Eucalypts are not inherently dangerous trees, and the folklore about them — that they “drop limbs for no reason” — is mostly wrong. Limbs come down for reasons. Many of those reasons are visible from the ground if you know the shape of what you are looking at.
This is a guide to noticing, not a substitute for assessment. Nothing on this list tells you the probability of failure, and that is the number that actually decides what to do.
Start at the base
More whole-tree failures begin below knee height than anywhere else.
- Fungal fruiting bodies. Brackets, conks or mushrooms at the base or on buttress roots indicate active decay in the structural wood. A bracket is the reproductive body of a fungus that has already been working inside the tree for years.
- Hollow sound. A mallet or the heel of your hand along the lower stem should produce a dense, solid note. A drum-like or hollow tone over a section suggests internal decay.
- Basal cavities and old wounds. Particularly where the opening is wider than about a third of the stem circumference.
- Soil movement, lifting or cracking on one side. This is the serious one. Cracked or heaved soil on the side opposite a lean indicates the root plate is moving. It is a short-notice indicator.
- Severed or damaged roots. Recent trenching, driveway work, levelling or compaction inside the root zone. Root damage is invisible from the crown for one to three seasons, then the crown tells you.
Then the stem and unions
- Included bark at a fork. Where two stems of similar size meet in a tight V rather than a rounded U, bark can become trapped in the union instead of wood knitting across it. These unions fail, and they fail at the worst moment — under wind and water load.
- Codominant stems. Two competing leaders of similar diameter, especially above a target. Common in open-grown Eucalyptus tereticornis and E. grandis.
- Longitudinal cracks. Vertical splits in the stem, particularly new ones or ones that weep.
- Bulges, ribs or flutes. Reaction wood laid down around a weakness. The tree is telling you where it is compensating.
- Old failure points. A stem that has already lost a major limb often has decay entering at that wound.
Then the crown
- Deadwood. Some deadwood is normal. Multiple dead branches over 100 mm diameter above an occupied area is not — that is the classic falling-limb scenario.
- Epicormic growth. Dense shoots erupting directly from the trunk and major limbs is a stress response. After fire it is a survival signal; on an undisturbed tree it usually means root damage or crown decline.
- Crown dieback from the top down. Progressive death of the upper crown — “stag-heading” — commonly reflects a root or water problem, not a branch problem.
- Hanging or lodged limbs. A detached limb caught in the canopy is the original widow maker. It is not stable and it can come down in still air.
- Asymmetric or one-sided crown. Particularly where the weight sits over the target.
Species notes for South East Queensland
| Species | What to watch |
|---|---|
| Eucalyptus grandis (Flooded Gum) | Very large, fast, often retained close to houses. Basal decay and root-plate issues on wet sites. |
| E. tereticornis (Forest Red Gum) | Codominant stems with included bark; large deadwood retained in crown. |
| Corymbia citriodora (Spotted / Lemon-scented Gum) | Generally sound, but tall with high impact energy; branch shedding in heat events. |
| E. robusta (Swamp Mahogany) | Wet sites, root issues where drainage has changed. |
| Lophostemon confertus (Brush Box) | Usually well-structured; watch union defects on open-grown specimens. |
What the list cannot tell you
Whether any of it matters. A tree with three of these features over an unused corner of a paddock may be broadly acceptable. A tree with one of them over a playground may not be. Risk is a function of the defect and what is underneath and how often it is occupied — which is what a quantified assessment resolves and a visual checklist cannot.
Use this to know when to ask. Not to decide.