Sydney Tree Company’s certified arborists perform tree health inspections across Sydney as a regular part of their work. Understanding what the inspection process involves helps property owners know what to expect, what information is useful to provide, and how to interpret the findings and recommendations.
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Why Tree Health Assessment Matters
Trees are living structures that age, experience stress, contract disease, and respond to the physical environment in ways that are not always visible to the untrained eye. A healthy-looking crown can conceal significant internal decay. A modest lean in a tree can be stable or dangerous depending on the root system and the soil conditions.
Arborists use a structured inspection process to assess trees against a range of indicators because any single indicator, taken in isolation, can be misleading. The value of the professional inspection is the integration of multiple observations into an assessment of the tree’s overall condition, structural integrity, and risk to people and property.
Level 1 Inspection: Preliminary Visual Assessment
The starting point for any tree health assessment is a ground-level visual observation of the tree from multiple angles. This is sometimes called a Level 1 inspection or a preliminary visual assessment, and it forms the basis for all subsequent work.
During the Level 1 inspection, the arborist is observing:
- Overall crown condition: is the canopy full and even, or are there areas of thinning, dieback, or missing foliage? Uneven crown development, particularly on one side, can indicate root zone problems, disease, or structural stress
- Bark condition and colour: is the bark intact and appropriate for the species, or are there cracks, loose sections, areas of exfoliation that go beyond the normal for the species, or bleeding or discolouration? Dead bark sections (indicated by bark that peels away from the wood beneath) are a reliable indicator of deadwood in that area
- Structural form: does the tree have a sound, single leader structure appropriate for the species, or are there codominant stems with included bark (where two stems grow together with bark compressed between them, creating a structurally weak union)? Codominant stems with included bark are one of the most common causes of major structural failure in urban trees
- Lean and direction: is there a lean, and if so, is it accompanied by soil heaving at the base or cracking soil on the opposite side? A lean without these signs may be stable; a lean with disrupted soil is a different matter
- Previous pruning and wound response: how has the tree responded to past pruning? Good wound response (callus formation closing over cut surfaces) indicates vitality; wounds that have not closed after years may indicate declining health or poor pruning technique that has introduced decay
Level 2 Inspection: Detailed Assessment
Where the Level 1 inspection identifies concerns or where the inspection is for a specific risk management or development application purpose, a more detailed Level 2 assessment is performed. This typically involves a closer examination of specific areas of concern identified in the preliminary assessment.
The Level 2 assessment may include:
- Crown and upper stem inspection: this involves the arborist getting physically closer to the upper parts of the tree, either using climbing techniques or an elevated work platform, to inspect deadwood, branch attachments, and canopy condition that cannot be adequately assessed from the ground
- Root zone inspection: examining the soil around the base of the tree (the critical root zone) for signs of root disturbance, compaction, soil contamination, fungal growth at root collar level, and physical barriers that may be restricting root development
- Fungal fruiting body identification: the presence of fungal fruiting bodies (conks, brackets, or shelf fungi) on the trunk, root collar, or at the base of the tree is one of the most reliable external indicators of internal decay. The location, size, and species of the fungi provides the arborist with information about the likely extent and location of internal decay
- Canopy density and leaf condition: close inspection of leaves for signs of disease, pest infestation, chlorosis (yellowing indicating nutrient deficiency), and physical damage
| 🌳 The base of the tree is as important as the top: Many property owners focus on the crown of a tree when assessing its condition, but the base of the trunk (the root collar) and the root zone are frequently where the most significant structural and health problems originate. An arborist will spend as much time looking at the lower trunk and soil around the tree as they do at the canopy. |
Advanced Diagnostic Assessment
For trees of high value, trees in locations where failure would be particularly dangerous, or where external indicators suggest significant internal conditions, advanced diagnostic tools can provide additional information about internal wood condition:
- Sonic tomography: this technique uses sound waves transmitted through the wood to map internal density variations. Areas of internal decay produce different acoustic responses to sound wood, allowing the arborist to map the approximate location and extent of internal hollows or decay without invasive sampling
- Resistograph: a fine, needle-like probe is driven into the wood at a measured resistance. The resistance profile as the needle passes through the wood reveals variations in density that indicate the presence of decay, hollow sections, or cracks
- Soil assessment: soil compaction, drainage conditions, and chemistry can significantly affect tree health. In specific cases, soil testing and assessment of the root environment provides important additional context for the health assessment
These tools are not used in every inspection: they are applied where specific concerns identified in the visual assessment warrant further investigation, and where the cost of the additional assessment is proportionate to the value of the tree and the importance of accurate information.
What the Arborist Is Looking for: A Summary
| Inspection area | Key indicators of concern |
|---|---|
| Crown and canopy | Dieback, uneven foliage, premature leaf drop, reduced vigour |
| Trunk and bark | Cracks, cavities, fungal fruiting bodies, bleeding, loose bark |
| Branch attachments | Included bark, codominant stems, cracks at junctions |
| Root collar (tree base) | Fungal growth, buttress root damage, soil heaving, cavities |
| Root zone | Compaction, construction damage, surface roots with damage, soil conditions |
| Overall structure | Lean, asymmetry, storm damage history, proximity to hazard targets |
The outcome of the inspection is a professional assessment of the tree’s health, structural condition, and risk rating, along with recommendations for management. These may range from a clean bill of health to specific pruning works, to a recommendation for removal.
When to Request a Tree Health Assessment
Regular professional assessment is worthwhile for any significant tree on or adjacent to your property. Specific triggers that make an urgent assessment important:
- After a major storm event, particularly where branches have been lost or significant debris has fallen from the tree
- Where you notice any of the external warning signs described in this article: fungal growth, cracking bark, crown dieback, or unexplained lean
- Where a tree has been subject to construction or landscaping activity that may have damaged the root zone
- Before purchasing a property with significant trees, as part of your due diligence
- Where a neighbouring property owner or council has raised concerns about a tree’s condition
- Where you are applying for development consent that involves trees, as an arborist report is often required as part of the development application
Sydney Tree Company’s certified arborists provide tree health assessments across all Sydney areas for residential, commercial, and local government clients.
Get a Professional Tree Assessment in SydneySydney Tree Company. Certified arborists. 20+ years. Sydney-wide service. Call 0431 732 265. |
Frequently Asked Questions
How often should a mature tree be professionally assessed?
For healthy trees in stable conditions, a professional assessment every three to five years is a reasonable maintenance interval. Trees in higher-risk locations (near structures, over pedestrian areas, adjacent to power lines), trees that have shown any signs of decline or structural concern, and trees subject to development or construction activity nearby should be assessed more frequently. Contact Sydney Tree Company to discuss an appropriate inspection schedule for your specific trees.
Can I do my own tree health assessment?
Property owners can and should regularly observe the trees on their property for obvious external signs of concern: changes in crown density, fungal growth at the base, loose bark, or significant lean following storms. These observations are valuable and should prompt a professional assessment if anything unusual is noticed. However, the detailed structural and health assessment described in this article requires professional training, equipment, and the species knowledge that a certified arborist brings to the assessment.
Do I need an arborist report to get council permission for tree removal?
In many Sydney councils, a report from a qualified arborist is required as part of a development application or tree removal application, particularly for trees that are protected under the local council’s tree preservation order or Local Environmental Plan. Sydney Tree Company can provide arborist reports as part of the removal application process. See the preservation orders page for links to your local council’s requirements.