The Four Biggest Threats to Trees Living in Southern California

In many ways, southern California is an ecological paradise. A wide variety of tree species thrives in the region’s warm climate, including everything from palm trees to redwoods to fig trees. Many homeowners and commercial property managers are keen to take advantage of this fact by planting a nice selection of trees.

However, while southern California is a welcoming habitat for those species well-suited for the local conditions, others will be unable to survive in the region. This means that proper species selection is crucial, as you’ll need to install trees that can withstand the challenges presented by the local environment.

Some of the most important threats facing trees in Long Beach, Beverly Hills, Los Angeles and the surrounding region are detailed below.

1. Drought

Like most other areas that experience a Mediterranean climate, southern California typically receives very little rainfall (if any at all) throughout the summer. While most native species — or those hailing from similar climates in other portions of the world – have evolved adaptations that enable them to withstand the long dry season, many exotics will struggle to survive without supplemental irrigation.

In addition to supplying plants with more water, you can also improve the drought tolerance of a tree by planting it in an area sheltered from the wind and the afternoon sun. Be sure to apply supplemental water on an infrequent, yet thorough basis, which will encourage deeper root development. This will help the tree access water locked deeper in the soil.

2. Wildfire

Wildfire is a perpetual threat for those living in most of California, and that includes the trees. Some of the native species, such as sequoias, have evolved exceptionally thick bark, which protects the delicate living tissues inside the trunk from the searing temperatures of a fire. Other native species have adapted their reproductive strategy to work in conjunction with the regular fire cycle. For example, many trees only release their seeds after exposure to fires. Because the fire has cleared out the vegetation beneath the tree, the new seedlings will not face the competition they normally would.

There isn’t much you can do to protect your trees from wildfire, except to select fire-adapted species and avoid planting them too close together, which will make it more difficult for the fire to jump from one tree to the next. Of course, you’ll also want to avoid planting trees in close proximity to your home, as they can serve as a way for the fire to reach your home.

3. Pollution

Southern California may be beautiful, but thanks to the dense population and thriving industrial sector, the region is one of the more polluted areas in the country. Trees actually help to counteract many of the problems caused by this pollution, such as absorbing harmful gases and reducing the amount of runoff water flowing across the land. However, in the process, many trees become stressed by the pollution and ultimately end up dying.

Fortunately, trees vary in their ability to cope with pollution, and some tend to thrive in polluted cities and suburbs. So, the best way to help ensure your trees don’t begin to suffer from the filth in the local air and water is by selecting a species that tolerates pollution and the urban life well.

4. Invasive Pests

California certainly doesn’t have a monopoly on problems associated with invasive species, but because of our region’s warm climate and the fact that many goods coming from all regions of the globe enter the country here, our local trees often suffer at the hands of introduced pests and pathogens. The Asian citrus psyllid, which is associated with the deadly citrus greening disease, is perhaps the most famous example, but plenty of others exist.

The best way to avoid problems with known invasive pests is by selecting species that are not vulnerable to the pests. Don’t, for example, decide to plant a row of orange trees in the middle of areas overrun with citrus psyllids. It is also possible in many cases to purchase cultivars of normally vulnerable species, which will not be harmed by the pest.

Despite the threats facing the trees of Long Beach, Santa Monica, Beverly Hills or anywhere else in the greater Los Angeles area, many obviously survive. But to give your trees the best chance of surviving, you’ll need to select those species and cultivars that can cope with the challenges common to our area.

If you need some help selecting trees that are likely to thrive in your property – or help to support the trees already planted there – contact your friends at Evergreen Arborist Consultants. We’d be happy to help provide actionable advice that will give your trees the best chance at living long, healthy lives.

Trees are no match for mother nature’s wind

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Winds were erratic throughout the day. In some places, they were like a breeze. In other areas they were so strong they knocked down trees as if they were toothpicks. In some cases, they dropped on top of homes. In others, they damaged sidewalks as the roots of large trees pulled out of the ground.
One big one landed on a freeway! A big eucalyptus landed on the 405 in the Irvine area causing a backup in traffic for awhile.

High winds made the drive on the 215 tension-filled for high profile vehicles drivers. The wind was so strong at one point it pushed an 18-wheeler over like a tinker toy in the Devore area.

Michael Green is an arborist. We looked at video after video of fallen trees and, for the most part, he felt the recent rains and the high winds were a fatal combination for some trees.

Said Green, “The heavy rains do play a role in that”… rain saturates the ground… loosens the soil.. and with winds “trees will topple over.”

So you can imagine how Keith Harvey felt when he saw that happen on top of his house! The one in Rancho Cucamonga. Harvey told us, “I was like, get our grandson. Get him up and get him out of there. When I got here just seeing a big old tree on the house I’m like … okay… wow!”

Michael Green says you may not have a “wow” moment if you maintain large trees around your home. He says, get them inspected from time to time,  “and pruned because…. with pruning the can reduce the weight of a tree if its too large you can do some pruning to mitigate it.”



Construction Trauma can Topple Trees

Coping with construction is the most challenging obstacle many trees will face in their lives. Given enough time to adapt, trees are extraordinary organisms that can withstand many environmental stresses; however, the rapid environmental changes wrought by construction occur too quickly for many trees to survive.

While some trees’ health may decline within days of construction-related stress, others seem to take the damage in stride.

Unfortunately, this is not always an accurate reflection of such a tree’s health, and many of these stoic specimens die a few years after construction takes place.

The only way to prevent large-scale tree losses during construction is by understanding the biology of trees and the types of stress that construction projects create. With adequate foresight and planning, many of these loses can be prevented. Additionally, by understanding which trees are unlikely to survive a given project, you can focus your conservation efforts where they are most effective.

Soil Compaction, Grade Changes and Root Health

A sample of soil is comprised of minerals, organic matter, innumerable microscopic organisms and small voids, called pores by botanists, geologists and others interested in such matters. Some of these pores hold water, while other pores contain air. These pores are very important for trees.

While the large roots flaring out from the trunks of trees anchor them to the ground, they do not absorb significant amounts of water or air. Trees leave this job to their many fine roots, located further from the trunk.

The problem occurs when construction activities compact the soil. This destroys the pores in the soil, preventing the trees from absorbing water and air. Additionally, if compacted enough, the tree’s roots can become trapped and unable to grow in a normal manner.

Many different construction activities compact the soil, such as preparing the foundation of the building, or simply the heavy vehicle traffic associated with construction projects. Even if efforts to prevent compacting the soil are taken, grade changes can just as easily doom trees.

The fine absorbing roots of trees primarily reside in the upper 12 inches of the soil. They penetrate this type of soil well, and are able to provide the tree with resources from a relatively wide area. However, when additional soil is placed over tree roots, it reduces their ability to survive. Grade lowering efforts often sever roots, which is as traumatic and destructive as it sounds.

Mechanical Trauma and Bark Damage

Perhaps the simplest and most obvious form of damage trees suffer from construction projects is mechanical damage to the trunk or major limbs.

Whether heavy equipment snaps part of a tree’s lower limbs, or laborers using hand tools rip large portions of bark from a tree’s trunk, the tree’s primary defense mechanism – the bark – is compromised, opening the tree up to a variety of pests and pathogens. If the cambium layer is affected, the wounds may be serious enough to kill the tree.

Some trees are more resilient than others are in the face of such indignities. Those trees with thick bark are better able to recover from damage to the trunk or major limbs than those with thin bark are.

With adequate tree protection zones in place, such damage is less likely to occur.

Sudden Succession

Trees that grow in the open often develop broad crowns and root systems that help them to withstand strong winds. Over time, many of these trees even produce wood in places that improves their ability to withstand the prevailing winds. However, trees that grow in forests — or where competition limits the spread of their canopy and roots — are more susceptible to windthrow.

Living inside the forest, this is rarely a problem, as the nearby trees partially block the wind. However, when trees along the edge of the forest are removed, it exposes the trees behind them.

These newly exposed trees are now at increased risk of failing, perpetuating the pattern of exposure and failure. In addition to increasing their susceptibility to blowing over, these formerly shaded trees may develop sunscald.

Preventative Steps

When considering any construction project that will take place near trees, you should secure the services of a skilled arborist to assess your trees and develop a tree protection plan. In many jurisdictions, such a plan is required before construction begins.

The arborist will help devise tree protection zones, consider the potential effects grade changes and predict how the trees will respond to changes in wind and water flow. Your arborist may also investigate the health of your existing trees to determine which measures – if any – are appropriate. For instance, trees may require supplemental watering or fertilization, prior to the onset of construction.

Dead branches should be pruned for safety’s sake, and structural pruning may be required to ensure the tree has the greatest chances of surviving the construction. Mulching is usually a good standard practice, but during construction activities, exceptionally thick mulch layers may be warranted.

camp tawonga sign

Pacific Gas & Electric Found Nothing Wrong With Deadly Tree

Yosemite National Park—This past summer, a 21-year-old lost her life and four adults were treated at hospitals after a tree fell at Camp Towanga near Yosemite National Park.  Pacific Gas & Electric Co. had recently inspected the tree in question and apparently found nothing wrong with the oak.  PG&E were required to inspect due to the presence of nearby power lines.  Tuolumne County sheriff’s spokesman Jim Oliver called the incident a “freak accident.”

Annais Rittenberg, 21, was in her second year as a camp counselor for Camp Towanga, a Jewish camp in Yosemite, when the tree fell on a campfire circle of which she was a part.  Fortunately, no children were injured, but Rittenberg lost her life and four other adults were hurt, two of whom had to be hospitalized. Read more

Pacific Palisades Tree Failure

In June 2006 in Pacific Palisades, a large carob tree fell over and crushed an unoccupied SUV. The street was closed while emergency crews cleared the street. A couple days later, a large limb off a eucalyptus tree fell a block from where the carob had failed. NazairoSauceda, from the Bureau of Street Services in the Public Works Department, commented on the tree failure, “We are investigating the tree that failed. They don’t fail like that typically.” The carob tree failed at the root ball and when it fell over, it totaled the SUV. Michael McRoskey, the owner of the SUV, said, “The scary part is if someone had been driving down that street around noon, they’d be dead.”

Tree failures are caused for a number of reasons, and each tree needs to be inspected individually for signs of over-weighted canopy, root damage due to construction, or overwatering and underwatering.

Before this incident, two other carob trees had failed at their roots and three other eucalyptus trees had shed large branches in Pacific Palisades. Residents have expressed concern over the potential hazards, but street tree superintendent Ron Lorenzen explained that there are about 700,000 street trees that are on a pruning schedule, but that the city only has funding to trim about a tenth of those trees each year. That means that the trees are on about a nine to ten year pruning schedule.

One local arborist commented that the city needs to have more funding up front for the care of the trees instead of having to pay legal expenses for damages once a tree fails.

Evergreen Arborists Consultants, Inc. has experience in examining thousands of trees. We evaluate a tree’s signs and symptoms ranging from decay, poor branch structure, poor pruning and maintenance practices, and roots.Please call us today for a consultation.

Sherman Oaks

Pine tree

Pine tree

An estimated 100-year-old pine tree in Sherman Oaks crashed into a family home early in the morning while the family was in residence. The owner of the house said it felt like an earthquake when the tree fell. No one was injured and both the family in the house and the neighbors living directly behind the house were evacuated. Los Angeles Fire Captain Steve Ruda said of the tree falling, “We’re lucky nobody was injured; the family managed to get out without any problems.” He added, “That is the thickest, heaviest pine tree I think I have ever seen.” Building inspectors have declared the house “unsafe” and they will need to decide when the family can move back into their house. In the meantime, power and water have been shut off to the house.   Evergreen Arborists Consultants, Inc. are tree specialists and tree experts who provide arboriculture and tree expert advice for tree roots, cutting tree roots, tree trunk damage, root damage, and damaged trees to Beverly Hills, West Hollywood, Brentwood, Los Angeles, Malibu, Palos Verdes, Encino, Sherman Oaks, and Laguna Beach. We specialize in conducting detailed investigations and providing independent analysis, as well as expert witness testimony in support of litigation. Please call us today for a consultation.

Hong Kong’s Heritage Trees are Failing

tree failure

tree failure

Hong Kong has removed many of its heritage trees in the past eight years due to typhoons and disease (the government’s definition of natural causes). Even with these removals, many trees are still failing and causing accidents. In August 2008 a coral tree that had a fungal infection fell in Stanley Market and killed a schoolgirl. In July 2012 another diseased heritage tree fell over in Park Lane Shopper’s Boulevard and injured five pedestrians.

The tree that fell in Park Lane Shopper’s Boulevard had brown root rot, and many other trees in the city are also becoming infected. The source of the infection is believed to be a dying banyan tree in Kowloon Park, and the spread of the disease has been through the air and the soil. Guidelines show that a tree infected with brown root rot should be burned and the soil replaced to keep the disease from spreading. Unfortunately, these guidelines aren’t adhered to for each tree that is being removed, and many believe this government negligence is increasing the problem.

Thirteen new trees have been added to the heritage list in the past few years to make up for the losses. The government lists heritage trees as old and valuable with the truck diameter greater than one meter, be of a rare species, be more than 100 years old, be of cultural or historical significance, or have an outstanding form.


Windstorm Damage



On December 18, 2012 people in Los Angeles and Ventura County suffered power outages from high winds. In all about 17,000 Southern California Edison customers were affected. Beverly Hills reported winds of 45 mph, and in Malibu, Saugus, and Newhall Pass the winds were approximately 50 mph. The winds caused a tree to fall on a pickup truck in downtown Los Angeles. There were no injuries.


Coral Tree Falls on San Vicente Boulevard

A large coral tree fell onto San Vicente Boulevard in Brentwood. The Chair of the Brentwood Community Council Board, Nancy Freedman, said that the tree is No. 15 in median No.3 at the corner of San Vicente Boulevard and Gorham Avenue. Coral trees are extremely drought tolerant and in an email Freedman noted that she had observed a pool of water from the sprinkler system next to the fallen tree, which may have contributed to the tree’s fall. Coral trees are prone to failure from wet conditions and over-watering. This is not the first tree to fall on this median and there are continuing efforts to maintain these trees.


Sycamores Downed in Malibu

Old tree

An old tree

California State Parks, working on the Malibu Lagoon overhaul project to replace non-native vegetation with native vegetation, uprooted seven 30-year-old sycamores during bulldozing. The bulldozer was removing vegetation through a process called “grubbing” and downed the trees. Suzanne Goode, senior environmental scientist for State Parks, said the sycamores would be reused within the project. “About three of them are going to be put in the bottom of the lagoon for fish habitat and to create a little roosting area for birds. A couple of them are going to be turned into benches for the park for the amphitheater.”

Some Malibu residents actively oppose the overhaul project, protesting the impact the bulldozing has on animals, fish, and other wildlife in the lagoon.

Evergreen Arborists Consultants, Inc. understands the requirements for arborist reports and protecting potentially impacted trees. Our arborists provide guidance throughout the construction process. This includes the protection of trees before construction, monitoring the trees during construction, and following up on the tree health after construction. Please call us today for a consultation.