After a big storm passes, the obvious damage gets dealt with first: trees across driveways, limbs through fences, branches on cars. The less obvious danger is the tree that is still standing. It looks mostly intact, the wind has dropped, and everyone relaxes. Yet storm-damaged trees often fail days or weeks later, sometimes on a calm afternoon, when cracked wood or loosened roots finally give way.
Knowing what to look for, and what to leave alone, helps prevent the second round of damage that so often follows a major weather event.
First, stay safe
Before inspecting anything, keep people away from damaged trees until you have looked from a distance. Never approach a tree that is touching or tangled with power lines. Treat every fallen line as live and report it to the lines company. Children love climbing on downed trees, and pets will investigate, so keep both well clear.
Look from at least the height of the tree away. Many hazards are easier to spot from a distance than up close anyway.
Warning signs in the canopy
- Hangers: broken branches caught in the crown, sometimes called widowmakers. They can drop without warning.
- Split unions: cracks where two stems or a large limb join the trunk, often visible as a fresh, pale line.
- Twisted or partly torn limbs: branches hanging at an odd angle, attached by a strip of bark and wood.
- Large areas of lost canopy: a tree that has lost a third or more of its crown may be unbalanced and under stress.
Use binoculars if you have them. Fresh wounds stand out clearly against older bark.
Warning signs in the trunk and roots
Root and trunk damage is where storm-damaged trees are most deceptive.
- A new lean: compare with photos or memory. A tree that has shifted even a few degrees since the storm may have broken roots.
- Soil heave: raised, cracked or mounded soil on the side away from the lean shows the root plate has lifted.
- Gaps at the base: a visible gap between trunk and soil on the windward side, or fresh soil cracks circling the tree.
- Vertical cracks in the trunk: long splits running up the stem, sometimes opening and closing as the tree sways.
- Exposed or snapped roots: particularly on trees growing beside banks, streams or recent excavations.
Soil saturated by days of rain makes root failures more likely. Trees on shallow soils, on slopes or in recently disturbed ground deserve extra caution.
Particular risks with certain trees
Palms can lose their crown or snap at the trunk with little warning. Old pines and macrocarpa often fail at the root plate. Eucalypts can shed large limbs in calm weather after a storm. Trees with existing decay are always more likely to fail, so earlier fungal brackets or cavities matter. For palms specifically, this article on deciding when a palm needs to be removed goes into more detail.
Buildings, insurance and next steps
If a tree or limb has struck a house, take photos before anything is moved and contact your insurer early. Insurers often want to see the damage and may arrange emergency work. Do not climb onto a roof under a damaged tree.
Structural damage to a building raises its own questions about safety and repairs. The Ministry of Business, Innovation and Employment’s building site at building.govt.nz has general guidance on building work and what may need consent, which is worth reading before arranging repairs.
For the tree itself, have a qualified arborist assess anything with the warning signs above. Most councils allow urgent work on protected trees that pose an immediate danger, usually with notification afterwards, but check the specific rules if a tree is scheduled.
What not to do
Do not try to winch a leaning tree upright yourself, and do not cut into a tree that is under tension. Storm-damaged wood is often loaded in unpredictable ways, so a single cut can release a trunk or limb with enormous force. Chainsaw injuries rise sharply after storms for exactly this reason. Leave tensioned or hung-up material to trained operators.
Frequently asked questions
How long after a storm can a damaged tree still fall? Failures can happen days, weeks or even months later, especially if more wind or heavy rain follows.
Can a tree with a split trunk be saved? Sometimes, using cabling or bracing, but it depends on the size of the split, the species and what lies underneath.
Should I remove all trees near my house after a bad storm? Not necessarily. Healthy, well-structured trees often come through storms well. Base decisions on an assessment rather than fear.