Nature in the City - Austin Blog

^{Written by Keith Babberney | Forester | Community Tree Preservation Division | City of Austin} 

In Austin, we love our trees, but we don’t always know the best way to show them our love. People often assume they should fertilize to improve tree health, but plants that are well adapted to Central Texas soils generally don’t need extra nutrients. This article will help you decide if you need to fertilize and what the best methods are to do it. 

What is fertilization?

Fertilization simply means adding material to soil (or sometimes directly to plants) that provides the elements plants need. Trees, like all plants, require certain specific nutrients to survive. Most of these nutrients are drawn from the soil by roots and their associated fungal network. If one or more nutrients is lacking, the tree may be unable to complete the process of photosynthesis, which is how plants make their energy. 

Though hydroponic gardening proves plants can survive strictly on chemical nutrients, healthy soil is a thriving community of bacteria, fungi, insects, worms, and other living things. Plant stress may be caused by problems in the ecosystem that can’t be helped with fertilizer.  For example, in compacted soil, roots struggle to get air and water, so nutrient levels are a secondary concern. In alkaline soils like we have in Austin, certain nutrients may be present but unavailable to plants. Fertilizer should never be added to soil without confirmation that some nutrient is needed. It is important to follow label instructions carefully when applying any product.

Plant health requires more than just nutrients from fertilizer. A healthy soil ecosystem supports healthy trees.

Should you fertilize?

When nutrient deficiencies exist, fertilization can restore the tree’s ability to meet its needs and maintain health and vigor. On the other hand, when required nutrients are already present in soil, adding additional material can cause more problems than it solves. 

The first step should be to have the soil tested for current nutrient levels. Nurseries sell home kits that can be helpful, but the most reliable option is to send samples to a laboratory for testing. Texas A&M University offers affordable testing that includes full recommendations based on current soil conditions and the plants of concern. Some commercial labs also perform testing services for the public. Basic testing generally measures levels of the three major nutrients (nitrogen, potassium and phosphorus) and most micronutrients (such as iron, calcium, and boron), as well as providing pH analysis. Specialized tests are also available if a particular problem is suspected.

Sending a soil sample to be tested is important to determine what nutrients are needed, if any.

What kind of Fertilizer?

Not all fertilizers are the same. They can be powders, liquids, or granules. The ratio of nutrients and inert ingredients varies from product to product. Packaging should always include three numbers that tell how much of each major nutrient is present. If the bag says “N-P-K 20-10-15,” we know the fertilizer is 20 percent nitrogen, 10 percent phosphorus, and 15 percent potassium.

If your soil test shows only one nutrient is deficient, you would not want a 20-20-20 product. For example, if you only want to supplement nitrogen, you would look for a package marked with a high first number and low second and third numbers, something like 5-0-0 or 6-1-1. The recommendations from the soil lab would tell you how much of each nutrient to apply per square foot, and a quick calculation would determine how much of the package to use.

Determine the amount of each major nutrient in a bag of fertilizer using the three numbers on the package representing percentage of N-P-K. This 50 lb. bag is 16% nitrogen, so it contains 8 pounds of nitrogen.

Where should you fertilize?

Once you decide which fertilizer to use, you need to know where to put it. Tree roots spread outward from the trunk, extending well beyond the ends of the branches. The deepest roots anchor the tree, while the fine roots that absorb water, air, and nutrients are normally close to the surface. The more soil volume we affect in the root zone, the easier it will be for the tree to take advantage of the improvements.

It may be necessary to treat your whole yard to reach all your tree's roots.

On urban and suburban lots with mature trees, this usually means we want to treat the entire yard. Turf grass often becomes significant to the job. Grass forms a dense mat of roots that compete well for soil resources, particularly water. While grass roots normally only grow down a few inches, trees can have feeder roots up to two feet deep.

Of course, not all soils are even one foot deep, and some soils are so compacted that roots can’t grow very deep. The basic principle is that the roots we want to reach are close to the surface, spreading as far as 3 times the height of the tree. Any product we add to the soil will be more available to the tree when and where water is present. With this in mind, there are four basic ways to provide what’s needed to the trees. Each has advantages and disadvantages.

How should you fertilize? Four Options

1. Surface Application 

The simplest method—and often the cheapest—is to broadcast materials over the surface of soil and let gravity and water carry it to roots. Plants have evolved to get their nutrients this way, and it still works fine. A wide range of products can be broadcast; they are sold as powders, granules, or pellets. They can be spread by hand with scoops or shovels, or a wide range of machines are available that can help distribute materials evenly over a large area.

Timing of surface applications can be important. Adding a concentrated chemical to plants during hot, dry weather can cause “burning” damage to plants, so it’s better to apply granular fertilizers during mild weather. Often, spring and/or fall are preferred. No matter when it is applied, fertilizer should be watered in after spreading to wash the chemicals from the plants and carry them into the soil. Trees prefer a slow, deep soaking to a short, light sprinkle.

This is not as big an issue when organic materials of lower concentration are used (such as N-P-K 1-0-0 instead of 20-0-0). A quality compost can be spread up to ½” thick any time with little risk of damage to plants. Not only does compost provide mild levels of nitrogen, but as it decays it feeds and invigorates the soil ecosystem. Healthy soil supports healthy plants.

However, surface application is not always the best choice. Some disadvantages include:

• On steeply sloping lots or severely compacted soils, fertilizers may wash away before they can be absorbed into the soil, which not only wastes money but can cause problems for wildlife along our creeks and lakes.
• It often requires a lot of work to move heavy bags around and spread the material.
• A big pile of compost might take up valuable space that has to be reclaimed quickly.
• Damage to plants can occur if products are not spread evenly. Concentrated pockets of chemical that can be toxic to roots and leaves.
• After spreading, fertilizer should be watered in, which adds a step to the process and might take too much time.
• There may be a delay between application of the product and visible results—which suits trees fine, but doesn’t always sit well with homeowners.

A wide range of devices are available to help spread fertilizer evenly over the surface of a lawn or garden.

     2. Subsurface Application

Another method of fertilizing is to apply materials directly into the soil, below the surface. This could mean digging a grid of small holes and filling them with dry fertilizer. Some companies offer fertilizer “spikes” that can be pushed into the soil, where they slowly dissolve and become available to plants. The problem with these techniques is that the material does not readily move through the soil. It leads to isolated pockets of toxic soil, surrounded by larger pockets of soil where plants can access the nutrients. The majority of the soil remains unaffected.

The most effective subsurface technique is often marketed as “Deep-root” fertilization or feeding. Fertilizer is dissolved in a large tank of water. A large, metal spike is pushed into the soil and the liquid is pumped by a machine below the surface. This requires specialized equipment, so generally professional arborists or landscape companies are the ones to do it. Some consumer equipment can work in a similar way, but tends to be much smaller and slower to treat a large area.

There are several advantages of deep-root applications:

• The liquid is injected below grass roots, so trees can benefit without having to settle for what the grass leaves behind.
• Because it goes directly into soil, there should be little or no runoff with this method.
• The solution used can be customized to include soil conditioners, like humates or mycorrhizae.
• Nutrients are potentially available to the plant immediately.
• Chemicals and are not as likely to burn plant tissues because they are diluted and spread out through the soil more effectively.
• The injection needle can puncture layers of compacted soil, allowing water, air, and nutrients to penetrate more deeply than they would with surface application.

This method can be problematic, though.

• In severely compacted, shallow, or rocky soil, it may be impractical to insert the injection wand deep enough to penetrate the grass.
• In softer soils, the needle may go too deep and place the chemicals below the tree roots, where it is wasted.
• The liquid sometimes splashes out of the injection sites, which can be messy, and some chemicals may stain concrete or other hardscape.
• Pressure from the pump sometimes pushes up large plates of soil, which can shear off delicate feeder roots between the plates.
• And, because the equipment is somewhat large and expensive, it can create logistical headaches and might not be affordable to smaller companies or individuals.

Arborist Salvdore Martinez uses a deep-root injection system to pump liquid nutrients and soil conditioners below the soil surface. Photo courtesy Arborilogical Services.

     3. Direct Injection

Another possibility is to inject liquid nutrients directly into plant tissues. Small holes are drilled through the bark of the tree trunk or primary roots into sapwood, then specialized equipment is used to push the chemical into the tree’s vascular system. Several techniques and devices are available for these injections.

As an ongoing maintenance plan, injections are not a good choice.

• The drilled holes can provide entry for decay or disease organisms.
• Injected chemicals don’t always move through the tree as well as what comes in through roots naturally.
• The chemical is often quite concentrated, which can damage the tree’s cells at injection sites.
• Even at their best, injections only have a short-term effect on the plant and no effect on the soil.
• Without some kind of soil remediation, the process would have to be repeated at some interval, perhaps annually, requiring new drilling each time.

Still, injections have their place. The effect is almost immediate, so if there’s a question about which nutrient is deficient, injections can be used to diagnose the problem. If the soil is severely compacted, steeply sloped, or very limited in volume, injections or spraying may be the only practical ways to get adequate amounts of the chemicals into the plant.

On difficult sites, fertilizer can be directly injected into tree trunks opr surace roots.

     4. Foliar Application

A final technique involves dissolving nutrients in water and spraying the solution onto the leaves of plants. The nutrients are absorbed through the leaves to become available for photosynthesis and other processes. Like injections, spraying is not usually a good choice for ongoing treatments.

• Timing is critical to ensure the leaf pores are open and active to absorb the chemicals.
• The effect is short-lived and does little to improve the soil in the root zone.
• As with any spraying, wind might blow the chemicals onto other plants or property where it isn’t needed and might cause staining or other problems.
• Technicians may struggle to get adequate coverage on the highest leaf surfaces to have a significant effect.

Like injections, foliar treatments can be useful in certain situations. The effects of spraying will be evident quite rapidly, so it can help diagnose a deficiency when other methods are inconclusive, and on difficult sites injection or spraying may be the only two practical methods to affect a particular tree.

A qualified arborist can help you determine if your trees need treatment and if so, which methods are best suited to your landscape. To find one, and to learn more about proper tree care practices, visit our Tree Information Center.

Article written by Keith Babberney, Forester with the City of Austin's Community Tree Preservation Division.

This information is sponsored by the City of Austin. Learn more about trees and resources at the Tree Information Center! 

www.austintexas.gov/trees 

Hi, I’m Anish. I will be a senior at McNeil High School in the fall of 2023. After being a member of the 2022-2023 Youth Forest Council, I decided to continue as a fellow for the 2023-2024 Youth Forest Council. With the help of my mom, I developed a passion for gardening during quarantine for Covid. My position as a member of the Youth Forest Council and my interest in horticulture helped me choose my Community Action Project (CAP). For my CAP, I decided to plant native trees in parking lot medians and create a courtyard oasis for students with special needs. 

Volunteers at McNeil High School prepare to plant a Texas Mountain Laurel tree.

Planting Trees

Thanks to TreeFolks, a local non-profit organization spreading awareness about our urban forest, we received twenty-seven Texas native trees. These included the following species: Mountain Laurel, Anacacho Orchid, Oak, Pecan, Eve’s Necklace, and Desert Willow. With the help of the McNeil Green Club, an afterschool program aimed to promote environmental sustainability, nine Mountain Laurel trees were planted in McNeil High School’s courtyard for students with special needs. The remaining eighteen trees were planted across three of McNeil High School’s parking lot medians as a part of a McNeil High School NHS volunteering event. Planting trees around impervious surfaces, like parking lots, reduces the harmful Urban Heat Island Effect which occurs when impermeable infrastructure retains the sun’s heat. 

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Two National Honor Society volunteers plant a tree near the school parking lot, mitigating the heat island effect.

Courtyard Oasis

At McNeil High School, there is a specialized area for students with special needs referred to as the J-wing. Inside the J-wing lies a large courtyard with seven concrete garden beds and a raised bed along the wall. At the start of the year, the courtyard was overrun with monstrous weeds. Since special needs students have less accessibility, it can be difficult to create a welcoming environment. Over the course of the year, the weeds have been removed and replaced with over 40 native plants like Autumn Sage, Yucca, Muhly Grass, Gaura, Coneflower, and more, from Hill Country Water Gardens and Nursery, a local garden center. Going into the Courtyard Oasis project, I knew extra funds would be needed. For that reason, I applied for the Office of Sustainability’s Bright Green Future School grant. I received $3000 to cover the cost of tools, materials, and plants. While it was a daunting task, with the help of my school staff and volunteers, we were able to convert McNeil High School’s J-wing courtyard into an oasis. 

These eight hard-working volunteers just spent a day planting, weeding, and mulching the new courtyarrd gardens.

Lessons Learned

While the project has been a success, it hasn’t gone without its fair share of setbacks. The challenges along the way helped me grow into a better gardener and planner. If I could share my knowledge with others about beautification projects, I would recommend clearly communicating far ahead of time. For example, reaching out to volunteer organizations weeks in advance can ensure that you get the desired number of volunteers. Although weeds and irrigation can be difficult to manage at times, spending time in nature can be a rewarding experience. I have loved working with 37 unique volunteers for a total of 14 hours in the creation of this project. Watching trees like Eve’s Necklace thrive and perennials like Autumn Sage blossom over the last few weeks has been magical! As we head into the future, the plants and trees will create a nurturing green space for incoming students. Growing green not only helps the environment but the community as well. 

Anish and another McNeil student planting an oak tree in a parking lot median.

This article was submitted by Anish Palley, a past Youth Forest Council intern and current fellow. 

This site is sponsored by the City of Austin. Learn more about trees and resources at the Tree Information Center! 

www.austintexas.gov/trees  

Take a journey with Kylie via her StoryMap.

Nature has always been with me and has been a grounding resource for me. I can rely on it to make me feel better. I look for it everywhere, and that’s why this project has been important to me. I think everyone should have something in their life that they can rely on. Nature is an easy one. Even in concrete jungles, you will find a sprout of grass coming out of the sidewalk cracks. ~Kylie

Kylie is a recent graduate of the City’s Youth Forest Council (YFC). Each YFC member completes a Community Action Project as part of their year-long internship. For her CAP, Kylie wanted to document urban nature throughout her travels as a college student abroad. Taking root in Austin, TX, Kylie's love of nature and appreciation for trees has blossomed in various beloved parks and greenspaces as she traveled across the nation and to Spain and France. 

Kylie used ArcGIS to map her journey and an ArcGIS StoryMap to walk us through her first-hand accounts of the nature she encounters during her travels. Through the Nature is Always with Us StoryMap she invites us all to follow along.

​Kylie is currently studying environmental policy at Syracuse University in New York. She aspires to be a shaping force of climate activism in the future. We're proud to be her starting point on what we know will be a long, sustainable journey. 

Blog post by Amelia DeVivo, Youth Forest Council Program Coordinator, Community Tree Preservation Division

This site is sponsored by the City of Austin. Learn more about trees and resources at the Tree Information Center! 

www.austintexas.gov/trees  

In 2020, the City of Austin's Community Tree Preservation Division released the Community Tree Priority Map. This resource prioritization tool is for everyone to use including city programs, partners, policymakers, Urban Forest Grant applicants, arborists, and more. It provides access to relevant data comparable across Austin’s neighborhoods. For example, tree canopy data helps uncover disparities in historically under-canopied areas. This enables people to decide where activities like planting, tree care, and community outreach could occur around Austin. 

Developing the tool entailed consulting with many people, including arborists, planners, tree planters, students, and others. The City's Youth Forest Council and Park Ranger Cadets engaged with and endorsed the recommended data to be used in the Priority Map. During that process, they expressed their admiration for trees through words of gratitude. One youth participant wrote, 

“I am thankful for the shade trees bring on hot summer days. I am thankful for the way they calm me down so I am able to listen to nature and feel at ease. I am thankful for the clean air they give me so I am able to breathe.”  

The map matches survey priorities with data points including tree canopy, temperature, mental health, and air pollution. It then bakes this info into a simple score. In the map, the orange zone equals a higher score and higher scores mean higher priority. These neighborhoods are where we recommend investing most heavily in new trees and community stewardship projects. 

In the end, priority areas help us gauge success. For instance, are activities like tree planting occurring in higher priority areas? So far the data tell us, that 60% of tree planting occurred in the moderate to highest need areas over the last five years. Moving forward, we will encourage and prioritize tree planting, tree care, education, and inspiration projects in these areas.  

Austin’s Community Tree Priority Map 

Interested in learning more? View the interactive map here!

Ready to play? Download the data for your analysis here.

About the Map

The Community Tree Priority Map is organized into 2 categories, High and Low Priority. Nine data inputs are standardized and summed across the categories of Environment, Social Vulnerability, Community Investment, and Health & Well-Being. Each category was normalized to minimize its impact on the priority score.   

Article contributed by Alan Halter, GIS Analyst Senior with the Community Tree Preservation Division. Email your questions to Alan by clicking here.  

Additional Information  

Stewardship Investment: The Community Tree Report seeks to share how the City invests in the activities that support Austin’s urban forest and community of stewards. The Report features investment visualizations, an interactive map of projects, and the raw data for your analysis project.  

Urban Forest Benefits: Urban Forest Inventory and Analysis Program (UFIA) completed an assessment in Austin in 2016. Austin’s urban forest monitoring program produces estimates of the quantity, health, composition, and benefits of urban trees and forests. 

City of Austin Strategic Direction 2023 (SD23) Alignment: The Community Tree Priority Map supports the SD23 Government that works for all (GTW.10).  

Do you have an idea to benefit Austin's urban forest in a high-priority area? We encourage you to explore and apply for the Urban Forest Grant, which can help fund your tree planting, care, education, and inspiration projects. 

This information is sponsored by the City of Austin. Learn more about trees and resources at the Tree Information Center! 

www.austintexas.gov/trees 

Today’s sustainability spotlight is shining on Youth Forest Council Intern Cain Ly. For her Community Action Project, Cain engaged with teachers and students at Garza High School this past spring. She organized over 100 volunteers to participate in a series of tree plantings and the creation of a food forest on campus. 

YFC Intern Cain Ly directs volunteers at Garza High School's tree planting.

“What she’s done has really galvanized the teachers and so many students on campus to get involved with these sustainability projects,” said Scott Cook, a Social Science teacher at Garza. 

Garza High School is unique in its status as an alternative school where students adopt a self-paced curriculum. Located in East Austin, their philosophy is that a 'student’s personal adversities and life difficulties can be harnessed as strengths for their personal betterment.’ One of the features of the school is a daycare center, where children are cared for while their parents are in class. This helps ensure young parents can stay in school and graduate.

Garza High School's child care center provided some volunteers for the food forest planting.

Noting the opportunity to provide a hands-on experience centered on urban forest health, Cain invited the youngsters to assist their parents and other student volunteers in a tree-planting event. Below are photos of Cain leading young parents from her high school as they teach their children how to plant a tree and inspire the next generation of nature lovers from right here in Austin, Texas. 

Volunteers planting a fruit tree at Garza High School

Cain Ly's food forest project engages young children, older kids, and adults.

We're proud of the work Cain accomplished with her volunteer crew at Garza High School. We hope the community will continue to enjoy their new food forest for years to come.

Article by Cain Ly, Youth Forest Council intern, City of Austin, Texas

Visit the Tree Information Center at www.austintexas.gov/trees.   

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Help make Austin a greener, cooler place to live where everyone has daily access to nature.

Join us on social @NatureCityATX, where we're cultivating connections!  

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Did you know Austin residents can get funding for projects that care for trees in their neighborhoods? They can, through the City’s Urban Forest Grant!  

Applications are due January 1st and July 1st! 

Non-profits, neighborhood groups, schools, and other organizations are eligible to apply for a grant to fund tree projects on public property like: 

• Planting trees at schools and other community spaces,

• Tree care and maintenance, such as pruning and mulching,   

• Disease control and invasive species management, and    

• Tree-centered, community engagement, art, and education projects!  

Urban Challenges

Urban trees face different challenges than their countryside counterparts. If we want to live in a city of trees, we must provide care for those we have and plant new ones. When you apply for a grant, you’re investing time and energy into your community that will benefit future generations.  

Funding is allocated based on a range of criteria. Priority will be given to projects that: 

• Increase tree canopy cover and maintain existing canopy

• Prepare for changes to our climate 

• Educate the public about trees and tree concerns 

• Are located where the need is greatest, based on our Community Tree Priority map 

The Community Tree Priority Map identifies areas of Austin that are most in need of new tree canopy.

Click here to Explore the Community Tree Priority Map!

Create Your Own Grant Project

We know Austin is full of passionate, creative people. We’d love you hear your ideas for a tree project in your community. To help get you started, we assembled a few examples. There’s no need to limit yourselves to one category. A project may mix elements of all four categories or just one or two. Add your own ideas to reflect the unique neighborhood where you are working.  

We are looking for projects that meet the following broad goals: 

• Growing | We love to plant trees! Growing projects might install new trees in public spaces, convert hardscape to natural parkland, or restore damaged ecosystems to allow natural renewal of seedlings.  

An Urban Forest Grant was used for growing new, high-priority canopy at Alderbrook Pocket Park. 

Get inspired! View all growing category projects since 2015. 

• Caring | Trees need care to reach their full potential. Caring projects might include pruning existing trees to develop a strong structure, adding mulch to root zones so trees can survive in tough Texas weather, irrigating dry areas to support trees struggling through drought, or treating trees to protect them against disease or insect problems. 

Grant funds are caring for the Auction Oaks in Republic Square via soil improvements and mulch.

Get inspired! View all caring category projects since 2015. 

• Informing | Most people enjoy the shade of a tree on a hot day and pretty flowers in spring, but not everyone understands what trees need to survive and thrive. Informing projects help people learn about their trees and how to support them through a range of challenges. 

A teacher from Partners for Education, Agriculture, and Sustainability (PEAS) informing two young students about ecosystems.

Get inspired! View all informing projects since 2015.

• Inspiring | We’ve all heard that a picture is worth a thousand words. Inspiring projects spark a new awareness of trees and what they need. This might include an art installation (like Thirst, Stickwork or Fortlandia), a tree-themed poetry contest, or signage in public spaces to help people understand important tree concepts.  

“Stickwork,” an art installation by Patrick Dougherty, created outdoor spaces from invasive privet branches to inspire reflection about our environmental impact. Photo by Aimee Aubin. 

Get inspired! View all inspiring category projects since 2015. 

Before developing your project and filling out an application, reach out to the Urban Forest Grant manager to ensure your project meets urban forestry goals. Please note that application deadlines are every January 1 and July 1. To learn more, please visit https://austintexas.gov/page/urban-forest-grant.  

Investing development fees

In Austin, we know trees are important to public health and quality of life. We try hard to preserve and protect our urban forest. We also try to reduce urban sprawl by building dense neighborhoods where people live close to work and shopping. The challenge is to strike a balance between these goals. Our Tree Ordinance is our primary tool for compromise between trees and development. 

The City Arborist Program reviews permit requests for impacts to regulated trees. When regulated trees are removed, mitigation fees are often required by ordinance. The Urban Forest Grant invests this money in projects that will benefit our trees and community for generations to come. 

Article by Keith Babberney, Education Forester 

This information is sponsored by the City of Austin. Learn more about trees and resources at the Tree Information Center! 

www.austintexas.gov/trees  

Trees have always been an important part of the character of Austin. We have special trees where we mark important historical events. We love to enjoy the pecans at Barton Springs on a sunny day. We will park half a mile from the store if we can leave our car under a shade tree while we shop. We cannot take our trees for granted. If we want to continue enjoying a healthy urban forest in coming decades, we need to start planning now. Climate forecasts predict significant changes in our average temperatures, rainfall, and major weather events. Our existing trees may struggle to adapt and survive in the new conditions.

Experts predict higher summer temperatures in our area in future decades.

Change is Coming

Climate experts predict there will be significant changes in our area for the foreseeable future. The City of Austin partnered with the United States Department of Agriculture (USDA) Climate Hubs in 2020 to assess the vulnerability of Austin’s urban forests and natural areas to climate change. The USDA report warns we will see increases in temperature of five to ten degrees Fahrenheit over the next century. Rainfall patterns may vary seasonally from what we historically have expected. As a result, our favorite plants may struggle to survive. We will probably see a change in the hardiness zone for our region. Some tree species will be better able to adapt to these changes than others.

City land managers are already taking climate changes into account in their decisions. Often, this involves large projects with big budgets. For people who want to help but don’t have resources for major projects, there are some simple steps to apply. Below are some ideas we can all use in our own lawns and neighborhoods. If we work together, future generations of Austinites will be able to enjoy the continuing benefits of a healthy urban forest.

What can we do?

There are simple ways to help preserve our urban forest that don’t require a huge effort or expense. These are things we already do, for the most part. The goal now is to be more aware and deliberate about doing them consistently. Changes to our climate should guide us as we manage existing sites and plan for new development. Below are some goals to consider, and some strategies that can help us reach them.

Increase diversity

We love to plant trees, but we need to be thoughtful about what species we choose. Diversity of species, lifespan, and mature size are all important. The species we choose should be native to the site or adaptable to the conditions there. Sometimes, we may have to guess how a given tree will respond to hotter, drier weather or how it can handle the type of soil where it is planted. Our goal as we move forward should be to try a range of species, even within the same site. This will increase our chances that at least some of the trees we plant will be successful over the long term.  

Here are some ways to take diversity into account as we plant new trees and landscapes:

• Avoid planting the most common species nearby. If every tree in an area is the same species, we risk losing them all to one problem as stressful conditions become more prevalent. For example, some northern cities lined their streets with American elms, then lost them all to Dutch Elm Disease in the 1970s. They replanted with only ash trees. Then they lost all of these trees to Emerald Ash Borer in the early 2000s. Planting a diverse mix of species would allow us to avoid this same mistake. If an outbreak of disease or pests occurs, we can retain some tree benefits while we replace any lost or damaged specimens.

A street in Ohio was lined with healthy ash trees in 2006. In 2009, they were all killed by emerald ash borer. Photos by Daniel A. Herms, The Ohio State University.

• Choose new species from places where soil and other conditions are similar. A tree that thrives along the banks of a stream or river will probably struggle on a rocky hilltop. Species that have flourished in areas similar to your site conditions will have a good chance to survive there. Of course, with the hotter climate, they still might struggle. Look to hotter, drier places with the same soil type and conditions for species that can tolerate the changes. There is risk inherent in this strategy, unfortunately. The species we bring from other places could become invasive and crowd out the plants that historically have grown here. We will need to monitor results carefully and develop new species recommendations as we see how different trees perform.  
• Create communities of plants instead of isolated specimens. Plants often form harmonious relationships together. For example, we often see landscapes with post oak, blackjack oak, and yaupon holly all growing in the same area. If we look at hotter climates with yaupon holly, we might find another species of tree that commonly grows near yaupon but isn’t common in Austin. We can develop these new communities locally in hopes that the new trees will perform well as our climate heats up.

Water during droughts

Trees are well adapted to storing resources to help them survive difficult conditions, but they have limits. Extended droughts take a heavy toll on trees. To avoid damage during long periods with no rain, it is important to give trees a long, slow soaking, even in yards with automatic sprinkler systems. The short, frequent intervals that keep grass looking good are not usually enough to help trees. Young trees might need additional water each week. Mature trees can usually get by with monthly irrigation, provided it soaks into the soil at least several inches deep. Adding a layer of mulch around trees helps retain moisture so we can water less often (see "Tree care" below).

Soaker hoses can help trees survive drought conditions efficiently, especially when topped with mulch.

Keep your leaves in autumn

In a forest, the ground is covered with fallen leaves and other dead plant material. As it decays, it improves soil health and structure. When we remove all the leaves from a suburban lawn, our soil suffers. It’s good to rake leaves off turf grass, but keep them on your property. When raked underneath trees or shrubs, the leaves will blanket the soil and protect plants from extreme temperatures. If you are concerned they will blow back onto the grass, they can be composted in a bin or other container and used to feed the soil after they decompose. 

Tree care

Planting new trees is great, but we must care for our existing trees to have a healthy urban forest. We can improve the health of most trees by protecting and improving their soil. A tree with healthy roots can better defend itself against pests, diseases, or environmental stress. This means we can avoid chemical applications that might damage sensitive ecosystems. 

Adding compost to root zones twice a year improves the soil and helps roots thrive. Maintaining mulch beds under trees and other plants helps protect them against heat and drought while also improving soil. It can be hard work, but it’s inexpensive and requires only basic skills and equipment. It’s a good idea to test the soil in case other amendments are needed. A qualified arborist can explain the different options and their cost. 

Even small mulch rings help protect trees against drought and temperature extremes. 

Structural pruning

Why do some trees break in storms, while others come through them fine? We can never control every factor, but arborists have learned to identify warning signs that a tree is more likely to fail. Proper pruning while trees are young can reduce the chance they will break in old age. This saves tree canopy for shade and wildlife, reduces injuries to people and property damage, and provides significant benefits to our environment. Most young trees need up to 25 years of regular structural pruning to develop a strong, permanent structure. 

A forest for the future

These are some simple ideas that can preserve our urban forest for future generations. If you would like to consider more ambitious projects, you can learn how at the USDA’s site. If we all remember to consider these strategies as we care for our homes and neighborhoods, future Austinites will have a healthy urban forest to enjoy for decades to come.

Article written by Keith Babberney, Education Forester for the Development Services Community Tree Preservation Division, City of Austin.

Visit the Tree Information Center at www.austintexas.gov/trees.  

Our Urban Forest Grant program was developed to maintain, restore, and replenish our urban forest using development fees accrued via the tree preservation ordinance. Today, we are shining a spotlight on one exemplary project that helps us meet the goal of creating a sustainable, equitable urban forest for all our city’s residents. At Roy G. Guerrero Colorado River Metro Park, local non-profit Ecology Action has been working for years to restore a degraded site back to the forest it once was. 

Ecology Action has developed hiking trails for access to the restored forest at Guerrero Park. 

Restoring a forest

Located in the Montopolis neighborhood near the Colorado River, the project at Roy G. Guerrero Colorado River Metro Park and Circle Acres Nature Preserve is helping to bring access to nature for an area that desperately needs it. Austin has a goal of making it possible for all our residents to live within a reasonable range of green space. Montopolis is a high priority area because such access has been limited there for a long time. This site was used by ranchers and dairy farmers decades ago, converting native forest to pastureland. It was later used as a City landfill for many years, then continued to be an illegal dumping site long after Grove Landfill was officially closed.  

Signs educate visitors about the site history and restoration. 

The bulk of Ecology Action’s work has been to restore Circle Acres, which they purchased to rebuild and protect it. Volunteers laboriously excavated tons of old garbage and other waste from the site, including almost 1,000 used tires. Today, it is transformed, with new trees and plants being added annually and a hiking trail where people can see the improvements that have been made. Interpretive signs help educate the public about the project and its recovery back to a diverse ecosystem. Restoration of this site has turned a trash dump into a nature preserve. Residents and visitors have more access to green space in an area where opportunities have been scarce. 

This aerial view of the park from the 1940s has been overlaid with dots showing where Ecology Action has planted new trees over several years.

Caring for trees

The work Ecology Action has done extends beyond just plants and trails. They have purchased and installed several water storage tanks that allow them to ensure the new trees don’t suffer during dry weather. City watering crews help keep the tanks filled so trees can be irrigated as needed. In addition, Ecology Action installed greenhouses where they grow native plants to restore and enhance the original ecosystem. Staff and volunteers hand water the new plants and trees at first to help them become self-sustaining.  

Water storage tanks allow Ecology Action to irrigate new plants and trees until they can become self-sustaining. 

Growing new Trees

In the greenhouses, spent mushroom blocks from the produce industry are combined with wood chips and other natural materials to create a medium for growing seeds until they are ready to be planted in the landscape. The greenhouses nurture local standbys like Mexican buckeye, Eastern Gamagrass, and other native grasses. Live oaks are also part of the mix, but not just any live oaks. “We source acorns to grow from the heritage trees located in the park nearby, some of the oldest trees in Austin,” Paulus said. 

“There are several huge, old cottonwoods along the creek, but they are not able to establish young cottonwoods naturally because of all the deer,” said Eric Paulus, Ecology Action Operations Director and Land Manager. “We grow cottonwood saplings from the local seed, then plant them with cages so we can ensure future generations have cottonwoods in this park, too.” 

Replacing rare plants for biodiversity 

To create a more sustainable ecosystem, Paulus also nurtures rare Texas plants, including some that are native to hotter, drier climates. This includes small trees like green hawthorn, red buckeye, and Texas ebony, and large species like black hickory. “We get a lot of help from the LBJ Wildflower Center sourcing a diverse mix of seeds,” said Paulus. Diversity in new plantings increases the chances of having a healthy ecosystem even when some species may struggle to adapt to changing weather patterns. 

Eric Paulus shows the growing medium he makes from recycled mushroom spawn and worm castings to support seeds until they can be planted in the park and preserve. 

Create your own project

Through the efforts of a local non-profit and its volunteers, a degraded forest is being restored and expanded to allow Austin residents and visitors to enjoy natural spaces for decades to come. We are proud to support their work through our Urban Forest Grant. We hope the ambitious work at Circle Acres Nature Preserve can be a source of inspiration for other local groups seeking to apply for similar projects, whether big or small. Visit our web site to learn how to get funding for your project that will help our urban forest. 

Article written by Keith Babberney, Education Forester for the Development Services Community Tree Preservation Division, City of Austin. 

Visit the Tree Information Center at www.austintexas.gov/trees.