Kate Sessions Commitment is a nonprofit organization dedicated to advancing canopy, community and climate action in the City of San Diego. Our objective is to grow our urban forest not by planting trees, but by supporting their growth through science and community partnerships.
To keep our urban forests healthy, we have to know what trees and communities need.
There are many factors that influence the health and longevity of urban trees. Some are biological, such as soil condition and species size. Others are social, like the type and amount of care provided to trees once planted. This complex field of study, the science of tree establishment, has been a topic of interest to the Kate’s Trees team. A literature review outlining factors that influence tree growth in the initial years after planting was conducted by our team: the Tree Establishment Literature Review. Read more details in these two articles, Golden Shovel: Successful urban tree planting initiatives and Socio-ecological approach to tree stewardship
San Diego’s Local Context: trees are planted, then what?
Lots goes into growing a tree. Young tree health depends on interrelated factors that include soil and other site characteristics, species selection (including drought-tolerant and climate-adapted species), nursery stock quality, young tree pruning, and water availability during and after project funding. Tree success is far greater when trees are planted in parks and areas with irrigation, and adjacent to front yards that are irrigated. Improved tree establishment success can be gained by mapping and field work to monitor tree conditions and the environmental factors that influence those tree conditions, then evaluating and adapting local best practices for trees.
Kate Sessions Commitment completed San Diego’s first public tree condition survey and report in 2025, followed quickly by two more. These tree condition surveys have collectively assessed the health and environmental context of over 1,000 street trees in San Diego. The results from these surveys informed our literature review as it connects to San Diego’s local context. Read the reports here..
We Need Trees, and Trees Need Us
When young trees are planted into their urban forever homes, they enter the most vulnerable phase of their lives. This ”establishment phase” is when young trees are most vulnerable to the stressors of the urban environment, such as soil quality and compaction, planter size, and availability of water. They are also more susceptible to vandalism and vehicular damage because of their smaller size. That is why our attention and continued investment are needed once trees are planted in our communities.
In order to grow past this vulnerable phase, young trees need CARE. Primarily, recently planted trees need water. The City of San Diego follows a basic watering regimen for all street trees, which lasts three years. Even so, unirrigated trees like street trees are often stressed, stunted or even dead after three years. Regular mulching (twice a year) and supplemental watering (weekly during dry months) can protect trees from drought stress and allow them to grow large enough to provide the benefits we love them for. This is something we can ALL do to improve the life of our trees and, in turn, our community.
Now is the time to Grow Trees Together.
Urban and community foresters around San Diego have been working hard to expand our urban forest, but tree canopies expand not just by planting, but also by increasing tree health through community engagement. Thousands of trees have been planted across the city, with more on the way; there may even be young trees in your area. Join us as we care for these young trees, monitor their health and lift community voices to advocate for innovations, collaborations and civic engagement in the urban greening world.