Los Angeles provides residents with free trees to boost urban forest

LA Tree Planting

Urban trees do more than provide fresh air and shade – they turn otherwise bleak and barren neighbourhoods into lush, beautiful, green spaces.

If you live in Los Angeles, greening your street is easy – and free – thanks to a generous new initiative which provides free trees to L.A. city residents for yards, parkways, schools and businesses.

“If you want a street tree in front of your house, all you have to do is sign up and one will appear in a few months; it couldn’t be much easier,” said Elizabeth Skrzat, executive director of City Plants – a public-private partnership funded by the L.A. Department of Water and Power, grants and corporations.

Even if you’re outside L.A., your municipality may offer something similar. For example, Long Beach recently offered free fruit trees to city residents and was pleasantly surprised by the overwhelming response. There are also organisations, like TreePeople, that help provide free trees to help green neighbourhoods.

The Los Angeles tree planting effort is desperately needed, following a U.S. Forest Service survey which predicts that 38% of the 71 million urban trees in Southern California could perish due to invasive pests – a condition exacerbated by extreme heat and drought.

The urban forest in L.A. is one of the largest in the world, comprised of around 700,000 trees. As the city’s premier radiation defense system, it shields people and buildings from solar damage, as well as rising energy costs.

Trees are also an environmental justice issue, according to advocates. A 2008 study by the U.S. Forest Service found that L.A.’s poorest areas have bare canopies –– as low as 5% coverage, while wealthier areas have the highest, up to 37%.

Given the huge health and economic benefits trees provide (they also increase property values), Los Angeles recently called for a “Tree Summit” of experts to propose ways to protect and enhance the city’s urban forests. The free tree planting initiative was part of this plan. Here’s how it works for Los Angeles residents:
Visit cityplants.org and click the “get free trees” link to order a tree. Within a few months, you’ll receive a door hanger with City Plants’ decision to plant or not to plant, based on an inspection of the proposed planting area (not all areas are suitable for trees).

Provided you promise to water the trees for a minimum period of five years, your new urban trees (there may be room for more than one) will be planted within 2-to-6 months after an approved request.

On the day your street trees are planted, you’ll receive another door hanger that includes the species (chosen from City Plants’ list of 60 climate-appropriate varieties), watering instructions and a link to videos advising you on how to care for your trees.

Comparison of Soil Treatments Under Concrete Pavement – Study reveals the fastest way to grow larger, healthier urban trees

At Citygreen, we love science. Since founding, we’ve researched, developed and refined our range of sustainable urban landscape solutions to withstand rigorous testing – and produce outstanding results. So, when our Stratacell structural soil system became the subject of a study comparing the performance of soil treatments under concrete paving, we were keen to see the findings.

The study, entitled ‘Comparison of Soil Treatments Under Concrete Pavement’ was conducted by Thomas Smiley, James Urban and Kelby Fite at the Bartlett Tree Research Laboratory in Charlotte, North Carolina. It examined variations of the two main approaches that have been developed to provide rooting space for trees in urban areas – supported pavement and structural growing media.

Overall, the study found that structural load bearing modules (like Citygreen Stratacell and Stratavault systems) grow the largest, healthiest trees in the fastest time. It also highlighted the superior all-round performance of these systems compared to others.

Study goals

The purpose of the study was to compare the growth of trees in different supported pavements and structural growing media. The aim was to determine which methodology would produce the largest, healthiest trees in the shortest time.

A key driver behind the research was canopy cover. Tree canopy provides a huge range of environmental, economic and health benefits, including:

  • Combats climate change by reducing greenhouse gas emissions
  • Provides natural shade and cooling
  • Conserves energy and reduces power costs
  • Enables water filtration and retention
  • Provides habitats for wildlife
  • Increases property and area values
  • Promotes health and wellbeing
  • Contributes to a sense of place
  • Encourages community interactions

The faster tree canopies grow, the sooner the benefits can be enjoyed by cities, stakeholders and communities. Accordingly, the study sought to determine which system would produce the highest volume of canopy cover in the fastest time.

SUP Trial Plot Sept 2017


To achieve the study goals, two plots were established at the Bartlett Tree Research Laboratory. The first plot was installed in 2004, exclusively for Study 1, which examined five variations of supported pavement systems. The second plot was established in 2014, specifically for Study 2, which examined six variations of structural media.

Citygreen’s Stratacell system was part of Study 2, which also included an open control, compacted control, sand based structural soil (SBSS), gravel based structural soil (GBSS) and another structural load bearing module, similar to Stratacell.

At the start of Study 2, on 19 August 2014, containerised 18mm caliper Liriodendron chinense trees were installed in the centre of each plot. A 5cm thick layer of concrete was poured over the plot, with a 20cm hole centred on each tree. A soil moisture sensor was also fitted.

Over the following three years, the trees were measured and assessed regularly against key performance indicators. On 23 October 2017, the trees were severed at the root for final measurements and findings. During the excavation, soil was removed from the roots, leaving the mass intact for examination.

Airspade removing soil from roots

Pressure Wash and Hydrovac of roots

Weighing of each root system

Key findings

Overall, the study found that soil treatments that provided a low density growing media (such as Citygreen Stratacell and Stratavault) resulted in the largest, healthiest trees in the shortest time. These findings were consistent across Study 1 and Study 2. However, in Study 2, the tree growth differences between the systems were more pronounced than in Study 1.

The structural load bearing systems, including Stratacell, performed extremely well in Study 2. Compared to the compacted soil, SBSS and GBSS, these systems consistently achieved the highest scores across multiple measures of tree health and growth, including:

  • Tree trunk diameter
  • Tree height
  • Foliar Colour
  • Number of roots > 1.2cm diameter
  • Maximum root spread
  • Maximum root depth
  • Weight of tree parts
  • Moisture content of soil

Stratacell outperformed all other systems in terms of maximum root depth, moisture content and foliar colour. Like the other structural load bearing module, it also produced significantly larger trees with more large roots than other treatments, including compacted soil, SBSS and GBSS.

The final findings were consistent with observations throughout the study, which reported that the trees in structural load bearing modules began to diverge from other treatments by the end of 2015. Similarly, in 2016 and 2017, there were significantly larger than most other treatments.

Trees planted in structural load bearing modules

Tree roots developed in Stratcell and Silvacell vault systems

Root system grown in gravel based Structural Soil


The study concluded that structural load bearing modules (such as Citygreen Stratacell and Stratavault) are superior for growing large, healthy trees in the fastest times when compared to other systems, such as compacted soil, SBSS and GBSS.

While the study did not point to a ‘best product’, it proved the methods that support the load on a pavement and keep that load off the growing media work better than those that don’t.

This is good news for urban planners, landscape gardeners, architects and developers. It means that, simply by choosing a structural load bearing soil system, they can achieve the canopy cover they require years sooner than they might with other systems.

Similarly, cities, communities and individuals can enjoy the environmental, economic and health benefits of tree canopies faster and for longer.

Download the full report

Click here to download the full ‘Comparisons of Soil Treatments Under Concrete Pavement’ study.

A green view: How seeing trees from your window improves wellbeing

Green View

A new study from the UK highlights the importance of urban trees as a matter of health. The study, which combines research from England and New Zealand, concludes that people who can see trees from their window are happier and healthier – particularly in high density housing areas.

Now, New Zealand campaigners are citing the study to strengthen their argument for improved tree protection measures.

New Zealand’s Tree Council secretary, Dr Mels Barton says: “The link between people living at one property and valuing something else across the road comes out as so, so, important – and it’s not been demonstrated before,” she says. “We will definitely be waving [the report] around; there is not enough research into the benefits of urban trees.”

The study refers to the increase in physical and mental health conditions that result from urbanisation. It also presents evidence of how urban trees help combat these conditions by providing “indirect nature experiences”.

“With the rise in urban living, most people now spend much of their day indoors, therefore the green viewscape from home or from work often constitutes by far their most common nature experience. Having a room with a view of nature does not necessarily mean that people are continuously experiencing that view. Instead, people spend a significant amount of time with their attention directed towards specific tasks, and the presence of a window with a natural scene allows micro-restorative experiences, with scenes that are more fascinating being likely to be more restorative. There is robust evidence to suggest that indirect nature experiences provide a broad range of health and wellbeing benefits, including increased psychological wellbeing, improved cognitive function and concentration, reduced healing times and reduced stress at work,” it says.

Given the health benefits of urban trees, Dr Barton says the study supports the idea that trees belong to communities, not to individuals.

“Your tree is not just your tree,” she says. “It really belongs to those people who can see it. It really affects people’s well-being and it’s important to them. So, it shouldn’t be your right to make the decision to remove it. Trees are being removed every day. We want that to stop before it’s too late.”

The study also has implications for inner city streetscapes, as well as residential areas.

“The layout of cities and where we put specimen trees is really important”, says Dr Barton. “Auckland in particular has developed ad-hoc with all these pocket parks as development contributions that are too small to put a house on … they’re really of almost no benefit.”

The bottom line, according to Dr Barton, is that trees should be planted where they can be seen – and where their benefits can be enjoyed by many.


A master plan to manage Tallahassee’s urban forest


Tallahassee boasts one the highest tree canopy coverages in the U.S. At 55% coverage, Tallahassee’s tree canopy is iconic – and now it will be managed properly under a new Urban Forest Master Plan (UFMP).

The UFMP was commissioned in March 2017, six months after Hurricane Hermine highlighted some challenges related to Tallahassee’s tree canopy. During the plan’s development, Hurricane Michael caused further damage to the city, reinforcing the need for a management plan for in the interests of public safety.

Approved in December 2018, the UFMP is a long-term plan of action for proactive and effective urban forest management. As well as ensuring that Tallahassee’s urban forest improves in quality over time, the plan will support the City’s needs relating to storm hardening, infrastructure and growth.

Large, vibrant trees make Tallahassee a unique community to live in and visit. When managed properly, the trees will enhance the sense of plan, plus add economic and social value to the city. Importantly, they will also have a positive impact on infrastructure and safety, rather than causing unnecessary costs.

With limited information existing on the state of Tallahassee’s urban forest, the development of the plan required extensive and detailed research. It included an analysis of urban forest distribution and composition, a review of tree management policies and procedures, plus vital public feedback.

While measurable change will take time, the 20-year plan provides recommendations that can implemented gradually to achieve three overarching goals:


Goal 1: Improve Canopy Quality

While the species diversity of Tallahassee’s urban forest is good, there’s a high proportion of weak, wooded trees – around 38% in total. These trees simply don’t live long. Plus, once they achieve mature size, they decline due to structural issues and decay. The UFMP aims to improve the quality and longevity of the urban forest by completing a public tree inventory and emphasising the correct mix, planting and placement of trees.


Goal 2: Maintain Canopy Levels

Even with high populations of less desirable species, Tallahassee’s dense tree canopy is still a major asset. The City will continue to prioritize maintaining a high level of canopy, while also focusing on “re-composition”.


Goal 3: Engage the Community

With 70% of Tallahassee’s tree canopy located on private property, the City is counting on citizens, community groups and stakeholders to work together to achieve common goals.


For more information on Tallahassee’s UFMP, visit: www.talgov.com/tallytrees

UK Environmental Secretary unveils new protection for urban trees


New plans announced by UK Environment Secretary Michael Gove will provide urban trees with increased protection against felling.

The proposals, which were recently released for consultation, required local councils to consult with communities before cutting down trees in England’s cities and town streets.

The move follows a prolonged protest against the destruction of thousands of urban trees in Sheffield, in the English county of South Yorkshire.

As part of a plan to resurface the city, over 5,500 street trees – including 2,000 deemed to be healthy – were chopped down and replaced in Sheffield. This sparked a three-year protest, which deployed van loads of police in Sheffield’s leafy suburbs, before a compromise deal was reached late in 2018.

“It’s right that the views of local people are at the heart of any decision that affects their community – and the futures of the trees that line their streets are no different”, said Mr Gove.

“Trees have often been rooted in our towns and cities for many years and are undoubtedly part of our local heritage.”

“These measures will enhance the protection given to urban trees, ensuring residents are properly consulted before trees are felled and safeguarding our urban environment for future generations.”


The proposals include the following measures:

  • New requirements for councils to consult residents on plans to chop down trees;
  • Responsibilities for councils to report on felling and replanting;
  • More powers for the Forestry Commission to tackle illegal felling.
  • Strengthened protection for wooded landscapes.


In addition to the proposed new protections, the Government has committed to planting one million trees in urban areas, on top of 11 million trees nationwide by 2022. To drive this pursuit, Mr Gove appointed Sir William Worsley to be the national tree champion in 2018.

In support of the new proposed measures, Sir William said: “Urban trees are an amazingly valuable natural resource, and with this consultation I hope we can take further steps towards strong and robust protections to ensure their futures.”

“By planting the right trees in the right place, we can ensure that they continue to improve health and well-being and encourage people to enjoy the outdoors.”

Richard Greenhous, director of forest services at the Forestry Commission, also spoke in support of the new consultation.

“The Forestry Commission recognises that our trees and woodlands are under increasing pressure, especially in and around urban areas”, he said.

“With this consultation, we hope to be able to better protect more of our cherished woodlands from illegal felling.”

World Forum on Urban Forests raises global Call to Action

Urban Forests


Held in December 2018 in Mantova, Italy, the inaugural World Forum on Urban Forests has moved forward by launching an eight-point Call to Action. The Call to Action aims to maximise the benefits of global urban greenery, create healthier and happier cities, and mitigate the impacts of climate change on the world’s cities.

The Call for Action promotes a vision where urban and peri-urban forests, trees and other green infrastructure will be acknowledged as critical infrastructure and used as a tool for achieving sustainable development goals.

The Forum put forward the following set of eight forest solutions to make cities greener, cooler, healthier and safer.

  1. Expanding canopy cover in cities and “using the right tree in the right place”;
  2. Promoting community gardens, urban agriculture and urban flood forests;
  3. Increasing the number of green buildings and vertical forests and encouraging installation of green roofs
  4. Converting neglected areas, courtyards and brownfields into green spaces;
  5. Developing political agendas that promote green spaces and urban forests;
  6. Using existing technical guidelines to plan, design and manage urban forests and trees;
  7. Creating and promoting green jobs and economic opportunities; and
  8. Monitoring the ‘heat island effect’ in cities to support strategic planning or urban forests.

The World Forum on Urban Forests was attended by government representatives, urban planners, arborists, landscape designers, architects, academics and other forestry experts. It discussed global greening strategies, long-term collaboration opportunities, and identified sustainable solutions for a greener future.

Over 600 participants from around the world, including over 150 speakers, shared positive examples of urban forest design, planning and management, illustrating the role of forests and green spaces in creating more resilient and sustainable cities.

For more information on the World Forum for Urban Forests, visit www.wfuf2018.com.

The positive impact of trees – from economics to health

Positive impact of trees

Considering Australia’s excess carbon emissions, trees are useful to have around. Through the miracle of photosynthesis, trees breathe in carbon dioxide and breathe out vital oxygen. However, trees do far more for Australia than help with our greenhouse problem.

For a start, trees make us happy. Studies from Australian universities analysed 2.2 million tweets on Twitter and found that tweets made from parks were more positive in nature than tweets from built-up areas. So why are people in parks so happy?

In a world that’s becoming increasingly urbanised, parks provide a welcome respite from the stress of living in cities. With nine out of 10 Australians living in urban areas – and two thirds of us living in capital cities – more people are flocking to parks to exercise, meet friends and attend events. We’re also getting back to nature to combat the health risks – both physical and mental – of high-density urban living.

Decades of research shows that experiences of nature are associated with a wide range of positive health outcomes, including improved physical health (such as reduced blood pressure and allergies), improved mental health (such as reduced stress), greater social wellbeing and uptake of positive health behaviours. Whether it’s walking the dog, strolling in the park or playing games outdoors, being connected with nature provides proven relief from stress and anxiety.

Then, of course, there are the environmental and economic benefits that urban trees undoubtedly bring. According to environmental planners at Griffith University, Australian cities are getting hotter, noisier and more crowded – and climate change is causing more heatwaves. Rather than increasing air-conditioning, which in turn increases carbon emissions, the better solution is green infrastructure – street trees, green roofs and walls, and vegetated surfaces.

Compared to hard surfaces like concrete, asphalt and stone, which increase urban temperature, green roofs and walls can naturally cool buildings, significantly lowering the need for air conditioning. Plus, according Griffith’s environmental planners, shading from strategically placed street trees can lower surrounding temperatures by up to 6 degrees – or up to 20 degrees over roads.

Considering the wide-reaching positive outcomes to environment, happiness and health, if there’s one thing Australia’s economy needs more of, it’s trees.

Milan’s plan to plant three million new trees by 2030

3 Mil trees

Milan in Italy is often plagued by muggy, almost tropical weather. However, an ambitious plan to plant three million new trees by 2030 could offer relief from the stifling weather. As well as helping to lower temperatures, the trees will play a major role in mitigating pollution and combating global warming.

Officials estimate that boosting the number of trees by 30% in the broader metropolitan area will absorb an additional five million tons of carbon dioxide each year (four-fifths of the total produced by Milan), plus reduce harmful PM10 small particulates by 3,000 tons over a decade. They also predict the new trees will reduce city temperatures by a significant 2C.

Renowned architect Stefano Boeri said the current green canopy of the Lombard region’s capital accounts for only 7% of the urban area – well below other European cities, like Frankfurt at 21.5% or Amsterdam at nearly 21%.

The plan is to increase this green canopy to between 17% and 20% by 2030 and, ultimately, lower

temperatures in a city where the evening mercury can be 6C (10.8F) higher than in the surrounding area.

According to city statistics, Milan endures around 35 tropical nights a year. Because of its location close to the Alps, there is very little wind to clear pollutants that become blocked in by temperature inversions, where a layer of cool air is covered by a layer of warmer air.

Plus, as Damiano Di Simine, the scientific coordinator in Lombardy for the environmental group Legambiente, describes, this also contributes to urban heating.

“It means the discomfort from thermic inversions is terrible, because the climate is very stationary. Planting trees will help this”, Mr Di Simine said.

Some ad-hoc projects have already contributed to environmental improvements, such as Mr Boeri’s Vertical Forest residential towers, completed in 2014. However, if Milan’s plan is any indication, the Vertical Forest is just the beginning.

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