property owners should take reasonable steps to protect themselves by involving a qualified consultant or certified arborist.
The primary responsibilities of the arborist are to assess the potential for tree failure, advise owners of the consequences of failure and recommend the proper measures to prevent and abate failures. In assessing and managing trees it is important to create a balance between the inherent risk a tree poses and the benefits provided by the tree. Risk tree management begins with these basic steps:
Reduce tree liabilities: The property owner or manager has an obligation to periodically inspect trees for unsafe conditions. Since all trees have risk associated with them, regular inspection compels the owner or manager to evaluate the amount of risk they are willing to assume. Tree risk assessment is an important part of a program to determine if a tree is structurally sound or has the potential for failure. Inspections show that the tree owner is actively managing their trees and could reduce the owner’s liability if a failure occurs.
Inspect regularly: Trees should be assessed through inspections by a qualified arborist, preferably an International Society of Arboriculture Certified Arborist. Further inspections should be conducted after major weather events. At a minimum, trees should be inspected every five years or according to the owner’s risk tolerance.
Document and maintain records: Every inspection should be recorded and kept on file for future reference. These records are important for several reasons. Past evaluations can show how a tree has changed in its health and structure over the years. Also, written assessments are beneficial in liability claims and court cases. These written evaluations could minimize liability if a failure occurs and a claim is filed against the tree owner.
Inspect trees for health conditions and defects during the tree risk assessment.
Develop a site policy and care plan: Every property manager should create and implement a policy for tree risk. This includes developing a standard of care, an inspection process and mitigation of property risk. Routine care and scheduled maintenance for all trees is essential.
Mitigate tree risk: Tree owners should make every effort to reduce risk with proper pruning and health care practices. Consider all options before deciding on removal. If possible, move or remove the “target” (see definition in “Tree Risk Assessment” section). Install structural support systems where feasible. Modify site conditions to improve the environment around the tree. Risk mitigation requires a process of logical options focusing on protecting the target and preserving the tree.
Schedule tree work: While evaluating trees for risk, the inspector should note any tree maintenance needs. The inspection can determine the timing and priority of work needed. The work should be prioritized first for safety and then for tree health. Consider potential risk, activities around the tree, level of acceptable risk and the needs of the client.
Create good tree planting strategies: Identify planting needs and locations that become available as trees are removed or destroyed. Improving the health and safety of the landscape requires an understanding of management principles, such as species selection and diversity. Also consider the impact of site infrastructure, including utilities, streets and sidewalks, and choose the right tree for the right place. Select trees known to thrive under local conditions and sustainable as long-term investments in the property
Tree Risk Assessment
For a tree to be considered hazardous it must be defective either in some part or as a whole, with risk for failure and a target that is threatened. Trees are declared hazards if assessments have been completed and mitigation is required to prevent a failure from causing damage affecting the target. To understand the implications of this concept, tree owners need to know some common terms of tree risk management.
Identify potential targets for tree failure.
A target is people, property or activities that could be injured, damaged or disrupted by a tree failure. Tree owners must carefully assess the area around homes, playgrounds, sidewalks and parking areas. Is the target static, moveable or mobile? Consider whether people can be kept away or separated from the target area. Also, assess the target’s value and potential. Review the target zone, which is the area where the tree or a branch is likely to strike when it falls, to determine consequences of the tree’s failure. The target zone should include the areas inside a circle around the tree, which is at least as wide as the total tree height.
Risk is the combination of the likelihood of a tree failure event and the severity of the possible consequences of that event. Every tree has the potential to fail; however, only a small number of failures actually cause injury or damage. It is impossible to maintain trees free of risk. Some level of risk must be accepted by the owner.
Hazard is a likely source of harm and is identified as the tree part or parts which will affect the target zone. For example, an entire tree or a single branch could be determined as a hazard. Hazards are identified during tree assessments, and tree owners are required to take steps to minimize the risk of damage from failure.
Individual tree characteristics must be considered when conducting evaluations for defects and failure potential. Evaluations should take a systematic approach, assessing the potential for tree failure, understanding the impact of such failures and outlining a plan of action to prevent and mitigate these failures. Tree owners should fully understand the site factors and characteristics of the tree species. There are several contingencies that influence tree failure potential and risk. These include soil type and saturation, wind exposure, pest damage, poor growing conditions and poor pruning practices such as topping.
Among the characteristics to consider when conducting tree risk evaluations are:
Defects — severity and location. Decay, cankers, cracks and other positive indicators of weakness in the roots, stems and branches may need immediate attention if a target is present.
Species characteristics. Some tree species possess weaker wood, a susceptibility to decay, poor growth habits and potential for pests. They could be more likely to fail after wounding because of poor ability to wall off internal decay or health issues.
Canopy size, shape and weight distribution. This is especially true in situations where a tree is exposed to windy conditions, is leaning or has a poor stem-to-canopy ratio.
Crown architecture. Poor branching and similar characteristics can create high-risk situations in strong winds and other weather conditions.
Plant health and vigor. This determines how a tree can overcome wounding or pest infestations.
The overall size of the defective part. A predetermined rating system, which outlines critical thresholds, should be considered and incorporated into the tree’s risk management plan.
Tree Inspections
Assessments should include a thorough examination of each section of the tree. A systematic approach using standardized evaluation methods aids the process. Review the canopy (crown), branches and root zone to check for signs of failure. These include:
Dead, diseased, dying or broken branches.
Thinning or poor canopy health.
An unstable branching pattern, overextended or weakly attached branches, or cracks in the stems.
Cracks or decayed areas in the main trunk.
Exposed or decayed roots, heaving of the soil, fungus growth or cracks in the soil around the root plate.
Recurrent inspections to determine tree health and condition are critical for successful risk management programs. Trees in active-use areas should be inspected annually for defects and conditions leading to failure. Inspections are necessary after storms to ensure excessive loads have not exceeded the strength of the tree and its parts. Also, be sure to note trees with a history of failures or those with problematic structure, for more frequent monitoring and inspection. A good database and archive of tree evaluations is a critical strategy in the overall risk management plan.
Figure 1. Runoff from roads surfaces into trenches can quickly form gullies from soil erosion if not quickly repaired following utility work (Purdue Landscape Report)
Purdue Landscape Report: Each of us utilize mobile devices and daily consume services that require fiber and other utility infrastructure. Necessary utility work along roadways often leaves sunken trenches, compacted soil for lawns that are uneven or stripped of vegetation. If damage is significant, check with the utility provider, as many companies have restoration policies or reimbursement options for affected homeowners. However, subcontractors and varying degrees of action by utilities can make this a frustrating process.
But a few timely steps can speed recovery and simplify the process rather than dealing with later weed overgrowth or washing overtime. Begin by removing rocks, excess gravel, and construction debris. Loosen the sides of ruts or where excess soil remains beside a trench with a rake or shovel to level out and improve water infiltration and root development. If the area has settled or ruts are present after a period of time, regrade to match the surrounding lawn and ensure proper drainage away from the roadway and sidewalks. Use extra caution when these areas are collocated with drainage or susceptible to water over wash as your work can be whisked away. In some cases, ignored sunken trenches and ruts can be back filled with highly deteriorated mulch to help bring back life to the soil if one has patience to let time continue to run its course and seed later into the mellowed, high organic matter soil.
Next, incorporate quality topsoil or compost to rebuild soil structure and fertility.
Figure 2. Sunken trenches from utility work that have been overgrown with grass/weeds can be a hazard for one walking or when mowing. Often the easiest fix if one is willing to be patient is to add composted mulch into the trench which will help fill to help soil and have less disturbance. Mulch is also much easier to shovel than top soil.
Choose a grass seed mix appropriate for your region and light conditions and apply it evenly over the prepared area. Lightly rake the seed into the soil and cover with straw mulch to reduce erosion and conserve moisture. Keep the area consistently moist with light, frequent watering until seedlings are well established, typically 2–3 weeks depending on weather. If the season is not fit for seeding grass (i.e. July) try seeding a temporary cover crop like buckwheat that will attract pollinators and give short term cover while choking out weeds.
For larger or highly visible areas, sod can provide an instant fix, though it is both expensive and requires careful watering to root successfully. Once new grass reaches 3–4 inches, begin mowing and apply a light fertilizer application to encourage growth.
In summary, it depends on the time frame and the urgency you have to fix a recently created problem based on its location. For problem areas that have existed over time where weed growth has already occurred, using composted mulch to fill sunken trenches or ruts may be the easiest, while using mowing to manage weeds during summer and seed after lighly working surface more towards late summer or early fall.
Walk through many forests in Indiana today, and you might not notice what is missing until you look up. Ash trees, once a common part of these woodlands, have rapidly disappeared due to the invasive emerald ash borer. Since its arrival in the early 2000’s, this small beetle has killed millions of ash trees across the state (Figure 1).
Figure 1: Dead ash tree killed by emerald ash borer
But what happens after ash trees are gone? Do new trees grow in their place, or do forests begin to change in unexpected ways?
To answer these questions, researchers revisited long-term forest monitoring plots across Indiana that were first established in the 1990s, before emerald ash borer was present. By comparing forest conditions before and after widespread ash mortality, we can begin to understand how these ecosystems are responding to one of the most destructive invasive forest pests in North America.
Even though young ash trees are still present in many forests, their numbers are dropping quickly (Figure 2). In some areas, ash seedlings have declined by more than 70 percent over the past decade. While a few saplings remain, very few are surviving long enough to replace the large trees that have been lost.
This suggests that ash is unlikely to return as a major component of Indiana forests anytime soon. As the remaining seeds in the soil are used up and fewer young trees survive, ash may become a much rarer species on the landscape.
As ash declines, other plant species are filling the gaps, but not always in the way we might expect.
Instead of fast-growing canopy trees taking over, many forests are becoming dominated by shade-tolerant species that thrive in low-light conditions. Native plants like spicebush and pawpaw are increasing in abundance, often forming dense layers in the understory. These species can make it difficult for other trees to establish and grow.
Sugar maple, another shade-tolerant species, remains common as seedlings but is not always successfully growing into larger trees. This creates a bottleneck where young trees are present, but few make it into the next stage of forest development.
At the same time, invasive plants are becoming more common in many forests following ash loss. Species such as bush honeysuckle and multiflora rose are increasing, especially in areas where ash trees have died.
These invasive plants can outcompete native vegetation, further limiting the ability of forests to regenerate diverse tree communities. Once established, they often persist and spread, creating additional challenges for forest management.
When large trees die, we might expect more sunlight to reach the forest floor, helping new trees grow. However, in many Indiana forests, the loss of ash is creating only small openings in the canopy rather than large gaps.
Figure 2: Ash regeneration in the understory.
These smaller gaps favor shade-tolerant plants rather than species that need full sunlight to thrive. As a result, forests are gradually shifting toward communities dominated by shrubs and slow-growing, shade-adapted trees.
Ecologists often refer to this process as mesophication, a transition toward cooler, shadier, and more moisture-loving forest conditions. Over time, this can lead to forests that are more uniform and less diverse.
The loss of ash is more than just the disappearance of a single group of trees: it is part of a broader pattern of change driven by invasive species, altered disturbance patterns, and shifting forest conditions.
Without intervention, many forests may continue to develop dense understories dominated by a small number of species, including invasive plants. This can reduce tree diversity, limit wildlife habitat, and alter how forests function over time.
While forests are resilient and will continue to grow and change, they may look very different from those of the past.
Landowners, land managers, and the public all play a role in supporting healthy forests. Monitoring for invasive species, promoting a diversity of native trees, and managing dense understory growth can help improve forest regeneration.
As research continues, understanding how forests respond to the loss of species like ash will be critical for guiding conservation and management efforts in the years ahead.
Discover the essential guide for anyone looking to plant forest trees or shrubs in Indiana. Whether you’re a first‑time landowner or an experienced conservationist, Planting Forest Trees and Shrubs in Indiana walks you through the 10 proven steps for establishing healthy, resilient plantings that thrive for generations. From choosing the right species to preparing your site, planting with confidence and ensuring long‑term success, this publication distills expert forestry knowledge into clear, practical advice. Ready to transform your landscape and leave a lasting legacy?
This publication provides an abbreviated 10-step approach to plant and establish healthy, productive forest and conservation plantings in Indiana. Successfully planting trees and shrubs involves much more than sticking the right end in the soil.
In this edition of ID That Tree, Purdue Extension Forester Lenny Farlee introduces us to Virgin’s Bower clematis, a native vining plant found in Indiana that’s especially noticeable when it blooms later in the growing season. Often seen climbing over nearby vegetation or spreading across open spaces, this species adds both beauty and ecological value to the landscape. Learn where Virgin’s Bower is typically found, how to recognize it and how it compares to a similar invasive look-alike. Whether you’re a student, landowner or simply curious about native vines, this video offers a quick introduction to this attractive and useful Indiana species.
If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Purdue Landscape Report: When talking about invasive species, specialists are most commonly talking about some kind of plant or insect that is making an impact on landscape plants, soil, or hardwood. Most of these species are relatively easy to understand, with a biology that typically resembles that of a native counterpart. Wood-boring insects, vining plants, and fast-growing shrubs all have similar native species that landowners deal with on a regular basis. And then, some invasive species are just plain weird, like the invasive hammerhead worm!
Hammerhead worm (photo from Arun T P, Bugwood.org)
Hammerhead worms, sometimes called shovel-headed garden worms, are a type of land planarian, or flatworm. Flatworms are worm-like organisms that lack the segmentation of earthworms and have the ability to regenerate from parts and pieces. Hammerhead worms belong to a subset of planarians, the genus Bipalium; while there are a few native species of Bipalium, most are from tropical regions. It is believed that hammerhead worms have been present in North America for long time, preferring environments that stay warm and moist through most of the year. Hammerhead worms are named for their spade-shaped head and typically have bright colors with dark lines running the length of their bodies. They are often found in indoor spaces and greenhouses that are temperature controlled and maintain humid conditions. Hammerhead worms can also be found living under rocks, fallen trees, or anywhere that can maintain a high enough relative humidity. While some flatworms are able to live in drier conditions, Bipalium need moisture in order to survive.
Members of Bipalium are predatory, consuming invertebrates like earthworms, snails, slugs, and some soft-bodied insects. Once they capture a prey item, they envelop it in a mouth-like organ located on the underside of their bodies. The primary issue with hammerhead worms is the potential damage they can do by preying on beneficial organisms that maintain soil and plant health. Hammerhead worms, and all other planarians, lack a closed body plan that uses a one-way digest system. Once they eat something, it is digested and waste is excreted through that same mouth-like opening. Some members of Bipalium can also use a toxin called tetrodotoxin to subdue their prey; however, they only produce a small amount and lack a way to use it on a larger organism. While they are often confused for more dangerous species, the Bipalium in North America do not represent a human health concern. Just keep any pets or children away from them, and if found, and use gloves if you’re forced to handle them.
As mentioned above, one of the more unique traits of Bipalium, and planarians in general, is their capacity to regenerate new individuals from parts and pieces. A piece as small as 1/279th of the whole can regenerate into a new individual. Do not attempt to chop up or crush hammerhead worms, or you may be dealing with several dozen when new worms develop in two weeks. However, even though it seems like hammerhead worms could reproduce very quickly, it’s still fairly uncommon to see one. If found, place it in a bag or bucket with either salt, alcohol, or vinegar until the worm is dead. As long as you do not cut or chop up the worms, it is very unlikely you’ll have to deal with more than one at any given time. Just keep your eyes open and remember to report any sightings to 1-866-NOEXOTICS!
