Why keeping one mature street tree is far better for humans and nature than planting lots of new ones

Good for both the environment and human wellbeing. Credit: Willy Barton/shutterstock

by Mary Gagen,

Thanks to Victorian street planners, many British streets were designed to be full of big trees and, with 84% of the population living in urban areas, most people are more likely to encounter trees in the streets than they are in forests.

The UK is one of the least densely wooded countries in Europe (at 13% coverage compared to the EU average of 38%) and, as such, its are even more valuable.

This became all too clear as the UK first entered lockdown in spring 2020, when many people spent more time on their local streets and in parks. Online tree app Tree Talk saw a 50-fold increase in users as people fell in love with their local “ .”

They were quite right to do so. The wood of street trees stores carbon, while their roots and crowns support wildlife and slow rainfall, reducing urban flooding. Transpiration and shade from their canopies reduces temperatures in heatwaves, while pollution-trapping leaves lower the prevalence of asthma.

If these ecosystem services weren’t enough, having trees on our streets reduces crime rates and improves mental health and wellbeing. One mature street tree can have a net ecosystem service value of thousands of pounds.

Big trees are being felled

Sadly, the UK has an unhealthy street tree-felling habit. Up to 60 trees per day are chopped down to make way for buildings and infrastructure, such as roads or sewers. Felling rates could also rise as development accelerates and governments relax planning rules to aid post-pandemic economic recovery.

It is larger street trees which are most often the victims of development because they are a challenge for .

Large species like London planes, beech and oak need expensive, carefully engineered tree pits to help them grow safely surrounded by concrete and to prevent their roots from pushing up pavements. Such costs are more than offset, though, when we value nature—a single mature oak produces hundreds of thousands of liters of oxygen per year and supports thousands of species of birds, insects, lichen and fungus.

Residents and councils regularly clash over urban tree-felling. However, when Sheffield City Council entered into a contractor program a few years ago, which felled more than 5,000 trees, the protests made international news.

Councils are wary of street tree issues now, and often try to manage PR by claiming felling is mitigated by planting several smaller trees to replace each large one removed. When local authorities like Swansea City Council claim development will result in “more trees” they are of course right, but it is not the full story.

Just as any child would understand they were being ripped off if given a 2p piece and a 1p piece to replace a pound coin, removing large species trees and replacing them with small ones results in a net loss of ecosystem services.

Joe Coles, the urban tree campaigner responsible for conservation charity Woodland Trust’s work in Sheffield, describes this as a form of greenwashing. “If we value green infrastructure to the same level as gray then large street trees will become far too valuable to lose,” he tells me. “Until there is acceptance that large trees, taking decades to reach maturity, have significant value—a fact based on scientific evidence—we will continue to see spurious but convenient assertions that higher numbers of small replacement trees are adequate compensation to facilitate development.”

Size really matters with trees. The annual net ecological benefit of planting a large species tree is 92% greater than planting a small one. Mature street trees do everything from having a positive effect on infant birth weight in lower socio-economic demographics, to increasing resilience to major life events among people who live within sight of them. Consumers spend more on streets that are lined with large trees.

Large street trees are the most valuable green infrastructure asset cities have and when that value is overlooked, disasters happen. Even winning the UK’s “tree of the year” competition in 2020 couldn’t save Hackney’s Happy Man Tree from being felled in 2021 to make way for a new housing development.

More than 25,000 petitioners objected to the removal of the healthy, 150-year-old London plane, with even the developers admitting it would have been avoidable had earlier consultation taken place.

There is hope for change in the form of tree strategies which set policies to guide development and planning and which require community consultation. They are a valuable tool for stewarding urban trees for future generations.

Bristol, perhaps the UK’s flagship green city, has adopted a tree replacement standard to ensure planting new trees meaningfully offsets the loss of carbon and ecosystem services where felling cannot be avoided. Tree replacement standards ensure an adequate number of trees are planted to offset each lost and quantifies the financial contribution developers must make if they choose to fell.

Even tree-war epicenter Sheffield has moved forwards, bringing people together to develop a new street tree partnership working strategy that values street trees for the benefits they bring to people, the city and the environment.

These strategies allow local authorities to mandate that developers value tree size and the total canopy cover in a city. The idea is to prevent the use of “stem counts” to hide the removal of large trees and their replacement with smaller trees that are less valuable in terms of carbon storage, ecosystem services and even human wellbeing.

This article is republished from The Conversation under a Creative Commons license. Read the original article.


How Oak Trees Evolved to Rule the Forests of the Northern Hemisphere

Aangel oak, a southern live oak located on Johns Island, S.C., is an estimated 400 to 500 years old.
Credit: Dawna Moore Alamy

Genomes and fossils reveal their remarkable evolutionary history

  • Oak trees are highly diverse and widespread, and they are keystone species in the forests they inhabit.
  • Advances in genomics have allowed researchers to reconstruct the evolutionary history of oaks.
  • The findings will have implications for managing oaks to ensure their survival as the planet warms.

AUTHORS

Andrew L. Hipp is a senior scientist and herbarium director at the Morton Arboretum in Lisle, Ill. His research addresses the evolution, maintenance and implications of plant diversity, with a focus on the phylogenomics of oaks. Credit: Nick Higgins

Paul S. Manos is a professor at Duke University. He studies the systematics and biogeography of the flowering plants, with a particular focus on the evolution of oaks, hickories and walnuts. Credit: Nick Higgins

Jeannine Cavender-Bares is a professor at the University of Minnesota. She studies the origins, physiological function, and organization of plant biodiversity and their consequences, with an emphasis on oaks. Credit: Nick Higgins

 

If you were dropped into virtually any region of North America 56 million years ago, you probably would not recognize where you had landed. Back then, at the dawn of the Eocene epoch, the earth was warmer and wetter than it is today. A sea had just closed up in the middle of the Great Plains, and the Rocky Mountains had not yet attained their full height. The continent’s plant and animal communities were dramatically different. In the Canadian High Arctic, which today harbors relatively few tundra plant species, year-round temperatures above freezing nurtured a rich and diverse flora; Ellesmere Island in far northern Canada, across from the northwestern coast of Greenland, was home to alligators and giant tortoises. What is now the southeastern U.S. was dominated by tropical rain forest, complete with primates. The northeastern U.S., for its part, ranged from broad-leaved (as opposed to needle-leaved) evergreen forest to deciduous forests of ginkgo, viburnum, birch and elm, among other species. The deciduous broad-leaved forests that now cover 11 percent of North America north of Mexico were in their infancy. But that was about to change, with the spread and extraordinary diversification of what would eventually become some of the most ecologically and economically significant woody plants in the world: the acorn-bearing, wind-pollinated trees we call oaks.

Over the course of some 56 million years, oaks, which all belong to the genus Quercus, evolved from a single undifferentiated population into the roughly 435 species found today on five continents, ranging from Canada to Colombia and from Norway to Borneo. Oaks are keystone species, foundational to the functioning of the forests they form across the Northern Hemisphere. They foster diversity of organisms across the tree of life, from fungi to wasps, birds and mammals. They help clean the air, sequestering carbon dioxide and absorbing atmospheric pollutants. And they have shaped human culture, feeding us with their acorns and providing wood to build our homes, furniture and ships. Indeed, oaks have proved so valuable to people that we have immortalized them in legends and myths for centuries.

Oaks are especially prominent in the Americas. Approximately 60 percent of all Quercus species live here. This astounding variety, along with the fact that the oaks in this region account for more forest tree biomass than any other woody plant genus in North America and Mexico, makes them the single most important group of trees in the continent’s forests. To understand forests, then—their biodiversity, food webs and contributions to human well-being—one must understand how oaks came to rule them. For decades scientists could only speculate about much of the evolutionary history of oaks because of gaps in their fossil record and limitations of the biomolecular techniques used to infer evolutionary events from the DNA of living organisms. But recent advances in genome sequencing and analysis have allowed us and our colleagues to reconstruct a detailed picture of the origin, diversification and dispersal of oaks. It is a remarkable evolutionary success story, one that will have important implications for predicting how these essential trees will fare in the face of climate change—and for developing management plans to ensure their survival.

Red and White

The differences between major groups of oaks are readily apparent to even a casual observer. In the Americas, oaks are dominated by two evolutionary lineages that you may already know. One of these, the red oak group, is composed of species with bristle-tipped leaves. In most red oak group species, pollen takes a full year from the time it lands on the female flower to fertilize the seed, so that acorns—the fruits of these trees—pollinated in one year only ripen in the next. Species in the other major lineage, the white oak group, have no bristles on their leaves, and the leaves generally contain more soil-enriching nutrients when they fall than those of red oaks do. Also, white oak acorns almost all ripen the same year they are pollinated, sometimes germinating before they even fall. Gray squirrels preferentially cache red oak acorns to eat at a later date because they are less likely than white oak acorns to go bad before the squirrels can get back to them.

White oaks are also able to efficiently plug the water-conducting, tubelike cells called vessels in their wood with tyloses, balloonlike structures that seal the vessels as a barrier against deadly fungal diseases such as oak wilt. Red oaks are slower and sloppy in their defense. Consequently, white oaks have long served as wood for ships and wine barrels because the plugged vessels of the white oak species hold water more effectively than those of the red oaks. Chewing insects recognize the differences between red and white oaks, and most are adapted to favor either one or the other of these two groups. Even mycorrhizal fungi, which connect plant roots to soil nutrients, appear to recognize the differences between the two types of oaks: many favor symbiotic relationships with species in one lineage over the other.

When we get to the species level, however, closely related oaks are often difficult to tell apart. The variation within species, the result of both plastic responses of the trees to their environment and genetic variation between individuals, often appears to be as great as the variation between species. And oaks hybridize commonly within their group, be it the white or red lineages or any of the six other major lineages of oaks worldwide. These two factors—high variation within species and ongoing hybridization between species—complicate classification.

Hybridization can also make it difficult to reconstruct the evolutionary history of oaks using traditional biomolecular techniques, which involve sequencing one or a few genes, because individual genes often trace different histories. Moreover, a single oak species may have hybridized with numerous different species, so that different genes record different aspects of this history across the geographical range of the species. The oak genome is thus a mosaic shaped by speciation and hybridization. The sequences of only one or a few genes cannot reveal the full history of speciation in oaks.

Two decades ago researchers had only the sequences of DNA from chloroplasts—the cell organelles that carry out photosynthesis—and a few nuclear genes to go on. It was enough to discern the overall branching structure of the oak tree of life, but we could not see the arrangement of its endmost branches. In 2008 the three of us realized that new molecular techniques we were already using to study hybridization and the limits of species in the red oak group might also enable us to infer oak evolutionary history. Since then, we, in collaboration with colleagues around the world, have employed an approach called restriction-site associated DNA sequencing to read short regions of DNA from across the genome. We analyze these data using statistical methods that reconstruct the order in which species have branched from common ancestors and which ones have hybridized since that divergence. By marrying these analyses to fossil data, we can estimate the maximum ages of key events in oak evolutionary history. Despite the complex genetic history of oaks, we have been able to deduce much of the history of speciation in this group going back to the root of the oak tree of life.

Red oaks

Red oaks have bristle-tipped leaves (top); the leaves of white oaks lack bristles (bottom). Credit: John Seiler Getty Images (top); Getty Images (bottom)

Southward Bound

We may never know precisely when or where the very first oaks arose, but roughly 56 million years ago a population of oaks growing near what is now Salzburg, Austria, left in the mud a bit of the massive amount of pollen they produced each spring. These pollen grains, which are shaped like a rugby ball with three grooves running lengthwise and with surface textures that vary by lineage, are the earliest unambiguous fossil evidence of oaks on record. Throughout the early Eocene, land bridges spanning the Atlantic and Pacific Oceans connected North America and Eurasia. Plants and animals freely crossed between the two continents. Oaks were most likely part of a vast forest that spread across the continents of North America, Europe and Asia. This makes it difficult to say with any confidence whether oaks originated in Eurasia and sent a branch off to the Americas, or vice versa. The better answer to where modern oaks arose may simply be “in the north.”

In any case, remarkably soon after they arose, oaks started to separate into two major branches: one limited to Europe, Asia and North Africa and the other largely limited to the Americas. The separation between continents was imperfect at first. For example, the oldest fossil attributable to the ring-cupped oaks, based on the concentric rings formed by the woody scales on its acorn cap, was deposited in Oregon around 48 million years ago. Today this lineage is restricted to Southeast Asia. And red oaks, which today are an American group, have been reported from fossil sites in Europe dating to some 35 million years ago. But when global temperatures started their long descent about 52 million years ago, oaks were gradually pushed southward, away from the land bridges that have connected Eurasia and North America intermittently over the past 50 million years. As cooling drove northern oak populations extinct, the divisions between the two continents became very clean, with no species from the Eurasian clade showing up in the Americas and only two branches of the American clade showing up in Eurasia.

Before they could be pushed too far to the south, oaks were further subdivided into the eight major lineages we recognize in modern forests. Three of them are restricted to the Americas: the red, golden cup and southern live oaks. One lineage, that of the white oaks, originated and diversified in the Americas but sent an offshoot back to Eurasia. We know these major lineages arose early in oak evolution because one of the oldest American oak fossils is a 45-million-year-old white oak from Axel Heiberg Island in Nunavut, Canada, that can be distinguished from the red oaks and all other major lineages of oaks. But fossils from this initial phase of diversification are hard to assign to any one lineage, so we rely on molecular data to estimate when the other oaks separated into independent lineages. The integration of molecular data with selected fossils indicates that the world’s eight lineages split early on. It is an important part of the story because it explains what happened next as the North American oaks underwent their own burst of diversification.

Lands of Opportunity

As temperatures cooled worldwide, the North American climate also became more seasonal. The Rocky Mountains were continuing to rise, and their rain shadow dried out the Great Plains. The tropical forests and broad-leaved evergreen forests that had flourished across North America were gradually restricted in range and driven to extinction by around 40 million years ago. Oak pollen and leaf impressions became more common in the North American fossil record 35 million years ago, by which time decreased temperatures and increased seasonality had converted North America north of Mexico from a mostly tropical to a mostly temperate continental landscape. As climate change extirpated tropical forests from North America, ecological opportunity arose for the oaks.

The red and white oaks moved south into this newly opened territory, each splitting into a lineage on the western side of the Rocky Mountains that gave rise to the modern-day oaks of California and the Pacific Northwest and into a lineage on the eastern side of the Rockies that gave rise to the oaks of eastern North America. Within the latter region, each of these major oak groups subdivided into a predominantly northeastern lineage, a predominantly southeastern lineage and a primarily Texan lineage. From eastern North America, perhaps by way of Texas, the red and white oaks then moved into Mexico between 10 million and 20 million years ago.

In all these areas, palms and broad-leaved evergreen trees had been pushed south or driven partially or wholly extinct by the cooling and increasingly fluctuating climate. The resulting abundance of open habitat enabled oaks to diversify. Increased ecological opportunity allowed oaks to undergo an adaptive radiation, in which nascent species rapidly fill spaces that other species are not occupying. In doing so, these young populations became more ecologically distinct from one another, thereby limiting the movement of genes between them. They became reproductively isolated, so that genes moved less between separated populations than among trees within populations. Subsequently, new genetic mutations and rearrangements could accumulate that distinguished the populations from one another. Through this process, they became new species.

This adaptive radiation played out most dramatically in Mexico and Central America, where about 40 percent of all the world’s oaks reside. Recall that oaks were a largely cold-adapted lineage that spread across the continent as temperatures dropped and seasonality increased. As they migrated south into Mexico, oaks climbed to higher elevations that more closely resembled the temperate biome in which they had evolved, and they encountered high topographic variation that readily separated them into reproductively isolated populations. Oaks also evolved more rapidly along the continuum from low water availability to high water availability as they moved into Mexico. Tacking up and down the mountains, different populations adapted to different levels of drought. This ecological differentiation most likely worked hand in hand with increased physical separation to promote reproductive isolation between populations.

Thus, the reason for the high oak diversity in Mexico appears not to be warmer temperatures. And because Mexican oaks are relatively young, their high diversity has not accrued over comparatively long periods of evolutionary time. Rather adaptive radiation led to higher speciation rates in these evolutionarily young Mexican oaks as they moved into the mountains. This change suggests that if oaks had been suited to climb into the Rockies and flourish there—that is, if they could have survived the combination of short growing seasons and cold winters of the northern mountains—they might have developed high diversity in this region as well. Their evolutionary heritage simply did not equip them for these extremely harsh environments. Only a lone white oak species, the Gambel oak (Quercus gambelii), even comes close, and that species is limited to the southern Rockies.

The oaks were finally stopped in their march southward, perhaps by dramatic reduction in seasonality or strong competition from tropical forest species, only barely making it across the Isthmus of Panama into the north of South America. Yet this is not the whole story. The oaks’ southward journey actually played out twice, simultaneously and in the same places. Because white and red oaks had already separated from each other by the time they started moving south, this diversification history happened in parallel in both the red and white oaks. Two distinct but very closely related lineages, not one, traced the biogeographical history we just described: moving south, splitting around the Rocky Mountains, heading into Mexico from an eastern North American ancestor. This history may explain part of the species richness and abundance of oaks in the Americas. They essentially double-dipped as they ventured south.

Fossil acorn

Fossil acorn from Oregon dates to the Eocene epoch. Credit: Thomas J. Bones 

Good Neighbors

One of the most exciting areas of our research has been the integration of a genome-level understanding of the oak tree of life with physiological studies of oak adaptation to climate and habitat and community studies of oak forest structure. As oaks spread south and diversified in different regions, the white and the red oaks encountered similar habitats and repeatedly solved the same ecological problems in novel ways. As a result, we often find red and white oaks growing together in the same habitats. For example, on poor rocky soils and bluffs in the eastern U.S., you can find the white oak Quercus stellata, also known as the post oak, growing next to the red oak Quercus marilandica, commonly called the blackjack oak. In the mountains of southern Arizona, the iconic white oak Quercus arizonica often grows beside the red oak Quercus emoryi.

This pattern of oak co-occurrence is found in wooded plant communities across much of the country, and it has another intriguing feature. Whereas distantly related oaks tend to grow together, closely related oaks within lineages tend not to be found together. Along an elevational gradient in the Chiricahua Mountains of southern Arizona, for example, white oak species pass the baton as you walk upslope, transitioning broadly from one to the next as you hike uphill, and red oak species do as well. In the lowlands of Florida, white oak species separate across the sandhill, scrub and ravine habitats shaped by karst topography and fire. Red oaks do the same.

What shapes this pattern of oak co-occurrence? Ecological differentiation within the red and white oaks is influenced in part by the fact that no single species is able to master every habitat. Instead species tend to specialize on a limited part of the available ecological space. In oaks, physiological trade-offs within each lineage subdivide habitat and climatic space so that close relatives are less likely to co-occur. In the Chiricahua Mountains, for instance, drought adaptation separates close relatives along the elevation gradient. Species living near the bottom of the mountain are particularly good at avoiding drought, dropping their leaves during dry seasons. Species living at higher elevation, where there is more overall moisture, focus on surviving daily fluctuations in water availability by allowing leaf water content to drop lower before they suffer damage.

In contrast, in Florida, which is comparatively flat, soil moisture availability and fire intensity structure oak communities. Closely related species in these communities show trade-offs between growth rate and drought tolerance along moisture gradients and between bark thickness and the ability to reproduce via underground stems along gradients of fire intensity. In both regions, and indeed across the country, parallel trade-offs are found in both red and white oaks, and trees with convergent traits from the two lineages tend to grow together.

Members of different lineages may co-exist well with one another in each habitat because they differ in their susceptibility to disease: proximity to a more distantly related neighbor may be less likely to result in an epidemic because red and white oaks tend not to spread the same diseases. There is even evidence that oaks help one another get established and persist by creating a soil environment that benefits the mycorrhizal fungi they need to acquire nutrients. Then, once a forest has become established, oaks become dominant and prevent other kinds of trees from setting up shop. Our work makes clear that the evolutionary origins of oaks shape the complex ecological interactions that help to explain why the trees are so abundant and diverse in North America. The tree of life casts its shadow across the structure of our oak forests.

Creative Hybridization

Now that we can delineate the branching history of the oak tree of life in some detail, the trees’ propensity to hybridize has become all the more interesting. People often think of hybridization as a destructive force, eroding genetic differences between species. Yet oaks form what is called a syngameon, in which ecologically and physically distinctive species persist in spite of ongoing gene flow. It has long been hypothesized that genes migrating between species of the syngameon might help oaks adapt to novel environments. Could, for example, genes that contribute to drought adaptation in the post oak migrate into the bur oak (Quercus macrocarpa) in the southern regions, where they co-occur, and help the bur oak adapt to the drying conditions it is expected to encounter under global warming? We know already that there is localized gene flow between oak species and that species differ in what genes they exchange depending on where on the landscape they are, what species they co-occur with, and the climate and habitat in which the trees are growing. We also know that after genes move from one species into the other, they can move beyond the range of the species in which they arose, apparently propelled by environmental selection. These examples suggest that adaptive gene flow may play an important role in oak evolution. We are on the cusp of the integrative genomic and ecological studies needed to understand this process in depth.

We would still like to know what genes and attributes—flowering time, habitat preference, geographical distance—drive speciation in oaks and whether ecological differences evolve while populations are growing together or only when they are separated. We are close to understanding what genes shape differentiation. Recent work in European oaks shows that genes influencing both their ability to cross-pollinate and their ecological preferences (for instance, tolerance of drought, cold and disease) are involved in species differentiation. Yet these findings only tell us that ecological differences evolve in species, not that they drive species differences. Statistical analyses that simulate alternative speciation histories suggest that in a group of four widespread European white oaks that hybridize today, the genomic differences between the species arose when the species were born in different geographical areas, with opportunities for gene flow arising only after the fully formed species migrated back into contact with each other. Still, the high degree of species co-occurrence in the American oaks raises the question of whether hybridization contributed to their diversity.

A firm grasp of when, where and how oaks came to be so diverse is crucial to understanding how oaks will resist and adapt to rapidly changing environments. Oaks migrated rapidly as continental glaciers receded starting around 20,000 years ago, and hybridization between species appears to have been key to their rapid response. The insights we can gain from elucidating the adaptive benefits of gene flow are critical to predicting how resilient oaks may be as climate change exposes them to fungal and insect diseases with which they did not evolve. As insects that transport pathogenic fungi increase their ranges and change their patterns of reproduction with earlier springs, oaks may have trouble holding their ground unless they can evolve quickly enough to resist diseases they have never before encountered. Our challenge for the coming decade as plant biodiversity scientists will be to figure out how differentiation between species and movement of genes between those species will influence the trajectory of oak evolution and population persistence. If we understand these processes well enough, we stand a chance of using that knowledge to predict what our forests will look like a century or more from now. Perhaps it can guide our plans to manage longer-term survival of the vital oaks.

This article was originally published with the title “Ascent of the Oaks” in Scientific American 323, 2, 42-49 (August 2020)

US cities are losing 36 million trees a year. Here’s why it matters and how you can stop it

If you’re looking for a reason to care about tree loss, this summer’s record-breaking heat waves might be it. Trees can lower summer daytime temperatures by as much as 10 degrees Fahrenheit, according to a recent study.

But tree cover in US cities is shrinking. A study published last year by the US Forest Service found that we lost 36 million trees annually from urban and rural communities over a five-year period. That’s a 1% drop from 2009 to 2014.

If we continue on this path, “cities will become warmer, more polluted and generally more unhealthy for inhabitants,” said David Nowak, a senior US Forest Service scientist and co-author of the study.

Nowak says there are many reasons our tree canopy is declining, including hurricanes, tornadoes, fires, insects and disease. But the one reason for tree loss that humans can control is sensible development.

“We see the tree cover being swapped out for impervious cover, which means when we look at the photographs, what was there is now replaced with a parking lot or a building,” Nowak said.

More than 80% of the US population lives in urban areas, and most Americans live in forested regions along the East and West coasts, Nowak says.

“Every time we put a road down, we put a building and we cut a tree or add a tree, it not only affects that site, it affects the region.”

The study placed a value on tree loss based on trees’ role in air pollution removal and energy conservation.

The lost value amounted to $96 million a year.

Nowak lists 10 benefits trees provide to society:

Heat reduction: Trees provide shade for homes, office buildings, parks and roadways, cooling surface temperatures. They also take in and evaporate water, cooling the air around them. “Just walk in the shade of a tree on a hot day. You can’t get that from grass,” Nowak said. To get the full temperature benefit, tree canopy cover should exceed 40% of the area to be cooled, according to a recent study in the Proceedings of the National Academy of Sciences. “A single city block would need to be nearly half-covered by a leafy green network of branches and leaves,” the authors wrote.

Air pollution reduction: Trees absorb carbon and remove pollutants from the atmosphere.

Energy emissions reduction: Trees reduce energy costs by $4 billion a year, according to Nowak’s study. “The shading of those trees on buildings reduce your air conditioning costs. Take those trees away; now your buildings are heating up, you’re running your air conditioning more, and you’re burning more fuel from the power plants, so the pollution and emissions go up.”

Water quality improvement: Trees act as water filters, taking in dirty surface water and absorbing nitrogen and phosphorus into the soil.

Flooding reduction: Trees reduce flooding by absorbing water and reducing runoff into streams.

Noise reduction: Trees can deflect sound, one reason you’ll see them lining highways, along fences and between roads and neighborhoods. They can also add sound through birds chirping and wind blowing through leaves, noises that have shown psychological benefits.

Protection from UV radiation: Trees absorb 96% of ultraviolet radiation, Nowak says.

Improved aesthetics: Ask any real estate agent, architect or city planner: Trees and leaf cover improve the looks and value of any property.

Improved human health: Many studies have found connections between exposure to nature and better mental and physical health. Some hospitals have added tree views and plantings for patients as a result of these studies. Doctors are even prescribing walks in nature for children and families due to evidence that nature exposure lowers blood pressure and stress hormones. And studies have associated living near green areas with lower death rates.

Wildlife habitat: Birds rely on trees for shelter, food and nesting. Worldwide, forests provide for a huge diversity of animal life.

Planning for trees

Nowak says there’s a downside to trees too, such as pollen allergies or large falling branches in storms, “and people don’t like raking leaves.” But, he says, there are ways cities and counties can manage trees to help communities thrive. “You can’t just say ‘we’re not going to have forests.’ We might as well manage and work with the trees.”

“You don’t want a tree in the middle of a baseball field. It’s very difficult to play sports if you have trees in the way. Or trees in the middle of freeways.”

Nowak says we can design and manage tree canopies in our cities to help “affect the air, to affect the water, to affect our well-being.”

Urban forests especially need our help to replace fallen trees. Unlike rural areas, it is very difficult for trees to repopulate themselves in a city environment with so much pavement and asphalt.

“A lot of our native trees can’t actually find a place to drop an acorn so they can regenerate,” explains Greg Levine, co-executive director for Trees Atlanta.

“That’s why the community has to go in and actually plant a tree because the areas just aren’t natural anymore.”

The job is not complete when the saplings take root. Organizations like Trees Atlanta and their volunteers plan most of their year to care for these young trees until they’re mature enough to thrive on their own.

“We try to prune trees for 10 years to make sure they get a good healthy structure.” Levine adds. “We also add mulch around trees to help keep the moisture in the ground so the tree doesn’t dry up. We have to have a lot of patience with planting trees around pavement, making sure that they can rise to the challenge. “

How you can help stop tree loss

Protect what you have: Nowak says the first step is caring for the trees on your own property. “We think we pay for our house, and so we must maintain it. But because we don’t pay for nature, we don’t need to. And that’s not necessarily true.”

Prune the dead limbs out of your trees: If they’re small enough, do it yourself or hire a company. The risk of limbs damaging your house is significantly lowered when there’s tree upkeep, Nowak said.

Notice where your trees may be in trouble: Often, you can observe when something’s wrong, such as when branches are losing leaves and breaking or when mushrooms are growing at the base or on the trees. You can also hire an arborist or tree canopy expert to assess the health of your trees on an annual basis. Or you can contact your local agricultural extension office for advice.

Don’t remove old trees if it’s not necessary: Instead, try taking smaller actions like removing branches. “It takes a long time for these big trees to get big: 50 to 100 years. And once they’re established, they can live a long time. But taking a big tree out and saying ‘we’ll replant,’ there’s no guarantee small trees will make it, and it will take a very long time to grow.”

Allow trees to grow on your property: Although everyone’s aesthetic is different, it’s the cheap way to get cooler yards and lower energy bills. It’s also an inexpensive approach to flood and noise control.

Nowak says he laughs when his neighbors wonder why their property doesn’t have more trees, because “I hear people running their lawn mowers.” Fallen seeds need a chance to implant, and constant mowing prevents that. If you don’t like where a seedling is growing, you can dig it up and plant it or a new tree where you like.

Educate yourself about trees and get involved: Many cities have tree ordinances that seek to protect very old, significant trees. You can get involved by attending city council meetings. You can also help your city plant trees by joining local nonprofit groups.

Volunteer or donate to tree planting and research organizations:

Seeing the Forest for the Trees: Southern California Edison and Your Property

By Zev Blumenfeld, Reporter | Posted: Thursday, March 12, 2020 9:00 am

© 2020 Mountain News

In December of 2019, a crew of contractors from ACRT Inc., an independent vegetation management company, arrived in the Upper Little Bear Mountain Club community. They walked the narrow, single-lane roads quintessential to the neighborhood, occasionally stopping to tie orange ribbons to select trees. A resident from the community, who wished remain anonymous, said he approached the contractors and inquired about the tags. But instead of receiving a clear answer, the man was given a telephone number to call.

These contractors were hired by Southern California Edison to assess potentially hazardous trees as part of the utility’s ongoing wildfire mitigation effort — an effort Edison claims will reduce the risk of a catastrophic fire.


Certified Arborist Rebecca Latta … has worked as an arboricultural, horticultural, water management consultant in the Los Angeles area for over 25 years, eight of which she said were as an Edison subcontractor.


But some homeowners question the aggressive approach Edison is taking within the mountain communities. Healthy trees have undergone tree topping, side pruning and in some cases have been cut down altogether.

Some affected property owners believe the contractors responsible for making these decisions lack the botanical expertise necessary to accurately assess the tree’s risk.

Additionally, Edison stated that they use arborists from out of the area, bringing into question whether their hires possess the knowledge of plants and wildlife specific to the San Bernardino Mountains.

Homeowners have expressed concern over the seemingly subjective criteria Edison and its contractors use when determining which trees need to be felled and which will remain standing — dependent more upon how the contractor feels on the day they scout a property rather than on a set of scientific criteria.

Meanwhile, Edison has tried to reassure the community that their vegetation management practices are ultimately in the best interest of public safety and fire prevention. 

The homeowner in the Upper Little Bear community is currently challenging the decision contractors made about a white fir tree in the community’s communal area. While this tree is not on his personal property, he believes that it is a financial asset to the community.

“The reason you come up here is for the trees,” he said. “This sets a bad precedent. It gives Edison a precedent to cut whatever and wherever they want.”

Certified Arborist Rebecca Latta conducted an independent assessment of the white fir on Feb. 27. Latta has worked as an arboricultural, horticultural, water management consultant in the Los Angeles area for over 25 years, eight of which she said were as an Edison subcontractor.

While evaluating, Latta estimated the white fir to be between 150 and 200 years old. She pointed to its damaged bark, noting that the edges of it were growing back.

“It looks like the tree is trying to put new wood on at the edges where the damage is, which means the tree has vigor,” Latta said.

She dismissed the idea that eyeballing the tree was a thorough enough analysis, instead insisting that Edison contractors should have used a sonic tomograph — a non-invasive machine that measures the thickness of the tree using soundwaves — to accurately determine if the internal wood is rotting.

She also noted four woodpecker holes located towards the middle of the trunk, indicating the tree’s potential to house wildlife, especially since the tree is in a wildlife corridor.

Edison and ACRT Inc.’s arborists had a different opinion.

“There are multiple wounds and cavities that have a high probability of causing tree failure,” stated Edison spokesperson Mary Ann Milbourn. “In the case of potential wildlife habitat, the arborist would flag it for environmental review. That was not the case with this tree.”

The fir sits adjacent to the man’s home and approximately 50 ft. from electrical lines — just out of reach if it fell, according to Latta’s estimate. In his yard, a tree as tall as the fir stands. It is about ten feet from the electrical lines, yet Edison’s contractors did not flag it for felling.

A Sliding Scale

The discrepancy between the assessments performed by Latta and Edison speaks to the seemingly arbitrary criteria, as well as the contrasting interests between the two parties. Latta says she is interested in environmental preservation while Edison’s Government Relations Manager Jennifer Cusack said that Edison errs on the side of caution — if there is even a slight chance that the tree will be a hazard then it will be pruned or felled.

Mountain resident Karla Kellems experienced these subjective criteria firsthand. “My husband was out working in the yard and an SCE (Edison) guy comes by,” Kellems said. Her husband was initially told that their trees would not need any management work done. But to her surprise, she said she later found an Edison door hanger on her front door. The hanger stated that her trees would be pruned. Kellems said she called the telephone number written on the door hanger and requested a re-evaluation. She spoke with the man who had left the hanger. When she asked if he was an arborist, he said “no,” but he was studying to become one. When the new arborist visited, Kellems said she was told no action would be necessary. “Had we not said anything, they would have pruned our trees,” she continued.

Edison maintains that their crews use a “tree risk assessment” for every tree. Milbourn said Edison and its contractors look at structural defects, decay, soil conditions and hazards the tree may pose. However, the Upper Little Bear Mountain resident said that he observed “no checklist whatsoever.”

“We’re going to always look for weak attachments, including bark,” said David Guzman, a Manager of Vegetation Management and Forestry at Edison.

They look for things like included bark, codominant leaders — areas where a trunk splits into two — less than eight feet from the ground, uprooting and the wind patterns. Guzman stressed that every arborist conducting a hazard tree removal assessment considers these qualities.

“They should be doing a tree risk analysis, and the person who should be doing that is somebody who has been trained as a tree risk assessor,” Latta said.

Qualified V.S. Certified

Edison has two vegetation management programs — a hazard tree management program and the distribution and transmission vegetation management plans. The former includes heavy tree topping and removal. The latter focuses on trimming for compliance and possible removal.

According to “Revision 2” of their “2020-2022 Wildfire Mitigation Plan,” the utility plans to assess and perform prescribed mitigation to 75,000 trees under its hazard tree management program in 2020. Guzman said that Edison hires contractors through a “request for proposal” bidding process. Performance, safety and historical data of the prospective hire are considered when vetting the contractor.

Additionally, every mitigation decision within the hazard tree management program is made by an International Society of Arboriculture Certified Arborist. However, this is not true of its distribution and transmission vegetation management plans. “…Not all tree trimming/removal crews have an arborist, although the contracting companies have arborists on staff…” Milbourn stated.

According to ISA’s website, to take the Certified Arborist exam one must have “three or more years of full-time, eligible, practical work experience in arboriculture” or a “degree in the field of arboriculture, horticulture, landscape architecture, or forestry from a regionally accredited educational institute.” But there’s a catch. No practical or fieldwork portions of the test exist. “The certification does not do a practical test on whether you know how to properly prune a tree. You don’t really have to know species and you can take the test online,” Latta said.

Guzman likened the Certified Arborist exam to the exam used for real estate agents — most people do all of the studying alone with a study guide.

Further, there are different tiers of certifications of which “Certified Arborist” is the most general. This is one of Latta’s qualms with Edison. Their contractors are marking trees without a tree-risk assessment completed by someone with an ISA Tree Risk Assessment Qualification.

“Yes, we understand these arborists are certified, but that doesn’t make them qualified,” she said. “My personal opinion is that all certified arborists should have a background in science.”

Lake Arrowhead resident Joe Pounds had a tree tagged for felling on his property. He had an oak tree that he described as “wrapping around the power line.” Without notice, Pounds said contractors came by his property and marked the tree. He said he came out of his house and began asking questions and making a case for the tree to remain standing. Pounds recalled the contractor saying the tree was in poor health.

Over the next couple of days, Pounds said he called Edison’s general phone line a couple of times, left messages and never received a callback. “I didn’t really think the guy was listening,” he continued. When the contractors returned, they trimmed branches but left the tree standing with its limbs intact. Pounds said the work ended up being minimal. “I understand the whole fire danger concern, but there’s no reason to start cutting down healthy trees,” Pounds said. “You have to stand up and be heard.”

A Second Assessment

Edison representatives said it is possible to request a second assessment. “We can re-evaluate a particular tree if a property owner doesn’t agree [on the initial assessment],” Cusack said.

The first step is to call the inspector listed on the door hanger to gain more information about what concerns the contractor had when making the determination. Milbourn said that if the property owner wants to dispute the claim, a certified arborist will come to the property and review the tree. If there is a concern about the wildlife, Edison will send one of their biologists.

Milbourn said that in the past, Edison biologists have delayed vegetation management projects due to bird nesting season. However, after the birds vacate the nests, Edison carries on with the project.

Kellems found the door hanger method of communication to be problematic. At the San Gorgonio Chapter of the Sierra Club’s meeting on March 9, Kellems presented the pros, cons and concerns of fire vegetation management. Edison representatives declined to attend the meeting.

Kellems called the use of door hangers an ineffective way of communicating with second homeowners who may only occasionally be home. In this case, second homeowners would not even be able to challenge the decision. Property value, especially in the mountain communities, has been tied to the type, age and size of trees. It should be looked at as a monetary asset.

Additionally, Kellems noted that the door hanger makes unoccupied homes a target for theft. The door hangers have the date that it was left. She surmised that these homes would be apt for burglaries.

In attendance was a Crest Estate resident. She told a story about her dealings with Edison. On Friday, Oct. 11, 2019, she arrived home from work and discovered the cedar tree that had been growing on her property for over fifty years had been cut down and left in chunks. “I was shocked and heartbroken,” the resident said. She said that three things had gone wrong — she never received an Edison door hanger and Edison had mailed a notice to the wrong post office box. The third issue began in June of 2019 when, after the cedar was listed for removal, she said she spoke with a forester who eventually delisted the tree. But the tree remained on the list. In November of 2019, the resident filed a claim and received a confirmation, but has not heard from Edison since.

Despite stories like these, Edison insists its actions are necessary for the safety of the mountain communities.

“If we feel the risk is that high and the customer is uncooperative, then we will go ahead and take whatever action we need to do, in the proper manner,” Guzman said. “But we still have a process we’re going to take to empower the customer.”

Property owners with questions about Edison’s hazard tree removal process may contact Edison at hazardtree@sce.com or by calling (833) 774-1393.

Memorial for a Venerated Oak

By Rebecca Latta

A ceremony marked the passing of the sentinel oak at Sunland-Tujunga Library on January 13.

A farewell ceremony at Sunland-Tujunga Library on January 13 marked the end of the life of a beloved friend to many, a majestic Coast Live Oak tree that stood in front of the library for decades. Its passing was celebrated by a gathering of staff, patrons, and friends, who bid it a fond farewell with speeches and poems recited especially for the occasion by two community poets. The poetic tributes to the tree appear at the end of this article.

For nearly five years, the library and the City of Los Angeles had worked to save the tree. But in spite of their efforts, the oak continued to decline. When the tree was near death, it had to be removed for safety reasons. The sad demise of the nearly 60-foot tree was recorded on January 13 by photographer Gary Leonard:

Why should we care so much about one old oak tree? The library’s tree was estimated to be between 100 and 150 years old, representing our local history. Indigenous peoples once used oaks for food, fuel, and shelter. Spanish explorers noted their numbers and named nearby places after them: “Encino” is Spanish for “live oak,” “los robles” means “valley oak.” Oaks provide homes for songbirds, squirrels and owls. Of course, oaks provide comforting shade. And, they are beautiful. There’s nothing like a magnificent oak to connect us with nature. Children and fond memories grow under such old trees, so it’s natural that we come to love them, and grieve when we lose them.

There’s a happy ending to this oak story. As the old oak was cleared away, its branches were chipped to prepare the ground for three young, healthy Coast Live Oaks that took its place.

Three young Coast Live Oaks will reside in the space where the venerable oak once thrived. The trio will grow up with the community and become landmarks in their own right.

Even though the Sunland-Tujunga community treasured their old tree, the three new saplings will grow to be landmarks for those who come after us, bringing the site full circle to delight the next generation.

Oak Care Tips

  • A majestic oak in its native habitat prefers undisturbed soil and a thick carpet of its own dropped leaves surrounding its trunk. An oak surrounded by lawn, flower beds or ivy can die from overwatering, fungal disease, damage from mowers and other hazards. Excavating or paving too near the tree can likewise cause an early death by damaging sensitive roots and exposing them to too much heat.
  • Though winter is the best time to prune deciduous trees (those that drop their leaves) summer is the best time to prune evergreen live oaks Quercus agrifolia (coast live oak) or Quercus wislizeni (interior live oak.) Live oaks drop a few leaves throughout the year and are never bare. They have adapted over eons to California’s hot, dry summer weather by switching to a slower growth cycle when less water is available. So August and September are the best months to trim your live oaks. Beware of over-pruning. If trimmers overdo it, trees can become stressed, causing them to decline and die. Remember, foliage feeds the tree. Removing too much of it puts the tree on a starvation diet.
  • Consult a certified arborist and your city planning department for guidance on tree issues. If you wish to cut limbs from your trees, or grade or build near them, you’ll need a permit. Oaks and certain other tree species are protected by law, so check with your city first. An oak can never regrow a limb lost to a bad cut.
  • Oaks are a natural asset. They’re also a valuable community asset. If you’re lucky enough to own oaks, they are your valuable asset, and you are their steward. Oaks add value to your property, provide privacy, offer shade to lower your air conditioning costs—and save water costs since they’re drought-tolerant. You’ll want to take good care of them.

Old Oak of Sunland/Tujunga Library
On the Occasion of Laying the Tree to Rest, Jan. 13, 2020

By Alice Pero ©2020
Published by permission of the author

Old oak, you have watched us long
While we trampled the underbrush
Nearly 100 years
You watched
While we turned forest floors
Into highways and sidewalks
Finding comfort in books
Inside cool walls of cement
And stone

Once you baffled the sun*
With your thick, fertile branches
Your Old Women** friends
Teaching us the prayers of the Tongva
Though they, too, were almost gone
By the time your seed sprouted

We are grateful for your shade
Your outstretched arms
As children ran about under you
Shouting and playing
Feeling spirit spreading grace

We are grateful for the grace
All live oaks give
More than just precious oxygen
Something of an ancient time
When trees were sacred

Now we must now send you back
To the earth from which you came
With hope that the spirit of trees
Remains in your seed

* In 1910, a Los Angeles Times correspondent wrote about Sunland: In the center of town the oaks are so thick that the sun is baffled
** “Tujunga” in the native Tongva language means “the old woman”

 

Library Tree Celebration, 1/13/2020
Sunland-Tujunga Branch Library

 By Pamela Shea, 9th Poet Laureate of Sunland-Tujunga
Published by permission of the author

Fluttering leaves have bid welcome
To Sunland-Tujunga Library.
Our beloved Coast Live Oak
Has blessed us over a century.

An icon, a landmark,
A beacon, and our friend,
Will live on in memory
Its influence will never end.

Oh dear, beautiful tree,
The time for goodbyes has come.
You’ve adorned our community,
Protecting us from rain and sun.

A sentinel to learning,
You have bridged earth and sky.
Welcoming, inspiring,
Our host and our ally.

Precious one, so majestic,
Standing proudly all these years,
We must now bid you adieu
With our thanks and with our tears.

 

The Twohorned Gall Wasp Might Sound like a Threat, but Don’t Worry, it’s Part of Complex Native Oak Ecology

by Rebecca Latta

If you have evergreen live oaks Quercus agrifolia (coast live oak) or Quercus wislizeni (interior live oak), you might have noticed unusual leaf-drop this winter, along with thousands of small pellets that look like BB shot collecting on your driveway and patio. You might have stepped under your oak tree, and heard those pellets dropping like rain.

leaf galls from oak gall wasp

Leaf galls form on the back of live oak leaves in the second generation of the twohorned gall wasp’s lifecycle.

What you’re experiencing is an unusual population explosion of tiny wasps that specialize in oak trees: twohorned oak gall wasps, Dryocosmus dubiosus. The pellets are tiny leaf galls, formed by the tree in reaction to the wasp’s eggs laid in leaf veins. Magnified, these galls have two small protuberances. So it’s the galls, not the wasps, that earned the name “twohorned.”

An insect with an extraordinary lifecycle, this tiny wasp passes its life mostly unnoticed, high above in the tree canopy. These wasps undergo two generations per year. In the first generation, wasps lay eggs in oak flowers (catkins), causing small galls to form on the blooms and along the edges of new leaves. Larvae feed inside the galls. In the second generation, eggs are laid in midrib and lateral veins on the underside of leaves, causing the tree to form tiny galls. Larval wasps overwinter as pupae in these galls, which often drop from the leaf.

Gall wasp populations vary naturally from year to year, but unusually high populations sometimes occur, causing noticeable yellowing of leaves and premature leaf drop in evergreen oaks. Most infestations are not considered threatening to tree health since twohorned oak gall wasps often kill only parts of a leaf. Unaffected leaves will survive on the same twig, unlike damage caused by fungi that cause oak twig blight and twig girdling beetles, which cause the entire leaf to die.

The good news: Gall wasp numbers are controlled by a host of natural enemies. Fungi, parasites, predators, and competing insects (primarily moth larvae and other wasps) share the gall and kill the wasps and their larvae.

No control for oak gall wasps is known or recommended, however it’s wise to promote good tree health by protecting oaks from stress. Don’t over-prune or over-water. Allow natural leaf litter to remain in place, protecting roots from heat and providing natural fertilizer. Water oaks in times of drought. Although aesthetically undesirable, don’t worry about oak gall wasps: nature will take care of them.

Call your professional arborist if you have questions and for a refresher course on best practices to preserve your oak’s good health.

L.A.’s free tree giveaway for yards and streets hopes to bring 90,000 new plantings

Elysian Park arboretum

You can see examples of some of L.A.’s oldest trees at the arboretum in Elysian Park. As the city embarks on a plan to plant 90,000 new trees in the city, residents can pick species for their yard and for their street.
(Dania Maxwell / Los Angeles Times)

Want a free tree for your yard or neighborhood? L.A.’s Green New Deal to plant 90,000 trees in the city over the next two years is a bonus for residents. The city will give out up to seven free yard and/or street trees to qualifying residents. More than two dozen species are listed on the city’s website, with information about their projected height and defining characteristics. Most are drought-tolerant.

Small trees include crape myrtles with pink, red or white flowers, which can grow to a height of 25 feet. Medium trees range from projected 25- to 35-foot-high silk floss trees with pink flowers and evergreen olive trees to jacarandas, with their mesmerizing blue or lavender flowers, which can grow 50 feet high. Large trees, some of which can grow up to 80 feet tall, include coast live oaks, which are native to parts of L.A.; Canary Island, Italian stone and African fern pines; and deodar cedars, native to the Himalayas.

“A family can sit at their computer in their PJs, pick out a tree online and have it delivered to their yard,” said L.A.’s first forest officer, Rachel Malarich. “All the work is done for them up to the actual planting. But don’t worry. The trees come with stakes, ties and fertilizer pellets, along with easy-to-follow instructions on how to plant them.”

Neighbors can get together and request free trees for their street on the City Plants website. “One of our nonprofit partners will come and assess the location,” Malarich said. “If it meets our criteria — enough space between the sidewalk and the road; no low overhead power lines — they will obtain the necessary city permits and plant the trees for them. The neighbors must sign an agreement to water them for at least the first five years.”

Residents who qualify for yard trees must also sign a commitment to water them. The first five years of a tree’s life are the most important. “If you don’t check once a week, the tree could either die or get stressed out and stop growing,” Malarich said. “If you get it past that point, you can slow down on the watering and enjoy your relationship to a living thing as you watch it grow.”

Malarich advises residents to check their tree once a week. “Before you start your weekend, or when you take out the trash, stick your finger in the soil and see if it’s moist 4 inches down,” she said. “If it’s dry, give it 10 to 15 gallons of water; if it’s moist, wait until next week. You can kill a baby tree by over-watering it.”

“Think of a tree as a baby,” Long Beach City College horticulture professor Jorge Ochoa said. “You need to feed it and invest time in training it to be the best it can be. If your baby grows up healthily, it will give you the pleasure and satisfaction of shade and beauty for many years.”

Info: Go to cityplants.org or call (213) 473-9950.

L.A. plans to plant 90,000 trees in two years. What can we learn from its oldest trees?

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L.A.’s first forest officer Rachel Malarich, right, and Los Angeles city tree surgeon Leon Boroditsky , left, at Chavez Ravine Arboretum in Elysian Park. (Dania Maxwell / Los Angeles Times)

Rachel Malarich faces a pressing task: overseeing the planting of 90,000 trees over the next two years in Los Angeles, home to the largest urban forest in the United States. As the city’s first forest officer, the veteran arborist needs to boost the tree canopy by at least 50% in shade-starved low-income areas by 2028. “The goal is ambitious,” she said. “But through the collaboration of city departments, nonprofits and local communities, we can make it happen.”

Mayor Eric Garcetti, who appointed Malarich to the post in August, said at the kickoff of what’s called L.A.’s Green New Deal, which expands the city’s 2015 Sustainable City Plan: “Trees cool the air, produce oxygen and eat carbon dioxide. Planting trees is the simplest way to combat climate change.” Residents receive a bonus of free trees for their yards and neighborhood streets.

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The Elysian Park arboretum contains about 135 tree species planted more than a century ago.
(Dania Maxwell / Los Angeles Times)

The question at the top of Malarich’s mind right now is which trees to plant in a time of rising temperatures. To find inspiration, she recently took a stroll into the past to visit the city’s first arboretum in Elysian Park, not far from City Hall.

“The arboretum is small, but it has some of the oldest, finest, first or only tree specimens of their kind in Los Angeles,” says L.A. Recreation and Parks tree surgeon supervisor Leon Boroditsky. “We’ve designated many of them as ‘heritage trees.’ ”

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Malarich, a native of San Jose who graduated from Cal State Long Beach in 2005, spent over a decade with TreePeople. As its director of forestry for more than three years, she organized volunteer efforts to plant and care for trees in local communities.

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Pink blooms of a silk floss tree are seen in front of a tall Queensland Kauri pine in Elysian Park’s Chavez Ravine Arboretum.
(Dania Maxwell / Los Angeles Times)

Now she’ll do the same for L.A. on a grander scale. She visited the grove of the city’s older planted trees, which covers a few acres in Elysian Park, best known as the home of Dodger Stadium. More than a century ago, L.A.’s more affluent residents in the Horticultural Society of Southern California needed a place to show off their private collections of exotic trees. In 1893, they petitioned park commissioners and the City Council to secure 10 acres of land in the park and paid to pipe in water.

The Los Angeles Times endorsed the plan at the time. “There is no other park in the country which has such magnificent views, or possesses a climate where the most delicate plants will flourish all winter in the open air,” the newspaper announced on Aug. 22, 1893. Planting in what was called the Elysian Park Arboretum began in December.

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Leon Boroditsky touches the thick outer bark of a tipu tree, which is native to South America.
(Dania Maxwell / Los Angeles Times)

“The founders planted [tree] species from different parts of the world to see what would flourish in L.A.’s. climate,” says Long Beach City College horticulture professor Jorge Ochoa. “Those that thrived were later planted on streets and in parks throughout the city.”

Malarich hopes to garner similar information from the current inventory she is supervising of every tree on L.A.’s streets and in all of its 464 parks. “It will give us data about what species we have and which are doing well. Hard data is necessary for us to succeed.”

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Tree surgeon Leon Boroditsky, left, forest officer Rachel Malarich and Long Beach City College horticulture professor Jorge Ochoa have been tracking tree health and growth in L.A. for years.
(Dania Maxwell / Los Angeles Times)

Malarich, Ochoa and Boroditsky all participated in the city’s tree-planting efforts during Mayor Antonio Villaraigosa’s Million Trees L.A. initiative between 2006 and 2013. The plan fell short of its ambitions, with just about 400,000 trees being planted. It was funded by grants, not taxpayer dollars, and focused on tree-poor areas in South L.A. and the northeast San Fernando Valley.

“Our goal is more realistic,” Malarich says. “Plus we have robust support from city and state funding and nonprofit grants.”

At the old arboretum, Boroditsky points out two graceful old trees, a Cape chestnut from South Africa and a Moreton Bay chestnut from Australia. “These specimens date back to the 19th century, and they’re still doing well,” he said.

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L.A. arborist Leon Boroditsky holds a hand-made map of the oldest trees in Elysian Park’s arboretum.
(Dania Maxwell / Los Angeles Times)

Though spotty, records indicate the arboretum included more than 50 species of trees in the 1920s and that more trees — including a cork oak, a river birch and a small grove of California redwoods — were planted during the following few decades. In 1958, however, Dodger Stadium took a huge bite out of Elysian Park, and the city slashed through the arboretum to build Stadium Way. The six-lane road connected the 5 Freeway and the ballpark, but many arboretum trees were sacrificed.

In 1965 developers introduced plans for a convention center adjoining Dodger Stadium. Nearby residents created a grass-roots organization to fight it. The Citizens Committee to Save Elysian Park not only blocked the convention center but later won battles against a proposed airport, condominiums, oil wells and zip lines. Thanks to the group’s efforts, the arboretum, renamed the Chavez Ravine Arboretum, was declared Los Angeles Historic-Cultural Monument No. 48 in 1967.

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“The arboretum is small, but it has some of the oldest, finest, first or only tree specimens of their kind in Los Angeles,” says L.A. Recreation and Parks tree surgeon Leon Boroditsky. “We’ve designated many of them as ‘heritage trees.’ ”
(Dania Maxwell / Los Angeles Times)

Since then, the committee has continued to stave off development in the park and encourage the planting of more rare and unusual trees in the arboretum, in keeping with its founders’ intentions.

“The arboretum has roughly 135 different species now,” Boroditsky said. “This planting season we’re adding some new ones, including oaks from Arizona, Texas and Mexico that thrive in hotter climates.”

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Los Angeles is in the midst of creating an inventory of all trees on city streets and in parks.
(Dania Maxwell / Los Angeles Times)

“Usually I look at trees in urban areas, where they must be pruned to accommodate overhead wires and they have to fight the sidewalk for space,” Malarich said. “It’s a pleasure to see trees here.” She cranes her neck to glimpse the top of perhaps the tallest tree in the arboretum, a Queensland kauri pine. “It makes you realize how immense and majestic these species can get when they have lots of space.”

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Leon Boroditsky, Jorge Orchoa, and Steve Dunlap, left to right, stand under a tipu tree, which is native to South America’s tropical forests. It’s one of the oldest trees in the city that stands in L.A.’s first arboretum.
(Dania Maxwell / Los Angeles Times)

At one point, she joined Boroditsky and Ochoa under a giant South American tipu tree with a broad, sweeping canopy. “You should see this beauty in the summer when it blossoms,” Ochoa said. “The ground under it looks like it’s covered with a golden blanket.”

Malarich sized up the tree. “It’s way too big for a street tree, but I’d love to see it planted in more parks,” she said. “Standing under a tree like this reminds you that living things this magnificent don’t happen overnight. It requires a long-term investment and commitment to nurture them so they can mature to this age.”

CNPS Native Plant Sale is Saturday, Nov. 2, 2019

Rebecca Latta will Chair this Big Event for Native Plant Lovers

If you’ve never before attended the Fall sale of the California Native Plant Society (CNPS), be sure not to miss this special day!  Stock up on healthy specimens to plant immediately as the weather cools down, right before winter rains. Rebecca Latta will chair the event and be on hand with other expert advisors to talk with those who are just getting started with a water-wise, sustainable native plant garden, as well as those who already understand the value of native plants. Learn how to attract birds, insects and other pollinators and how to make a beautiful yard and garden with drought-tolerant plants.

Rebecca Latta Speaks on Caring for Oaks – September 21 at 10 a.m.

California Native Plant Society’s Riverside-San Bernardino Chapter presents Rebecca Latta on Oak Stewardship

Oaks are the iconic tree of California, providing timeless beauty, shade and a sense of place. Each oak can support thousands of associated species. Now with the stresses of climate change and new pests, oaks need our attention more than ever. Rebecca Latta will discuss how and when to water, when and whether to prune, and all aspects of the care of oaks.