- Author: Judy Quan
Editor's Note: This blog post originally appeared on the Master Gardener Program of Alameda County website.
Thinking of planting a street tree?
Do you have space for a tree in the parking strip, that no man's land between the sidewalk and the street? If you do, there are many advantages to having trees grow in that space.
Why plant a tree?
- Trees are beautiful and welcoming. Trees have a calming and healing effect on people and community. They add value to the neighborhood.
- Trees help us to live with warming temperatures. Street trees, part of the landscape, help to reduce the effect of urban heat islands by providing cooling shade to sidewalks, buildings and other structures that capture heat.
- Trees fight climate change. Trees absorb and store carbon dioxide, also reducing greenhouse gas emissions to the atmosphere.
- Trees add to the natural habitat. They can provide habitat for birds, pollinators and other wildlife.
- Trees improve the local environment. They provide windbreaks, capture storm water runoff and muffle urban noise, among many other things.
“Unfortunately, their [street trees'] average lifespan in our cities is less than 1/4 of their potential due to poor selection and care.“ Janet Hartin, Environmental Horticulturist, UC Cooperative Extension, Trees for Tomorrow Start Today
Tips on Street Tree Selection
Gather information about the site (your parking strip)
- Check with the city. Find out whether the homeowner is allowed to plant a tree. In some cities, only the city can plant in the parking strips.
- Power lines? You need to determine whether the power lines are on your side of the street or not. If they are, then you are limited to small trees that are "ok" to plant under the high voltage lines.
- Width of parking strip? Then you will need to measure the width in inches of the parking strip where you are planning to plant your tree. Then you can compare your dimensions to those of the suitable tree basin width.
- Other considerations? Think about the type of soil you have, the availability of water, shade, proximity to buildings, and wind conditions.
Look around in your neighborhood to see what you like and don't like in street trees.
- Seeing a mature, full-grown specimen of a particular species of tree in your neighborhood is very different from seeing a photo of the tree on the internet. Often the in-person view will give you a really good feel for a tree's true appearance and it may also show you other aspects such as the amount of litter from flowers, seeds and leaves.
- Talk to your neighbors about the trees in your neighborhood.
- As you drive or walk around the city, look around at the street trees and take note of the ones that you like and where they are located.
- If your city has a public works department, parks department or an urban forester, you may be able to get help with the identification of the trees and may also get recommendations.
What trees are approved for street trees in your area?
- Many cities, but not all, have an approved list of street trees. These are the trees that are officially approved for planting in the parking strip. The list often has additional information as to how to select trees for a particular site.
- Many cities have an urban forester who manages the selection and care of tree populations in the urban setting. Often the forester may be part of public works or parks division of city programs. Sometimes there are programs that promote tree planting and financial incentives might be available.
- Local tree lists and planting information for some of the cities of Alameda County. Please contact your city hall or public works for information in your city.
Unincorporated communities of Ashland, Castro Valley, Cherryland, Fairview, San Lorenzo, and Sunol
What are the characteristics of the trees on your list?
- Research both the common name and the botanical name, so you will get more information on the tree including information on litter issues, root damage potential and mature size.
- Trees are either deciduous (lose their leaves in the fall) or evergreen (keep leaves/fronds/needles year-round). Just because a tree is evergreen, does not mean that you don't have leaf litter. Evergreen trees may drop some leaves more-or-less year around instead of the once-a-year leaf drop in the fall.
- Once you have narrowed your list down to a few trees, you might give the city a call and find out if there is information on where you can see that type of tree locally.
- Minimize potential damage to the sidewalk. To avoid or minimize sidewalk/curb damage/lifting, choose a smaller tree that fits your parking strip and be sure to water the tree appropriately.
Care of trees … things I wish I had known
Unfortunately street trees are sometimes not planted with the ideal tree selection/planting guidelines. Fortunately, many of these problems can be corrected if noticed early on, soon after the tree has been planted.
Here are some practical tree care tips from Janet Hartin, a UCCE horticulturalist.
Trees for Tomorrow Start Today
How to Avoid Common Ailments of Landscape Plants
You may find that you will use this information on care of trees directly if you end up planting your own tree, or you might find that you will use the information to make sure your tree is planted correctly by the city/contractor hired by the city.
4 Tips on Planting trees
- Plant the tree in native soil, with NO amendments or compost.
- The hole for the tree should be the same depth as its container and at least 2-1/2 times wider. Make sure that the flare of the crown is above ground. Remove the soil, gently place tree in hole, fill with original soil around the plant.
- Prevent circling and kinked tree roots. Straighten or cut off circling or kinked roots. Roots circle or become kinked when there is no space for roots to grow out, such as in containers or small plant holes or organic-filled plant holes. When holes are filled with organic material, roots may never grow beyond the boundaries of the original hole because the roots prefer the richer organic material.
- Check/remove the tree ties or stakes. Remove any tree ties that are too tight and cut into the tree trunk or branches. Tree ties should be loose enough so that your tree can sway with the wind. This movement allows the trunk of the tree to develop more strength and flexibility over time. The ties and stakes may be removed as the lower trunk becomes stronger and self-supporting. Find more detailed information about when to remove ties and stakes here:
- Apply mulch 2-4 inches deep around your tree. Keep all plants and mulch several inches away from tree trunks.
8 Tips on Watering Trees
- Keep tree trunks dry. They should not come into contact with water from sprinklers or hoses.
- Apply the right amount of water at the right time.
- Water newly planted trees regularly for a full season Many newly transplanted landscape trees die from the soil drying out too much between waterings. Regularly water newly planted trees. The tree root systems are small and need to be kept moist for a full growing season.
- Water the newly planted, drought-tolerant species too. This schedule of regularly watering newly planted trees holds true for drought-tolerant species as well as those that require more water. Once plants become well-rooted they should be watered less often but for longer periods of time.
- Water halfway to dripline and beyond. Since tree roots spread outward as well as downward, water should be applied beyond the dripline of the tree, if possible.
- Most established trees need water too. Most trees in California need supplemental irrigation above and beyond the naturally-occuring rains, especially in times of drought. Water established trees less often but more deeply to encourage deep rooting and structural balance above and below ground.
- Trees need to be watered slowly and deeply. If you use a garden hose, apply the smallest trickle of the water slowly, moving the hose every few hours to water the entire area around the tree. The deep watering encourages roots to grow downward and help prevent sidewalk damage.
- Do NOT water trees on the same irrigation/drip system as the one used for lawns and groundcovers. The light, frequent watering every few days that is appropriate for lawns/groundcovers discourages the deep growth of tree roots.
Tip on Pruning Trees
Prune trees only as needed and avoid topping them. Hire a credentialed and knowledgeable arborist to correctly care for your trees. Find a list of International Society of Arboriculture Certified Arborists in your area here.
Thinking about tree selection and predicted future climate change
You might select trees that are more suited for the future warming trends. Here is a very interesting article from the UCANR Green Blog on using location for time. For instance, in 2099 the climate in Berkeley may be more like that of Santa Ana.
“Urban foresters in inland cities of California should begin reconsidering their palettes of common street trees to prepare for warmer conditions expected in 2099 due to climate change,” said the study's co-author, Igor Lacan, UC Cooperative Extension environmental horticulture advisor in the Bay Area.
Street trees are important in so many ways:
Trees provide beauty and calm, help us to live with warmer temperatures, fight climate change, provide a natural habitat for wildlife including birds and pollinators. It is important to properly select, plant and care for street trees, so that the benefits of each street tree can be realized to its full potential.
Still need help?
Confused or need more information? Email us at acmg@ucanr.edu. Or contact us through our website.
More resources on the importance of trees, tree selection, tree care:
Four articles with more details on tree selection and tree care from Janet Hartin, UCCE horticulturalist:
- Trees for Tomorrow Start Today
- How to Avoid Common Ailments of Landscape Plants
- Landscape Tree Irrigation 101
- Plant a Tree. Leave a Legacy!
If you want more details of how to plant a tree with photos, here is a good source: “Save the Planet, (Learn How to) Plant a Tree” by Dr. Linda Chalker-Scott who is an ISA certified arborist and an ASCA consulting arborist. She is also WSU's Extension Urban Horticulturist and a Professor in the Department of Horticulture.
The importance of trees to cool urban heat islands
Lush urban forests can help communities face climate change
Trees also can have calming and healing effect on people and community
Cities in California inland areas must make street tree changes to adapt to future climate
Cooperative Extension San Joaquin County
Really good source of information on arboriculture and getting the most benefit from trees through good management.
UC study seeks street trees that can cope with climate change
- Author: Pamela S Kan-Rice
A free webinar series titled “Trees to the Rescue: Solutions for Climate Change” will be held on May 14-16, from 4 p.m. to 5:30 p.m. each day. The webinars are sponsored by the University of California Thelma Hansen Fund.
“The webinars aim to increase our understanding of the role of trees in mitigating and adapting to climate change, how to plant the right trees and keep them healthy in urban environments, and the challenges of increasing the number of trees at the local level,” said Annemiek Schilder, director of Hansen Agricultural Research and Extension Center, who is organizing the series. Hansen REC is operated by UC Agriculture and Natural Resources.
Participants will discuss some of the challenges and pitfalls of reforestation, urban greening and tree equity. They will also provide diverse perspectives on tree planting and maintenance efforts and policy at the local level.
“Anyone interested in learning about the importance of trees in urban environments and climate resilience, as well as tree retention in the landscape should join us,” she said.
The agenda for each 90-minute webinar is listed below. To register, visit https://bit.ly/HansenTreesWebinar.
Tuesday, May 14: Trees as a Tool for Climate Change Mitigation and Resilience
4 p.m. Welcome—Annemiek Schilder, Director of Hansen Agricultural Research and Extension Center
4:05 p.m. Opening Remarks—Matt LaVere, Ventura County Supervisor District 1
4:10 p.m. Improving Outcomes of Tree Growing and Forest Restoration Efforts—Karen Holl, Professor of Environmental Studies, UC Santa Cruz
4:50 p.m. Climate Resilience through Urban Greening—Edith de Guzman, UC Cooperative Extension Specialist, Water Equity and Adaptation Policy, UCLA
5:30 p.m. Closing—Annemiek Schilder
Wednesday, May 15: Optimizing Tree Survival in a Changing Climate
4 p.m. Welcome—Emma Volk, Production Horticulture Advisor, UCCE Ventura and Santa Barbara counties
4:05 p.m. Cooling Urban Heat Islands with Climate-Resilient Trees—Janet Hartin, Environmental Horticulture Advisor, UCCE Los Angeles and San Bernardino counties
4:30 p.m. Keeping Trees Healthy from Sapling to Maturity—James Downer, Environmental Horticulture and Plant Pathology Advisor Emeritus, UCCE Ventura County
5:05 p.m. Dealing with the Inevitable Threat of Exotic and Invasive Pests—John Kabashima, Environmental Horticulture Advisor Emeritus, UCCE Orange County
5:30 p.m. Closing—Emma Volk
Thursday, May 16: Tree Advocacy and Planning at the Local Level
4 p.m. Welcome—Julie Clark, Natural Resources Community Education Specialist, UCCE Ventura County
4:05 p.m. Native Tree Restoration with Partners and the Public—Joey Algiers, Restoration Ecologist, Santa Monica Mountains National Recreation Area
4:30 p.m. Panel Discussion (Joey Algiers, moderator):
- Joey Algiers, Santa Monica Mountains National Recreation Area
- Mireille Vargas, County of Ventura Sustainability Division
- Mikaela Randolph, Green Schoolyards America
- Jan Scow, Registered Consulting Arborist, Ojai Valley
- Max Young, Ventura Regional Fire Safe Council
5:30 p.m. Closing—Julie Clark
- Author: Pamela S Kan-Rice
A free webinar series titled “Trees to the Rescue: Solutions for Climate Change” will be held on May 14-16, from 4 p.m. to 5:30 p.m. each day. The webinars are sponsored by the University of California Thelma Hansen Fund.
“The webinars aim to increase our understanding of the role of trees in mitigating climate change, how to plant the right trees and keep them healthy in urban environments, and the challenges of increasing the number of trees at the local level,” said AnnemiekSchilder, director of Hansen Agricultural Research and Extension Center, who is organizing the series. Hansen REC is operated by UC Agriculture and Natural Resources.
The agendas for each 90-minute webinar are listed below. To register, visit https://surveys.ucanr.edu/survey.cfm?surveynumber=42636.
Tuesday, May 14: Trees as a Tool for Climate Change Mitigation and Resilience
4 pm Welcome—Annemiek Schilder, Director of Hansen Agricultural Research and Extension Center
4:05 pm Opening Remarks—Matt LaVere, Ventura County Supervisor District 1
4:10 pm Improving Outcomes of Tree Growing and Forest Restoration Efforts—Karen Holl, Professor of Environmental Studies, UC Santa Cruz
4:50 pm Climate Resilience through Urban Greening—Edith de Guzman, UC Cooperative Extension Specialist, Water Equity and Adaptation Policy, UCLA
5:30 pm Closing—Annemiek Schilder
Wednesday, May 15: Optimizing Tree Survival in a Changing Climate
4 pm Welcome—Emma Volk, Production Horticulture Advisor, UCCE Ventura and Santa Barbara counties
4:05 pm Cooling Urban Heat Islands with Climate-Resilient Trees—Janet Hartin, Environmental Horticulture Advisor, UCCE Los Angeles and San Bernardino counties
4:30 pm Keeping Trees Healthy from Sapling to Maturity—James Downer, Environmental Horticulture & Plant Pathology Advisor Emeritus, UCCE Ventura County
5:05 pm Dealing with the Inevitable Threat of Exotic and Invasive Pests—John Kabashima, Environmental Horticulture Advisor Emeritus, UCCE Orange County
5:30 pm Closing— Emma Volk
Thursday, May 16: Tree Advocacy and Planning at the Local Level
4 pm Welcome—Julie Clark, Natural Resources Community Education Specialist, UCCE Ventura County
4:05 pm Native Tree Restoration with Partners and the Public—Joey Algiers, Restoration Ecologist, Santa Monica Mountains National Recreation Area
4:30 pm Panel Discussion (Joey Algiers, moderator):
- Joey Algiers, Santa Monica Mountains National Recreation Area
- Mireille Vargas, County of Ventura Sustainability Division
- Mikaela Randolph, Green Schoolyards America
- Jan Scow, Registered Consulting Arborist, Ojai Valley
- Max Young, Ventura Regional Fire Safe Council
5:30 pm Closing— Julie Clark
- Author: Janet S Hartin
To date, over 1,800 climate-ready shade trees and tips on their planting and long-term care have been provided by UC Master Gardeners and over 20 partners to residents of low shade neighborhoods in San Bernardino and Riverside Counties through the “Trees for Tomorrow Start Today” project. Tree species given away are identified from research projects including the joint University of California/United States Forest Service (USFS) study at UC Riverside as well as from other research, local observations, and input from the green industry and academic colleagues.
Why is this project so important? 95% of Californians now reside in cities and suburban environments. Resulting urban heat islands created by built environments coupled with impacts of climate change can be mitigated through nature-based solutions. Planting climate-ready shade trees now will help ensure cooler urban areas in the next several decades as trees mature and maximize their urban ecosystem benefits. Fortunately, the shade from a single well-placed tree can decrease surface temperatures of black asphalt and artificial turf by more than 70 degrees F in hot inland and desert cities. Studies show that surrounding air temperatures can also be reduced through the transpiration process.
A major goal of the"Trees for Tomorrow Start Today" project is to enhance tree canopy cover in low shade neighborhoods also plagued with much higher than average levels of air pollution and pulmonary and cardiovascular disease incidence. Events over the past month have occurred in Fontana, San Bernardino, and the Salton Sea.
Thank you to all our partners and, especially, our tree recipients, for greening and cooling your yard and neighborhood!
- Author: Patty Guerra, UC Merced
Water is among the most precious resources on the planet. Some areas don't get enough; some get too much. And climate change is driving both of those circumstances to ever-growing extremes.
Two UC Merced experts in civil and environmental engineering took part in a recent report by the Environmental Defense Fund examining the issue and potential solutions. Associate Professor of Extension Tapan Pathak and Professor Josué Medellín-Azuara co-authored the report, "Scarcity and Excess: Tackling Water-Related Risks to Agriculture in the United States," and wrote the section pertaining to California.
In addition to climate change, disruptive human interventions such as groundwater over-extraction, sprawling drainage networks and misaligned governance are driving up water-related agricultural costs, particularly in midwestern and western states, the researchers found.
The problem is magnified in California, which hosts the largest and the most diverse agricultural landscape in the U.S., Pathak and Medellín-Azuara wrote, with gross revenues from farms and ranches exceeding $50 billion.
"Due to the favorable Mediterranean climate, unique regional microclimate zones, a highly engineered and developed water supply system, and a close connection between producers and research and cooperative extension institutions, California's agricultural abundance includes more than 400 commodities, some of which are produced nowhere else in the nation," the UC Merced researchers wrote.
But the state's varying climate and water needs pose a challenge. Though most of the precipitation falls in the northern part of California, the southern two-thirds of the state account for 85% of its water demand. And all of those crops must be watered in the summer, when there is little, if any, rainfall.
Some of the water comes from snowpack developed through winter storms and stored in reservoirs as it melts. Much of it comes from the Colorado River.
"Substantially less water is captured and stored during periods of drought, imperiling California's water supply and putting agricultural water needs at risk," Pathak and Medellín-Azuara wrote.
Climate change, with increasing periods of drought between excessively wet winters, magnifies that risk.
"Further, the rate of increases in the minimum temperatures in the Sierra Nevada is almost three-fold faster than maximum temperatures, resulting in potential decrease in the snowpack, earlier snowmelt, and more water in liquid form as opposed to snow," the researchers wrote. "According to the California Department of Water Resources, by 2100, the Sierra Nevada snowpack is projected to experience a 48% to 65% decline from the historical average."
Climate change is also expected to affect the availability of water from the Colorado River.
Climate extremes such as heat waves, drought and flooding - giving rises to increased weeds, pests and disease - are already significantly impacting agriculture and the broader economy, Pathak and Medellín-Azuara wrote.
The state's drought from 2012 to 2016 led to about 540,000 acres of fallow farmland in 2015, costing the state's economy $2.7 billion in gross revenue and 21,000 jobs. With the lack of precipitation, farmers increasingly pumped groundwater to irrigate crops, depleting those resources.
The report goes on to recommend policies, programs and tools be developed for agricultural resilience, including:
- Changing land use and crop management practices to support a transition to an agriculture footprint that can be sustained by the available water supplies.
- Increasing farmer and water manager access to important data and innovative technological tools to support their efforts.
- Reimagining built infrastructure and better using natural infrastructure so regions are better equipped to handle weather extremes.
- Developing policy and funding mechanisms to support mitigation and adaptation to water-related risks, avoid maladaptation and ensure food and water security.
"California's innovative agriculture needs to rapidly adapt to more volatile water availability, climate-driven higher water demands, and regulation protecting groundwater reserves, communities and ecosystems," Medellín-Azuara said. "The early adoption of more sustainable practices in agriculture will likely pay off dividends both in the short and long terms."
Added Pathak, "California faces significant challenges related to climate change, but it also presents opportunities for innovations, collaborations and sustained growth. To make agriculture resilient to climate risks, we need to engage in holistic solutions that integrates environmental, social, economic and policy considerations."