You don't need to be a qualified arborist to spot the signs of a tree that's becoming a safety problem. You just need to know what to look for. Here are seven things to check on any tree within fall-distance of something you care about.
1. Mushrooms or bracket fungi at the base
Fungal fruiting bodies on the trunk or root flare are usually the symptom of internal decay. The tree might still be sound, or might be 70% rotten on the inside, either way, it warrants a closer look.
2. Cracks in the trunk or major limbs
Vertical splits, especially long ones or ones that have grown over time, often indicate internal failure starting to express. Cracks where forks join are particularly serious.
3. Dead branches in the upper canopy
Some deadwood is normal. A large proportion of dead branches in the top third of the canopy isn't, it usually means the tree is losing its ability to push water and nutrients to the top.
4. Lifting soil or exposed roots on one side
Walk around the base. Cracks in the soil, mounding, or visibly lifting roots on the opposite side to a lean mean the root plate is starting to fail. This is the highest-priority warning sign, these trees can come down in the next strong wind.
5. Recent lean
A tree that's always leaned is usually fine. A tree that's newly leaning, or where the lean has visibly increased over months, is not. Take photos with reference points so you can track it.
6. Hangers in the canopy
A "hanger" is a broken branch that hasn't fallen, it's caught on lower branches. These come down without warning when wind shifts them, when they dry out and become brittle, or when the supporting branches let go. They need to be brought down deliberately.
7. Hollow sounds when you knock
Tap the trunk with a hammer or rubber mallet at various points and listen. Drum-like, hollow sounds suggest internal cavities. Solid, dull thuds suggest sound wood. The hollow areas don't necessarily mean the tree must come down, it depends on wall thickness, but they tell you where to look more closely.
What to do if you spot any of these
One sign by itself isn't necessarily an emergency. Multiple signs on the same tree, or any single sign on a tree over a high-value target, warrants an arborist's assessment. A tree health assessment is a couple of hundred dollars and a couple of weeks of waiting, much cheaper than the alternative.
What you shouldn't worry about
Common things that look concerning but usually aren't:
- Bark peeling, many species shed bark normally (eucalyptus, plane, paperbark).
- Small woodpecker-style holes, usually borer activity, not necessarily structural.
- Lichen and moss growing on the trunk, purely cosmetic.
- A few dead branches in the lower canopy, normal canopy thinning.
- Leaf drop, even evergreens shed leaves; some species (e.g. magnolia) drop heavily in summer.