Why are Humans Blind to Understanding Trees?

Posted on August 3, 2023 by landscapeexpert

I watched a terrific webinar hosted by Mr. Neville Fay, an gifted, learned arborist in England. Here are some takeaways from the Webinar.

Humans identify with other living animals because humans are animals. anthropomorphism, the interpretation of nonhuman things or events in terms of human characteristics, as when one senses malice in a computer or hears human voices in the wind. Anthropomorphism is a human characteristic hindering are ability to fully comprehend and understand the plant kingdom, particularly trees and plants.

Why are humans blind to the plant kingdom? Is it because humans have become increasingly separated from nature? Since we are a part of nature, indeed we came into existence in nature, what happens when we separate ourselves from nature, if we become alienated from nature are we alienated from our own self?

Our language and thoughts create and limit our world and influences our opinions. “The tree which moves some to tears of joy is, in the eyes of others, a green thing that stands in the way”. Our language limits how we think, how we view the world, and explains why we cannot fully understand and appreciate trees.

We often define a tree based on its location, aesthetics, function or monetary value. Trees in forests are viewed for the timber value. Old, mature, dying trees are viewed as dangerous threats to our well being. Trees life expectancy is often viewed from a “useful” perspective, usually resulting in damage, flawed or senescent trees being removed rather than allowed to progress through their lifespan? This may make sense in the urban environment, but what happens when a supposedly dying or dangerous tree is allowed to continue living beyond its “useful” lifespan?

These trees defy our attempts at defining what a tree is. They are remarkable living beings that have the ability to define or refine what a tree is, can or should be. Every tree pictured above has retrenched itself into a new being, growing new tree parts or new trees from original broken or decayed stems and trunks. Obviously they have no timber value, but appreciating there ability to survive and recreate is very inspirational.

Trees have several life stages, young to early mature, full to late maturity, ancient and or sessile. We frequently never allow trees to exist in their ancient life stage, especially in the urban environment.

As trees enter the ancient life stage, they undergo crown and root retrenchment, dramatically increasing their functional complexity and reiteration.

Here is an ancient olive tree, a tree completely hollowed out, the original trunk is gone, yet it has drawn upon resources to interweave multiple stems and roots into a retrenched healthy olive tree. Is this one tree or multiple trees or even a forest of trees? This tree has no timber value, and would most likely never be allowed to exist in an urban setting. Yet It can only be viewed as awe inspiring, magnificent.

While trees are a part of ecosystems, a single mature or ancient tree is in and of itself a complete ecosystem, supporting an abundance of animal, bird, insect, fungal and bacterial life.

Did plants and animals evolve from a single source? A theory called Endosymbiosis posits plants and animals evolved from the same original source. The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). This theory explains the origin of eukaryotic cells.https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kaiser)/Unit_4%3A_Eukaryotic_Microorganisms_and_Viruses/07%3A_The_Eukaryotic_Cell/7.8%3A_The_Endosymbiotic_Theory

The separation between animal and plant cells diverged when mitochondria evolved from bacteria evolving into animals versus chloroplasts developing from bacteria evolving into algae and plants. Records depict trees have lived and evolved with humans for thousands of years. Their existence and importance to humans cannot be overestimated.

Trees cannot escape where they grow, they become soil farmers, they are conductors of the soil orchestra of microorganisms. Soil is alive, a living breathing thing. Where trees are allowed to flourish, they enrich soils, thereby creating the endless cycle of life. When we develop and compact soils, we are killing a living environment. Mega agribusiness utilizes monocropping to produce our food, a practice that increases their profit while killing off biodiversity and depleting our soil resources. https://www.greenmatters.com/p/what-is-monocropping

Leonardo de Vinci understood the complexity of trees and their roots, positing the root structure being a mirror image of above grade stems and limbs.

Soil compaction is the single greatest threat to soils, thereby our future.

We need to embrace trees, eliminate bias views of trees based on our own anthropomorphic views. We cannot exist without trees, they provide the oxygen for our planet, without trees, humans would not survive. And even if somehow we managed to survive, I for one could not imagine a world without trees.

Saving the Giant Sequoia Forest

Posted on June 13, 2023 by landscapeexpert

For several years, climate change and drought created conditions for uncontrolled California wildfires. These wildfires burned with such intensity, several Giant Sequoia, (Sequoiadendron giganteum), forests were heavily damaged. We have lost approximately 20% of the entire species, over 10,000 Giant Sequoias have been destroyed the past three years alone.

Although these magnificent trees are fire adapted, with an incredibly thick outer bark protecting the cambium within, the recent fires burned with such incredible intensity scores of trees were incinerated. Another fire adaptation are the Sequoia cones that normally open after a fire, distributing thousands of seeds that germinate and replenish the burned groves. Yet the fires were so hot, even the cones were destroyed, so the trees produced no new seedlings.

All of the groves are located in a relatively small band on the western slope of the southern Sierra range. Due to climate change, the southern Sierra range has become a dryer environment, very different than 2,000 years ago when these magnificent trees first germinated. As the forest regenerates, shrubs, fir, and cedar have replaced the Sequoias.

Sequoia seedlings require a lot of water to germinate and grow into juvenile trees. The hotter, drier climate and competition with other less favorable species, reduces Sequoia germination and ultimately, the survival of the species. Imagine Sequoia National Park without any Sequoia trees. Your kids and grandchildren might end up never being able to visit and enjoy these incredible trees. My father took me to the park when I was a child. My love for this species influenced my decision to study horticulture, eventually making my profession, first as a landscape contractor, later as a consultant and expert witness as certified and registered consulting arborist.

Fortunately, the Save the Redwoods League has teamed with the US Forest Service and National Park Service undertaking replanting thousands of redwood seedlings throughout several burned forest areas. The goal is to reestablish groves that can be managed to become fire resistant again. It is a massive undertaking, that has never been tried before. While the odds of any seedling becoming a massive, thousand year old monarch are depressingly low, (one in 10 billion), it is the morally right undertaking for mankind. Without restoration, the redwood groves will convert to shrub lands, a sad ending for the official state tree of California.

Read about the restoration efforts in this article from the Los Angeles Times.https://landscapeexpertwitness.com/wp-content/uploads/2023/06/Los-Angeles-Times-eNewspaper.pdf

Bromeliads in the Landscape

Posted on January 14, 2023 by landscapeexpert

With spring time on the horizon, it was time to start sprucing up my landscape garden. I try to make the garden interesting using a variety of plant materials with differing form, texture and foliage color. My latest planting incorporates bromeliads into the landscape. There are countless species to select from, their form, leaf color, texture and flowering are extremely unique and incredibly beautiful. Fortunately, there is a fantastic nursery in north San Diego County specializing in bromeliads and tillandsia, www.birdrocktropicals.com

Visits are by reservation only, but well worth it. Although I’m a horticulturist, bromeliads are a specialty species I had little actual knowledge on species planting and maintenance requirements. I have a very difficult planter area that is full shade in the winter, full sun in the summer. Another planter changes varies from shade to part shade seasonally.

I received a great education while guided through the nursery, learned a great deal about bromeliad breeding, potting and maintenance. Another great tip they provided was leaving the plant in the container while planting in the landscape. Bromeliads, similar to orchids, are tropical understory plants. They are adapted to very poor, thin tropical soils and do not like heavy, clay poorly drained soils. Unlike typical ornamentals. they also prefer contained environments, smaller plants do not like being potted into large containers. They should remain in smaller containers until they grow multiple pups, filling the container to the point where watering becomes difficult.

Another advantage of planting them in their containers is being able to remove them if the environment becomes to shady or sunny for the individual plant. I’m excited about these beautiful plants, hoping they grow and multiply!

Why Attorneys Hire an Arborist Expert Witness

Posted on February 3, 2022 by landscapeexpert

Whether an attorney represents a plaintiff or defendant, they hire an expert who will provide compelling testimony to support their client. Sometimes, multiple experts from a variety of disciplines may be required. When should an attorney consider hiring a certified or registered consulting arborist as an expert witness?

Living with trees implies accepting a certain amount of risk in exchange for the wonderful benefits trees provide. While the risk of a tree limb or whole tree failure resulting in a fatal injury is low, hazards caused by trees that result in personal injury or property damage lawsuits are not uncommon.

Tree species and proximity to infrastructure may be a factor in accidents with personal injury or property damage. Tree roots seek out moisture regardless of their location. Structural roots emanate from the trunk to the edge of the crown, also known as the drip line, then small moisture absorbing root grow far beyond. Tree root systems may grow 1.5 times the tree crown diameter.

Trip, Slip and Fall Accidents

In the urban environment, tree proximity to hardscape may result in roots growing beneath concrete sidewalks and paved streets while seeking moisture. Roots will grow into adjacent water meters and sewer laterals, especially older leaking, permeable infrastructure. Once established beneath a paved surface, a root continues growing, over time enlarging in diameter.

Over time, these surfaces may begin to lift along the crack or expansion joint. Adjacent sidewalk panels may lift several inches, resulting in a hazardous condition for pedestrians and bicyclists.

Uplifted sidewalk panels resulted in bicyclist personal injury lawsuit

After sidewalk was removed, large structural roots were observed beneath the sidewalk.

Multiple roots damaged the sidewalk, created the hazardous condition and resultant accident.

Eventually root enlargement lifts concrete infrastructure, including water meter boxes and sidewalks. Cracks may develop across a sidewalk panel, in my experience, most concrete sidewalk uplifts occur along an expansion joint.

In their pursuit of moisture, roots from neighboring trees ignore property lines. They can grow beneath garage slabs and foundations, especially in situations where there has been a water or sewer leak beneath the slab. Moisture discharged beneath slabs, footing and foundations create an attractive environment for root development.

Neighbor’s Ficus tree root grew beneath their garage slab, resulting in property damage lawsuit.

Roots suspected of lifting sidewalk panels and water meter box that resulted in personal injury lawsuit.

After sidewalk was removed, large roots observed growing around the water leaking water meter.

Installing street trees within small concrete confined planters is an invitation for root damaging infra-structure. Leaking water meters, fittings and sewer connections increase soil moisture, an invitation for root growth.

A root penetrating a leaking sewer lateral or potable water meter pipe or fitting will quickly establish a mass of roots within and surrounding the pipe. Root growth may continue from the sewer lateral into the public sewer main. Over time, the root growth may block or cause a sewer back up to neighboring properties.

Roots deform a sewer lateral beneath garage slab.

Section of removed sewer lateral filled with roots.

Improperly designed, installed or maintained sprinkler systems may result in over-spraying paved pedestrian sidewalks. Regardless of cause, their is no reason to allow sprinklers to over-spray onto paved surfaces, it wastes a vital resource while creating an obvious slip and fall hazard.

Park sprinklers over-spraying a public sidewalk, resulted in a personal injury lawsuit.

Tree failures and forensic tree risk assessment

Tree limb and whole tree failures may result in personal injury and property damage lawsuits. Whole tree failures may occur due to loss of load bearing structural roots, whether due to root rot disease, construction impacts, mechanical root damage, or soil failure. Limb drops may occur for a variety of known reasons, typically the failure occurs during a weather event. Sometimes, a tree will drop a limb for unknown reasons, referred to as sudden or summer limb drop. Stems may contain defects such as cankers, decay, and cracks that may be predisposed to failure when enough force exceeds the wood carrying capacity. Forensic tree risk assessment may determine why the tree failed and whether the defects were open and obvious.

Stem failure resulted in personal injury and property damage lawsuit.

Tree and landscape appraisal for fire damage, trespass and vandalism

California has suffered countless wildfires the past two decades, resulting in substantial property damage. Tree appraisal for loss due to fire may be an important aspect in legal cases, especially when several major utilities are under scrutiny for causing wildfires.

The same holds true for tree loss or diminution in value due to trespass and vandalism. You may love your tree, but your neighbor may not. Neighbors frequently engage in tree disputes, sometimes resulting in trespass and vandalized trees. You may love your tree, but your neighbor may not.

Avocado groove scorched from wildfire in Fallbrook. Appraisal performed for insurance and tax purposes.

Oak tree property damage claim due to Thomas fire.

Tree and landscape appraisal for property damage lawsuit caused by Thomas fire mudslide.

Palm tree nursery burned due to vandalism, appraised palm value for property damage lawsuit.

Bamboo hedge poisoned by neighbor, property damage lawsuit.

Tree loss due to neighbors pruning, resulting in property loss lawsuit.

Arboriculture standard of care

Tree service contractors may become involved in a lawsuit for failing to satisfy the industry standard of care. When a tree failure occurs, the landscape maintenance or tree care contractor may find themselves as defendants in a lawsuit. A plaintiff may contend the landscaper or tree care company should have known the tree had defects but was the contractor responsible for risk assessment?

A C-27 landscape contractor may not be a certified arborist or provide arboricultural tree care, certified arborist may not be a trained or knowledgeable of Tree Risk Assessor Qualified, (TRAQ).

To determine a contractor’s standard of care, I examine their membership in industry associations such as the California Landscape Contractor Association, (CLCA), the International Society of Arboriculture, (ISA), the American Society of Consulting Arborists, (ASCA), and Professional Tree Care Association. I determine whether the certified arborist and tree care professionals adhere to the American National Standards Institute, (ANSI) A300 arboriculture standard practices and Z133 safety requirements. I check their standing on the California State Licensing Board.

In summary, personal experience, education and training are essential qualifications an attorney looks when selecting an arborist expert witness. Having expertise in multiple disciplines is an added benefit. My qualifications as a professional horticulturist, a C-27 landscape contractor, a certified arborist, registered consulting arborist and tree risk assessor qualified and land development manager enable me to opine on a broad array of landscape, tree, plant and land development issues.

Why Did My Tree Fall Over?

Posted on January 12, 2022 by landscapeexpert

Structural failures occur when the stresses due to forces acting on a tree exceed the strength of the tree or or the tree/soil connection supporting the tree. Even the structurally strongest tree will fail when a load is applied that exceeds the carrying capacity of one or more of its parts.

Typically, it is a combination of several defects or conditions causing a structural failure. A root or stem decay, or poor structure combined with an unusual loading event, such as a strong wind storm, are frequently associated with tree failures.

While there are several factors involved in a failure, they are characterized as a soil or a root failure.

Root decay, root collar and buttresses rots are often associated with a root failure. Root rots typically begin from wound resulting in an injury. Root decay fungi infect through small diameter roots. Roots that have been stressed due to lack of oxygen due to soil compaction, excessive soil moisture, construction trenching, excavation and cultivation may allow entry of a root decay fungi into the roots. The decay may then progress from the feeder roots into the structural root system. The decay may be located on the underside of larger roots.

When the decay progresses into the heartwood or base of the tree, it is referred to as basal decay, a butt or collar rot. Rots kill water adsorbing feeder roots. This affects the trees ability to adsorb water and nutrients from the soil. This condition may be manifested as dieback within the tree crown. Foliar tip dieback progressing into twig, stem and limb dieback are potential symptoms of a progressive root rot. Tree leans may also be a sign of a compromised root system.

Root rots may be difficult to detect and determine the severity of the infection. Depending on the tree species, location, maintenance practices, root rots may take years before the rot begins to compromise the structural roots. Root rots can directly cause structural root failure or contribute to wind throw.

Tree failure may be due to the soil rather than tree roots. Soils influence root development, therefore it is important to assess how site conditions affect root development. Assessing soil factors such as volume, depth, moisture, compaction and quality, (texture, fertility and pH) directly affect root growth and structural support.

Small soil volume will limit tree root growth and development, especially strong structural roots. This is especially relevant for city urban street trees that are often installed in small planters surrounded by asphalt and concrete streets and sidewalks where space is minimum and roots are often cut and damaged. Underdeveloped root systems may be structurally weak, limit tree growth and health, which reduces the tree’s ability to adapt to the loads it experiences. Construction impacts including grading cuts and fills, trenching, and excavation may severely damage root systems resulting in root rots and or lack of structural support.

Adequate soil depth is required for a well anchored tree. Trees with shallow root systems tend to be more prone to failure than trees with well established deeper root systems. Shallow soils may occur due to underlying bedrock or urban infrastructure. Grading cuts and fills for development may result in soil layering, resulting in saturated soils or over-irrigated soils. Soil type and texture affects drainage, coarse textured sandy soils drain quickly, heavy clay soils retain moisture for long periods of time.

Surface compaction is common in urban development due to pedestrian and vehicular traffic. Compaction and flooding result in reduced oxygen within the soil. Roots require oxygen, as it is depleted within the soil to due compaction, flooding or over-watering, feeder root rots may begin, progressing into larger structural roots.

Assessing root damage is challenging for most lay people. If your tree is in decline, leaning or looks different than it used to, hiring a certified arborist who possesses the specialized training in tree risk assessment is highly recommended.

If your tree has failed, the two most obvious clues as to cause is the appearance of the root ball. If the failed tree has a large portion of the root ball with soil intact surrounding the roots, most likely it was a soil failure. If the tree has nothing but blackened roots sticking out of the root ball with little or no soil clinging to the roots, most likely the tree failed due to a progressive root rot.

San Diego Arborist

Top 10 List: What we have learned about trees

Posted on July 28, 2021 by landscapeexpert

While reading the Western Arborist, an tree industry publication, I came across a top ten list of what we have learned about trees by Nelda Matheny and Jim Clark, both very well known researchers, teachers, lecturers and industry titans. I have had the honor to meet both, read their work and attend their workshops. So when I came across their top ten list, I felt compelled to share it with you.

10. Our view of trees has evolved from being niceties to being necessities.
9. Tree preservation requires space.
8. Tree care practices can have either positive or negative consequences.
7. Soil health is vital to tree health and requires protection and nurturing .
6. Structural defects in mature trees can largely be prevented through selection and early care.
5. Trees are both biological organisms and mechanical structures.
4. Tree care applies general information to specific genotypes.
3. Tree risk assessment is an imprecise endeavor.
2. We must use science to guide tree management.
1. Education is a lifelong process.

Bonus: It’s not enough to know about trees.
We have to know things that affect trees and things trees affect.
We have to describe and present our work.
CERTAINTIES
1. Trees will continue to grow and require care.
2. Trees will become more important to people and cities.
3. If you stop learning the world will pass you by.
Nelda Matheny & Jim Clark, Western Arborist, Fall 2020

As a certified arborist, tree risk assessor qualified, registered consulting arborist, C-27 landscape contractor and professional horticulturist, I have spent my personal and professional life involved with trees. They are my passion and profession, I’m extremely grateful for spending a lifetime with trees. For me, trees provide beauty, aesthetics and functional benefits. But most important, trees provide me an emotional connection to our planet. We could exist without trees. They bring me happiness and beauty, they uplift me and provide calm and peacefulness in times of need. They are truly magnificent biologic organisms we should maintain, share, and protect for future generations.

Busting Common Gardening Myths: Trees and Taproot Development

Posted on May 24, 2021 by landscapeexpert

One common garden myth is trees have long tap roots extending straight down into the ground. This is a common misconception of root growth, an incorrect perception shaped by “common sense” assumptions, not scientific evidence. Most of us have seen seedlings germinate and immediately grown a “tap root” into the soil. The root growth occurs prior to the seedling growing new leaves. Once the tap root is established, new leaves begin to appear.

People generally think the tap root continues to grow downward, in essence resembling an enlarged carrot or a Christmas tree form. The misconception of the tree crown and root system mirroring each other is commonly depicted in drawings of a lollypop shaped tree with identically shaped root system.

Another misconception is tree roots stay beneath the tree canopy, only growing out to the drip line of the tree. The misconception is excurrent shaped trees (holiday form Xmas tree, pyramidal shaped) grow similar shaped narrow, pyramidal tap root system, while decurrent, broad shaped tree crowns, (shade tree form), must have a more branched root structure, resembling a giant broccoli cluster.

Humans like symmetry, the perception that the root system mirrors the crown form is commonly depicted in tree renderings. Where the crown and root system mirror each other. This is also seen in fertilizers with directions to apply near or at the “drip line”, the outer edge of the tree crown from which rain-water drips, as if this represents the majority of the tree’s absorbing roots.

Why does a tree grow a taproot?

Certified arborists know the taproot structure is a juvenile feature with specific functions important for a young tree, including:

Anchoring a young tree
Creating a vertical structure for lateral root development
Storage mechanism for sugars
Serves as part of the transport system for conducting nutrients and water to the trunk and canopy.

Root growth is dependent upon three factors for survival: water, oxygen and nutrients. If any one of the three factors is missing, root growth and development stops. Downward taproot growth slows as oxygen becomes increasingly limited with soil depth. Compacted soils also are oxygen deficient due to crushed or damaged soil structure, limiting oxygen within soil micro and macro pores. Flooded and or poorly drained soils are also oxygen deficient, with the same limiting effect on taproot and regular root growth and development.

As a taproot encounters limiting soil conditions, it begins to branch, adding lateral root development to explore soil resources within the top 12-18” of the soil.

Mature tree with no taproot, Photo courtesy of Western Arborist, Winter 2020.

Certified arborists understand how construction activity compacts the soil, thereby compressing the soil structure, damaging soil porosity resulting in limited oxygen, water and nutrient availability. As a result, urban tree maturation is dependent upon lateral root development, most of the structural rooting occurs within the top 12-18” of the soil. It is estimated a trees functional root system extends two to three times the crown diameter at its widest point. The juvenile taproot is subsumed by the rapidly developing lateral root system.

Understanding the root system location and lateral structure within the top 12-18” of the soil profile is vital to managing irrigation and maintenance practices.

Structural roots emanate from the trunk, they hold the tree upright but do not absorb any water or nutrients. The fine root hairs responsible for water, oxygen and nutrient uptake may be located a considerable distance from the tree trunk, often at and beyond the edge of the tree crown, known as the drip line and beyond. Certified arborists and horticulturists understand proper irrigation methods, such as avoiding applying water on the root collar, designing water distribution where feeder roots are located beneath the crown, toward the drip line and beyond.

In summary, Southern California soils do not support deep taproot development. Construction and development compact soils, resulting in reduced soil porosity, water, nutrient and oxygen retention, three vital factors required for root development. Over 80% of a tree root system is within the top 12-18” of the soil. Taproot formation is a juvenile feature that is replaced by a horizontally growing lateral root system that extends two to three times the crown diameter. Water and nutrients are taken up through the fine root hairs located beneath the crown, near and beyond the tree drip line.

Consider using a certified arborist, horticulturist or landscape contractor, industry professionals who utilize industry standards, plant science, personal knowledge, experience and education to promote plant health.

Is Your Tree Safe?

Posted on March 15, 2021 by landscapeexpert

Jeremy Rappoport, President of Rappoport Development Consulting Services LLC, made his video presentation at the ‘Tree for Tomorrow Starts Today’ Workshop. The zoom video workshop was attended by several hundred professionals from water districts, agencies, tree service and tree consultants, landscape architects and other industry professionals.

The goal of the workshop was to increase tree health and reduce impacts created by urban heat islands, and properly selecting and caring for trees today to ensure a greener tomorrow.

Mr. Rappoport’s presentation, entitled ‘Is Your Tree Safe’ examines his use of tree risk assessment for forensic investigations in tree failure accidents. The presentation depicted tree roots lifting sidewalks creating trip and fall hazard and roots damaging infrastructure, limb failures, and tree protection during construction.

The presentation offer solutions for minimizing root issues during the project design phase and early use of a certified arborist as part of the design team.

A recording of the full video presentation is available at https://youtu.be/QpRL0aQD26s

Trees for Tomorrow Start Today’ Workshop

Posted on March 1, 2021 by landscapeexpert

Hello, this is Jeremy Rappoport, president of Rappoport Development Consulting Services LLC (RDCS). The workshop goal is to increase tree health and reduce impacts of urban heat islands by properly selecting and caring for trees today to ensure a greener tomorrow. The workshop is sponsored through the University of California Agriculture and Natural Resources.

As an experienced legal expert witness, I consult for defendant and plaintiff attorneys and insurers in the fields of arboriculture, horticulture, landscape and land development. My credentials as a certified arborist, registered consulting arborist, tree risk assessor qualified (TRAQ), C-27 landscape contractor, and B.S. in ornamental horticulture enable me to opine on relevant legal cases.

My presentation, ‘Are Your Trees Safe?’ focuses on legal cases involving roots lifting sidewalks creating trip and fall hazards, root, limb and trunk failures, and the forensic application of tree risk assessment. I will propose solutions to reduce tree potential tree risk during the design / development process for planners, landscape architects, civil engineers and government agencies and how to reduce current tree risk before the a defect results in a accident and resultant lawsuit.

The ‘Trees for Tomorrow Start Today’ Workshop also features ‘Working Together Across Professions ‘Success Stories’, presented by several distinguished speakers, followed by roundtable discussions. The workshop is scheduled on Tuesday, March 9, 2021 via Zoom. Click here for the registration link.

Tree Roots Lifting up Sidewalk?

Posted on August 11, 2020 by landscapeexpert

Who is Better Qualified to Opine on Root Damage, Civil Engineer or Certified Arborist?

I was retained by a defendant attorney to determine whether her client’s tree was responsible for lifting the adjacent civil sidewalk that resulted in a plaintiff trip and fall lawsuit. Based on the photographs and tree species, White mulberry (Morus alba), I was fairly certain her client’s tree was responsible for the sidewalk damage.

The attorney retained me and requested a site inspection and tree root assessment. I trenched adjacent to the sidewalk and within a short time, encountered a three-inch diameter root growing under the sidewalk. Further excavation revealed a network of two to four-inch diameter roots that had grown under the sidewalk, resulting in the tree roots lifting up the sidewalk panel, creating a hazardous condition resulting in a trip and fall accident.

I informed the attorney that tree roots lifting up the sidewalk, or root encroachment from her client’s tree resulted in the sidewalk damage, she said her civil engineer expert claimed it impossible for a tree root to lift a concrete sidewalk. I questioned the engineers knowledge and experience with trees, was the civil engineer a certified arborist or horticulturist?

Although the answer was no, she felt his qualification as a civil engineer was superior to my qualifications as a certified arborist, tree risk assessor qualified, registered consulting arborist and a college educated horticulturist. Her dilemma was having two experts who disagreed and she requested I alter my opinion.

I told the attorney altering my opinion to suit her needs was unethical, and I removed myself from the case.

What Causes Tree Roots To Lift up a Sidewalk?

The common myth is trees have tap roots that grow straight down into the soil. While this may occur in very deep, loam soils, the reality is most containerized nursery grown trees lose their tap root in the container. Once planted in our poor Southern California soils, when the tap root encounters physical soil obstructions, such as rock, clay or hardpan, the tap root divides and grows multiple roots around the obstacle, forming a fibrous root system. Tap root grows into fibrous root system.

Trees require a spreading root system to maintain structural stability. Trees dissipate energy generated during a storm or wind event by transmitting leaf, limb and trunk movement down to the roots. A spreading root system anchors the tree movement and dissipates the energy far more effectively than a single tap root system.

Most tree roots grow within the top 24-inches of the soil horizon. Roots in top 24″ of soil. Over time, structural tree roots (2-inch diameter and greater) growing within a shallow soil adjacent to sidewalks, footings, foundations, walls or othersub-surface infrastructure may cause damage.

Just as a twig grows into a branch, and then a limb, roots increase in length and circumference. Irrigation water, sewer or water service leaks increase subsoil moisture beneath sidewalks or garage slabs, creating a perfect environment for root growth.

Cracked garage slab

As the root circumference increased, it exerts pressure on the concrete slab or footing above the root. Depending on the species, root diameter might increase 1/8-1/4” annually.

Within five to eight years, a small feeder root may grow to one-inch in diameter or greater.

Ficus root cracked the garage slab

The root growth may be compared to the action of a hydraulic jack, as the circumference increases, the upward pressure on the sidewalk or slab may crack and or eventually cause tree roots to lift the sidewalk. Concrete lifting may often occur at an expansion joint between concrete panels

Sidewalk lifted at expansion joint

Root network beneath sidewalk.

Roots seek out soil moisture, they can and will grow under walls, footings and garage slabs. Roots are opportunistic, leaky plumbing, old cast iron sewer lateral or water services contribute to the soil moisture needed for roots to flourish.

Sewer lateral root damage

Roots may infiltrate pvc, abs and cast-iron pipe through even the smallest of cracks or holes.

Once inside, the roots expand in size and quantity, eventually completely clogging the utility.

If the tree crown has grown over a sidewalk or adjacent structure, it is a reasonable assumption structural roots (two-inch diameter and greater) have grown under the sidewalk, slab or footing.

Root growing under house footing

Planter areas confined by concrete pose one of the greatest risks for root damage. City sidewalks often incorporate small, square planters within the sidewalk easement.

Roots lifting water meter and sidewalks

Confined planters quickly fill with structural roots, as well as damaging girdling root. As the tree crown grows, so to do water absorbing feeder roots. Over time, root mass and size increases, structural roots may begin to grow beneath concrete improvement while seeking out moisture.

Leaking water meter, high soil moisture, confined growing space.

The tree pictured above and to the right had a leaky water meter adjacent to the small sidewalk planter. The leaky service provided idea soil moisture conditions for the roots to lift the water meter box, adjacent sidewalks and crack the curb and gutter.

Preventative measures to minimize root encroachment include a variety of root barrier methods. All root barrier systems work best when the tree is installed. Once roots have enlarged and matured, barrier mitigation is not successful.

In summary, our Southern California poor, shallow soils do not support deep tree tap root systems. Most trees grow fibrous spreading root systems. Structural roots emanating from the root collar extend to the edge of the tree crown, (drip line). Most structural roots growing beneath sidewalks range from two to four inches in diameter, lifting sidewalk panels on average one-two inches. Trees growing in confined planters or adjacent to concrete, utilities or foundations may develop structural roots capable of lifting, cracking or damaging adjacent improvements.

Dealing with legal issues due to tree roots lifting up a sidewalk?

Attorneys should select an expert based on the case criteria, not simply a title, license or certificate. Choose an expert most appropriate to address the cause of the problem and develop opinions based on sound, industry practices.