Top 10 List: What we have learned about trees

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.

Trees for Tomorrow Start Today’ Workshop

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?

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.

A Horticulturists Local Neighborhood Walk

I took my usual walk through local neighborhoods surrounding Balboa Park in San Diego.  A glorious spring day, I couldn’t help but marvel at the beautiful ornamental landscape trees, shrubs and vines in bloom everywhere!  Very uplifting, glad plants are not affected by the virus!

Arborist Online Learning Opportunities in the Covid Era

In a recent blog, I discussed using online media for a site online site inspection involving a Torrey pine tree root conflict with adjacent asphalt paving.  That marked the first time I used an online media tool rather than being physically present at the site.  My client and I used Facetime to conduct the real time inspection.

As the restrictions ease, I believe the use of online media such as Zoom, Hangouts, Facetime etc will increase.  I have already presented this concept to a legal client in Northern California concerning an irrigation inspection.  Do I really need to fly from San Diego to San Francisco, rent a car, drive to the site, observe irrigation defects, then reverse the process returning home or, can I watch the inspection over the web?  The level of scrutiny required depends on the individual case.

A slide from Dr. Smiley’s presentation

Like so many other industries, the tree industry is rapidly adapting to the new Covid – 19 reality.  Today, I attended an online Zoom seminar titled Sidewalks, Urban Plazas and Tree Roots.  This seminar was presented through the ISA Southern Extension.  I believe it was originally going to be part of a “normal” ISA Southern Association Annual meeting that was cancelled due to Covid.

The online presentation occurred through Zoom with over 1000 arborists throughout the U.S. and other countries attending. The topic concerned tree roots damaging sidewalks, presented by Dr. Thomas Smiley.  Once a few technical glitches were adjusted, the presentation was almost identical to what I had experienced attending many seminars.

The slides presented alongside the audio streaming from Dr. Smiley was easy to view.  I became immersed in the content and found myself taking pics of some of the slides.  The topic provided test data results using different techniques designed to reduce root intrusion beneath sidewalks.

Incorporating root growth inhibitor practices

 

The presentation lasted an hour, same amount of time I’m accustomed to when attending a seminar.  Although I already knew a great deal about the topic, I still came away with new information for use in my practice, including a great specification detail incorporating multiple root growth inhibitor practices that may reduce sidewalk damage due to roots.

In the past month, I’ve been able to continue my consulting practice from my home office.  I’ll continue to utilize more online media tools, whether for learning, conducting site inspection work, and client meetings.  I believe these new opportunities are one of the (few) beneficial results from the Covid-19 virus.

I recently provided a client with a proposal to develop landscape maintenance specifications for commercial properties located in several different climatic regions.  The proposal did not include any site visits.  All data collection would occur online through various means.  Using online data collection versus conducting multiple site visits saved the client thousands of dollars.

I’m looking forward to these new opportunities utilizing online media sources as potential replacement for physical presence.  Hopefully it will prove an efficient, effective, cost saving technique without sacrificing product accuracy.

 

 

 

Online Site Inspections with Corona Virus: A New Paradigm?

The corona virus and resulting stay at home order has prevented me from scheduling or attending site inspections.  I require site inspection for most forms of consulting work, including as a consulting arborist or expert witness.

  • Tree failures, health and risk assessment
  • Tree inventories
  • Tree and nursery appraisals
  • Tree roots and infrastructure damage.
  • Landscape appurtenances creating trip and fall hazard.
  • Obscured landscape hazards, grade changes
  • Irrigation operation, maintenance issues

A client wanted me to attend and observe asphalt paving taking place adjacent to an 80 year old Torrey Pine.  I had previously consulted on preserving this tree during construction on an adjacent property.  The client was repaving his driveway on the alley, the pine is right on the edge of the paving.

Due to California stay at home orders, I informed the client I could not be present to observe the paving to make recommendations, so we used the Facetime app and did an online site observation whereby I watched in real time as the work was being performed.  I was able to give the client recommendations in real time.

Moistened towel protect surface roots

He was concerned about root damage, and rightly so.  Some of large buttress roots would be impacted by the paving.  Instead of cutting, I recommended covering the roots with wet towels, fabric etc, then placing moistened sand base, then pave over the roots.

Moistened sand placed over protected roots

As terrible as it is, the corona virus has created many new ways for industries to re-invent how they do their business.  This was the first time I have attempted on online site inspection and it worked!  This may not be applicable for the types of investigations I perform, but there is a great new tool I can use for certain types of investigations during stay at home and even beyond.

Asphalt paving over protected roots

 

The financial savings for the client are obvious.  Travel costs for me to travel to Los Angeles, Orange or Inland Empire typically range from $500 to $1000 or more if hotel stay is required.

Not all inspections can be performed remotely.  Forensic investigations that require measurements, excavations, sampling, testing etc may not be applicable.

Since this is new to me, it will take some real time client cases for me to determine how and when I can utilize this new tool.

Old Growth Redwood Destruction Continues

I read an L.A. Times article discussing ongoing logging of redwoods in Humboldt County.  In a battle spanning several generations, tree sitters and eco-activists are putting their bodies on limbs in redwood tree tops to prevent logging.

This is not the first time tree activists have climbed hundreds of feet up old growth redwoods to prevent logging the tree and surrounding trees.  It reminded me of a remarkable novel I read called “The Overstory” by Richard Powers.  The novel is about people and their interaction with and the affect specific trees and forests.

It primarily focuses on loss of old growth redwoods and firs in the pacific northwest and activists actions to prevent tree and habitat loss.  However, the novel was historical, taking place several decades ago.  Yet it appears old growth logging in Humboldt county continues to in present.

I recently visited, camped and explored the Jedediah Smith State and National Redwood park, not far from where present day logging takes place.  For me, the thought of logging off trees that are hundreds to over a thousand year old is difficult to accept.

We have commercial redwood farms for harvesting lumber.  Of course, it does not possess the grain, size, color and characteristics of true old growth redwood trees.  If we want future generations to be able to view and experience the incredible creation of a true, old growth tree, we MUST stop logging and preserve this resource.

Joshua Tree Extinction by End of Century?

I just read an article in the Los Angeles Times about a potential listing of the Joshua tree as an endangered species.  The western Joshua tree, Yucca brevifolia, is one of two genetically distinct species that occur in California.  It range extends from Joshua Tree national park westward along the northern slope of the San Bernardino and San Gabriel mountains, northward along the eastern flank of the Sierra Nevada and eastward to Death Valley.

Approximately 40% of the western tree range is on private land, the eastern range is centered in the Mojave National Preserve and eastward into Nevada.

After decades of climate change, development, drought and wildfires, the species is facing a rapidly increased the risk of extinction.  State Department of Fish and Wildlife Commission will decide in June whether to accept the department’s recommendation to declare the tree an endangered.

As usual, there are two sides to the issue.  Conservationists see this as a triumph of state environmental law while critics claim it as a misguided overreach because Joshua trees are already protected under many city and county ordinances and within the 800,000 acre national park.

Environmentalists argue existing state and local ordinances are largely inadequate at protecting species habitat loss, the endangered species listing will finally provide a statewide protection for the species, including requiring wildlife managers devise a recovery plant for the species, which could limit development in SoCal real estate.

The Joshua tree exists in high desert communities such as Yucca Valley or Hesperia, communities with lower average median household incomes.  They are concerned the listing would impose additional burdens to real estate development, making it tougher to improve their property or curtail new development in their communities.

However, researchers warn time is running out.  The tree’s range is contracting at lower elevations, its reproduction has come to a halt.  Trees are failing to reproduce at lower, hotter elevations.  They could become extinct in California by the end of the century!

This would be a terrible outcome for a truly incredible species.  This remarkable species deserves protection.  I believe this tree, in its own way is as majestic in its high desert setting as the coast redwood.  These are species distinct to our California heritage.  The Joshua tree deserves protection for our future generations to enjoy, marvel and be uplifted by this unique species.

Download a pdf of the article here:  Los Angeles Times – eNewspaper

California Olive Trees Dying from Exotic Pest Infestation

Olive tree displaying decline symptoms

With so many trees dying in natural and landscape settings, I’ve observed a disturbing trend throughout San Diego, and I assume most of the state.  Property owners allowing dead and declining trees, palms and shrubs to remain in place.  The problem with this practice, aside from aesthetics, is the dead plant may serve as a vector, whereby flying insects such as beetles, leaf hoppers, spittle bugs etc. may spread the disease to other uninfected trees.

Over the past decade, drought and climate change has taken a toll on millions of trees throughout California.  Drought weakened trees succumb to secondary invaders such as wood boring bark beetles.  There appears to be a continuous proliferation of new exotic pests resulting in diseases that are killing millions of trees in nature and within our urban forests and residential landscape settings.

Gold spotted oak borer

First collected and identified in 2004 was the gold spotted oak borer, (GSOB). This flathead borer is responsible for killing over 100,000 live and black oaks in San Diego County alone.  There is no effective prevention or cure.

Reports of the disease known as citrus greening, previously confined to China, appeared in Florida, threatening the entire U.S. industry.  The disease is a vector-transmitted pathogen by the

Citrus damaged by Asian citrus psyllid

Asian citrus psyllid.  This disease ravaged Florida citrus growers.  Once infected, there is no cure.

Another exotic pest first detected in Southern California in 2003 has been infesting hundreds of different species and is now established throughout the southland.

The Polyphagous shot hole borer is a small ambrosia beetle responsible for transmitting Fusarium disease to many tree species including avocado,

Sycamore bleeding from shot hole borer

box elder, coast live oak, maple, liquidambar, coral, sycamore and many other species. Fusarium is a vascular clogging disease for which there is no cure.

The list goes on and on.  Climate change and an ever more connected world will continue the trend toward future invasive erotic pests.

In early 2000, olive trees, (Olea europea) became very popular as a landscape tree, heavily planted throughout southland landscapes. For the past decade, olive trees have been declining from a number of diseases.  Two of the diseases are fatal, both display similar symptoms, making diagnosis difficult.

Foliage display tip and marginal burn symptoms

Symptoms appears as leaf marginal burning, tip dieback, leaf scorch, and loss of foliage color.  Defoliation proceeds from the top down and outside in toward the trunk.  Small twigs die back, eventually larger branches and entire limbs die. Depending on location and season, the decline may be rapid or slowly over the years.

 

Xylella or Verticillium?

 

Disease Infection

  1. Diseases known as quick decline, leaf scorch, or variegated chlorosis are caused by Xylella fastidiosa, the bacteria best known for causing Pierce’s disease on grapes, but also attacks citrus, peach, almonds, oleander, olives and many other species.
  2. Verticillium wilt affects olive trees in commercial and landscape plantings and many other species. The disease is caused by soil-borne fungi, Verticillium albo-atrim and dahliae.

Both are vascular clogging diseases, where the fungus or bacteria spreads throughout the vascular system, restricting water movement within the xylem tissue.  However, they have separate means of transmission. Unfortunately, neither disease has a cure, infected trees and shrubs decline over time, usually resulting in death.

Description and Spread

  • Xylella is transmitted by the glassy-winged sharpshooter, (Homalodisca vitripennis), leaf hoppers and spittle bugs. These vectors are xylem feeding insects.
  • The pathogen multiplies and spreads throughout the host tissue, restricting water movement through the xylem tissue.
  • Insect vectors feeding on infected trees (such as olive and oleander) may acquire the bacterium and carry it to new hosts.

 

Verticillium is a soil-borne fungus, it invades the root system of olives when the soil temperature is cool.

  • After penetrating through roots, the fungus multiplies within the xylem tissue, interrupting and reducing water movement from the roots to the leaves.
  •  Each disease clogs the vascular system, interrupting water movement from the roots to the leaves.
  •  Both diseases have similar symptoms making identification difficult.

Common Symptoms:  (not all symptoms may be present) 


Xylella:

  • Tip burn

    Leaf scorch beginning at the tip toward the stem (petiole).

  • Marginal browning, scorch and yellowing.
  • Twigs and branches dieback beginning in the upper crown.
  • Desiccated leaf and fruit drop.
  • Production of suckers.

    Crown dieback

 

Oleander infected with Xylella

 

 

 

 

Verticillium:

  • Symptoms appear in spring.
  • Newer leaves curl inward.
  • Dead fruit clusters remain attached.
  • Loss of leaf color and luster.
  • Leaf and fruit drop follow.

    Inward leaf curl

Progressive decline

 

 

 

 

Dead fruit retained

 

  • Individual branches and or large portions of the tree may die within one season.
  • The tree may not die, growth may develop on unaffected portions of the tree and suckering from the crown.
  • The new growth continues until re-infected; the cycle repeats the following year.

    Vascular staining

  • Vascular staining may be present.

Control

There is no cure for Xylella or Verticillium.  Recommendations for both diseases include:

  • Remove suspected plants immediately to prevent vectoring disease to other susceptible host plants, i.e.: olive, oleander, sweetgum, grapes, etc.
  • Integrated pest management to control insect vectors may help slow disease spread but spraying to control leafhoppers is expensive and futile.
  • Control of nearby weeds and grasses to help limit insect vectors.
  • Pruning out infected limbs may improve the appearance, but it is impossible to prune “below” the infected wood, so pruning does not get rid of the disease.
  • Fungicide applications are not effective.
  • Remove declining and dead trees immediately.
  • Replant with disease resistant species.

Avoiding the disease is most effective but not always possible.   Soils are easily contaminated with Verticillium from former planting and the pathogen may survive in the soil for several years, ready to infect newly planted susceptible species.

While greenhouse soils may be heat pasteurized to kill the fungus, that is impossible in the landscape.  Solarizing landscape soils has some effect at reducing verticillium infected soils.  Prior to planting, rototill and irrigate the soil as deeply as possible.  Cover the area with six mil plastic, seal the edges with soils to secure for six to eight weeks.

Effective cultural practices such as fertilizer application, irrigation management, weed and insect control may assist in preventing infection and possibly reduce the effects of the disease.  Most of these practices focus on improving plant vigor that help mask the disease, however these treatments are not curative.

It is important to note, many of the foliar symptoms described above may also be due to drought or poor irrigation practices.  There are also foliar diseases that may produce similar symptoms but are only minor and may not pose a serious threat.

Diagnostic laboratory testing is the definitive method for a positive identification of the disease. 

The important take away is this:  Don’t ignore decline symptoms in olive and other susceptible species, as the plant may be infected with a fatal vascular disease.  Declining and dead trees left in place may serve as a source for the disease to be vectored by beetles, sharpshooters and other pests to healthy nearby trees.  Remove dead or dying trees to prevent disease spread.

RDCS LLC Hired as Consulting Arborist by PCL Construction for UCSD Triton Pavilion Project

PCL Construction, is the general contractor managing the Triton Pavilion project at UC San Diego.  PCL Triton Pavilion.  The Triton Pavilion project includes developing a new, large student center and be a future major stop for the San Diego trolley Blue Line.  The trolley Blue line expansion to be completed in 2021 will connect downtown San Diego to University City. Union Tribune Article

To determine how to manage existing campus trees in conflict with future construction, PCL hired Rappoport Development Consulting Services LLC as a sub-consultant providing arboricultural consulting services.  Mr. Jeremy Rappoport, President of RDCS, will assess and tag all the project trees and develop a tree inventory.  The inventory will identify the tree, trunk diameter, crown height,  quantity, structure and health condition.  These metrics will assist in determining tree retention, protection, and relocation.

RDCS founder Jeremy Rappoport is an ISA certified arborist, tree risk assessor qualified, ASCA Registered Consulting Arborist (RCS #564), C-27 California Landscape Contractor #436000 and a professional horticulturist.  RDCS LLC provides arboriculture, landscape, horticulture and land development consulting services for civil engineers, landscape architects, prime contractors, municipalities, HOA’s, commercial and residential property owners and  expert witness litigation and support services for plaintiff and defendant attorneys and insurers.