New Zealand gets significant weather every year, westerlies through Wellington, cyclones tracking down the upper North Island, autumn nor'westers in Canterbury, southerly fronts in Otago. The trees that fail in storms are rarely the trees that look bad, they're the trees nobody walked around in fair weather.
Here's the walk-through we recommend doing every autumn before peak storm season, on any mature tree within fall-distance of a building, car or driveway.
1. Walk the base, look down
Look for: lifting soil on one side of the trunk, gaps between trunk and ground, recently exposed roots, mushrooms or bracket fungi at the base. Any of these need a closer look from an arborist, they're the signs of root anchorage failure.
2. Walk the base, look up
Stand at the trunk and look up the canopy. Look for: dead branches in the upper third, splits where major branches join the trunk, broken or hanging limbs that haven't fallen yet (called "hangers"), bird nests with no leaves around them, sap weep down the trunk.
3. Check forks and unions
Where the trunk splits into two or more main stems, look at the bark in the crotch. If it's pinched in tightly with bark visible all the way down (called "included bark") rather than wrapping smoothly between the two limbs, the union is structurally weak. These fail in storms more than any other single defect.
4. Look at the lean
Trees that have always leaned are usually fine, they've grown reaction wood to compensate. But if the lean is recent, or if it's combined with soil lifting on the opposite side, that's a red flag for root plate failure.
5. Look at the species
Some species are much more prone to wind damage than others. Top of the failure list on NZ properties: eucalyptus (limb-drop without warning), Leyland cypress (brittle and wind-throw prone), willow (limb-shed), poplar (whole-tree throw), large macrocarpa with one-sided canopies.
6. Look at what's underneath
A failure is only a problem if there's a target. House? Car? Driveway? Kids' play area? Power line? The closer the target, the lower your tolerance for risk should be.
What to do about it
- Crown thinning: the most useful storm-prep job we do. Selective removal of small branches throughout the canopy reduces wind sail by 15–25% without changing the tree's shape.
- Crown reduction: reducing height and spread on top-heavy trees, particularly on shallow soils.
- Deadwood removal: takes out the limbs most likely to fall and most likely to damage live structure.
- Bracing or cabling: for high-value trees with weak unions where retention matters.
- Removal: for trees where the structural problem is too significant to mitigate.
When to book the work
Late summer and early autumn (Feb–April) is the sweet spot. The tree is still in good growing condition to seal cuts before winter, and you've got the work done before the storm season really hits.