Factsheet: Tree monitoring

Does your community want to ensure that its trees thrive over the long term? This factsheet explains why tree monitoring is an essential part of your planting project, and how to set up an effective monitoring program. Learn about the expertise, tools and technology that you’ll need to collect accurate data to inform tree maintenance. 

  Why monitoring trees matters for project success

Planting trees provides many benefits to communities, from cooling neighbourhood streets to restoring habitat and enhancing biodiversity. However, planting trees alone is not enough to ensure these benefits. Trees planted in urban areas face many challenges to their long-term health and survival, including drought, vandalism, pests and disease. While the first few years after planting are often the most critical, consistent monitoring even after trees are established is essential.

To ensure that your tree planting project is successful and to protect your investment of time and resources, it’s important to monitor both the trees and the areas where they have been planted. A structured monitoring program informs tree maintenance practices, ensuring that your community’s trees receive the care they need to thrive over time.

How monitoring guides tree maintenance

Effective monitoring helps detect signs of stress, such as premature leaf drop, yellowing leaves (called chlorosis) or damage to leaves and stems. These symptoms can be caused by different factors, including pests, disease, drought and nutrient deficiencies in soil.  

Monitoring also helps spot structural problems that can make a tree unstable or cause it to fail as it matures if they are not addressed. These issues include leaning trunks, uneven growth, weak branch attachments or girdling roots (roots that wrap around the trunk).  

Identifying stress or structural problems early can help you adjust your maintenance strategies and plan targeted interventions. Actions like corrective pruning, watering, soil amendments, staking adjustments or root collar excavations can improve tree health and reduce the risk of long-term issues. For example, if a young tree is leaning, staking can be introduced or adjusted during routine maintenance to help straighten it.

In cases where trees do not survive, monitoring gives you a consistent record of tree health, structural conditions and maintenance activities. This information can provide valuable insights into what went wrong, helping you adapt future planting strategies to improve survival rates and maximize the impact of your tree planting projects. 

How to set up a monitoring program

 Assign responsibility for monitoring

Tree monitoring responsibilities should be clearly assigned during the planning phase of a project and matched with the skillsets of those tasked with monitoring activities. Technical professionals like foresters, ecologists and arborists are best suited for more specialized tasks, like measuring multiple growth and health indicators, assessing tree structure and risk, and deciding what interventions are needed when issues are identified. If your municipality does not have this expertise in-house, consider seeking consultant services or partnering with a local university or research team.

Community groups and individuals can also play an important role in monitoring if they are given adequate training. Community members are often invested in the success of tree planting projects. They are closest to the site and can observe problems the earliest. With simple training and tools like mobile tree inventory apps, calipers, long measuring tape, and diameter at breast height (DBH) tape, they can track survival rates, detect early signs of stress, measure tree growth, and report issues like pest outbreaks, vandalism or animal damage.

Combining professional expertise with community engagement and accessible tools makes tree monitoring more sustainable and effective. 

Case study: Forest Health Ambassador Program 

Since 2014, the Town of Oakville, Ontario, has partnered with private consulting firm Bioforest to train local volunteers to identify signs and symptoms of invasive pests through the Forest Health Ambassador Program. Volunteers receive targeted training to monitor trees for infestations of emerald ash borer, spongy moth and Asian long-horned beetle, species that pose serious threats to urban forests with significant budgetary and management implications.

This low-cost program leverages community interest in urban forest stewardship, significantly expanding the town's monitoring capacity beyond what the municipal budget would typically allow. It serves as a strong example of how community members can be meaningfully engaged in long-term urban forest health monitoring to support early pest detection and timely intervention.

Create monitoring schedules  

Establishing an appropriate schedule is key to effective monitoring. The frequency of monitoring should balance your project’s goals, resources and the life stage(s) of the trees.  

• Early monitoring: Trees are most vulnerable in the first three to five years after planting, so more frequent monitoring of young trees is recommended. This might include checks every one to two months after planting to quickly identify and address issues.

  If the same individuals or teams are responsible for both early maintenance tasks (like watering, mulching, pruning or weeding) and monitoring, it can be efficient to carry out these activities concurrently where monitoring dates line up.

• Ongoing monitoring: After the initial establishment phase, monitoring can take place less often. Annual visits are often enough to track the long-term growth, health and structure of planted trees, although this can be done less often if trees are tracked in a regularly updated inventory (e.g., every five to ten years). For trees on public lands, consider setting up online reporting portals or phone lines for residents to report concerns. If you are setting up a community-based monitoring program, residents can also upload the data they collect about the trees.
• Environmental monitoring: Apart from the trees themselves, it is important to monitor site conditions and check for invasive species at least once per year, ideally during the growing season or after significant weather events.
• Adaptive scheduling: Monitoring plans should remain flexible. If unexpected problems arise, such as widespread mortality or the discovery of a particular pest or disease, you may need to monitor planting sites more frequently.

Your monitoring schedule should consider resource availability, including personnel, equipment and funding. More frequent monitoring can provide richer data but it requires greater investment. A well-planned monitoring schedule supports timely interventions and provides the data needed to evaluate project success and inform future plantings.

Decide how monitoring data will be recorded

Tree monitoring data can be recorded using either online forms and digital tools, such as mobile apps, or paper-based methods like printed forms and manual data entry.

Recording data digitally offers several advantages, particularly for capturing accurate location data when GPS or satellite mapping is available. Digital tools also streamline data storage, analysis and sharing. However, they require access to smartphones or tablets, which may be cost-prohibitive or impractical in some contexts.  

Paper forms are a reliable alternative to digitally recording data. After data is collected on paper forms, it can later be entered into a digital spreadsheet or database to allow for easier analysis and long-term storage.  

The method you choose should balance cost, available equipment, user familiarity and the scale of the inventory. Selecting a method that fits your team’s capacity and project scale will help ensure that monitoring is consistent, accurate and sustainable.  

Technologies and tools used for data collection and analysis may include satellite imagery, aerial imagery and light detection and ranging (LiDAR), which provide visual representations of the planting sites. Geographic information system (GIS) software can then be used to capture, store, manage and analyze the resulting data.  

For more information on using tools to collect and analyze data, review our factsheet on urban forestry technology and tools. 

Create your monitoring baseline

Collecting baseline information about your newly planted trees is a critical step in managing them over the long term. Ideally, this information should be integrated into a comprehensive inventory of your municipality’s trees (or form the start of an inventory). An inventory provides a centralized record of what was planted where and how well each tree is growing over time. This supports consistent monitoring, maintenance and planning.

At a minimum, a best practice is to record the following information for each tree:

• location (GPS coordinates or map reference)

• planting site type (e.g., street, park or private)

• species and cultivar (or genus, if more feasible)

• health status

• land use type (e.g., urban, forest, open space, industrial)

• diameter at breast height (or at one foot, depending on tree size)

• date of recording

• a unique tree identifier 

This baseline data forms the foundation for all future monitoring. Over time, you can add and update information, such as the following:

• health status observations

• structural observations

• growth

• maintenance actions (watering, pruning, staking, etc.)

• survival/mortality status

Tracking this information over time allows you to identify trends, evaluate planting success and quickly detect areas or species that may require more attention. 

Recording every individual tree may be impractical for large-scale restoration projects that involve mass plantings. In these cases, you can use sample plots to inventory and monitor select trees on your site, then extrapolate that data to the entire site. This will generate a representative picture of the planting’s performance while still collecting detailed inventory data for selected sample trees. You can also track site-level characteristics (e.g., soil quality, ground cover and canopy cover) and metrics related to the goals of the restoration project (e.g., land area restored, carbon sequestered, presence of wildlife, etc.). Although these indicators go beyond tree monitoring, they are essential for assessing the overall success and ecological impact of restoration efforts.

Quality control in tree monitoring

To maintain accurate and consistent data over time, make sure to build quality control into your monitoring plan. This includes deciding when data will be reviewed and who is responsible for verifying measurements.
A common method is to randomly select five to ten percent of trees for remeasurement by a trained supervisor or second observer. This helps identify inconsistencies and improves data reliability for both professional and volunteer observations. Any issues can be addressed through refresher training or protocol updates.
When inventories are conducted by trained tree care professionals, identifying trees to the species or cultivar level is ideal. However, when community groups are leading the inventory, it may be more practical to identify trees to the genus level to maintain accuracy.

Photographs are another valuable quality control tool. Taking clear, consistent photos of individual trees allows teams to verify observations and validate assessments remotely.

Monitor for tree health, structure, mortality and site conditions

Once baseline inventory data has been collected, regular monitoring can begin. Tree monitoring should evolve over time, reflecting a tree’s development stage, the surrounding site conditions and the goals of your project. Health, structure, mortality and environmental factors are core indicators to monitor throughout a tree’s life, but the methods used, frequency of monitoring and level of detail will depend on tree age and project type.

All maintenance activities completed should also be documented, ideally in your tree inventory. This record-keeping supports ongoing monitoring, clarifies a tree’s maintenance history and informs future asset management planning.

Monitoring newly planted trees

Tree health

Early tree health monitoring (up to three years after planting) will focus on survival and establishment. Monitoring indicators that reflect how well a tree is adapting to its new environment is key. This may include monitoring overall vigour, chlorosis, leaf or needle loss, shoot growth, and signs of disease or animal damage. These indicators can reveal issues such as water stress, nutrient deficiencies or pests, which can be addressed by more frequent watering and other maintenance activities. 

Tree structure

Monitoring structural development is also key during the establishment phase, as early intervention can prevent costly or hazardous issues later in a tree’s life. Structural indicators to look for include trunk lean, co-dominant stems, poor branch attachment, mechanical damage from stakes or animals, and root girdling. Addressing these early through pruning, staking adjustments or installing protective fencing can set trees on a path to long-term stability and health.

Tree mortality

Tracking mortality is especially important during the establishment period to evaluate project success or progress toward survivorship goals, such as achieving 80 percent survival three years after planting. Regularly recording which trees have survived provides valuable insight into planting methods, species performance and potential site challenges. When mortality is high, monitoring data can help identify the causes, such as drought, pests, vandalism or improper planting techniques. Doing so will inform both corrective maintenance actions and long-term planning.

Site conditions

In urban or high-traffic areas, environmental stressors like soil compaction, drought, vandalism and invasive vegetation can significantly affect trees. These observations can help explain poor health or high mortality and then guide targeted interventions. If the cause of stress is not obvious, it may be due to soil pollution (e.g., salt contamination) or nutrient levels. If this is suspected, it can be useful to conduct laboratory testing to determine the cause of the problem.

For restoration or afforestation projects, soil testing and monitoring for invasive vegetation is especially important as goals often include improving degraded soils, managing erosion and re-establishing native plant communities.

Monitoring established trees

After three to five years, trees are typically considered to be established. While they require less frequent care than young trees, regular monitoring—perhaps integrated into a larger municipal or site inventory—is recommended for long-term health and safety. At this stage, the focus shifts from monitoring survival to looking at growth, signs of chronic stress, structural issues and the presence of pests or disease. 

Next steps

Here are some additional resources that can help you develop a monitoring program for your tree planting projects:

This resource was created in partnership by Tree Canada and FCM’s Green Municipal Fund for the Growing Canada’s Community Canopies initiative, which is delivered by the Federation of Canadian Municipalities and funded by the Government of Canada.