The southerly that crossed Christchurch in July 2024 was forecast three days out: gusts to 90 km/h from the south-west, sleet on the Port Hills above 300 metres. I spent the afternoon before it walking a Cashmere section on Hackthorne Road where a 24-metre Eucalyptus globulus stood 11 metres from the back bedroom. Since the 1990s I have run the same checklist before every big southerly, and every council or insurer report I write is a longer version of it. The tree lost a 200-millimetre limb that night. It landed on lawn, where the checklist said it would.
Start with what the tree would hit
A tree is not a hazard on its own. It becomes one when there is something under it, so the first line on my sheet is the target: bedrooms, the neighbour’s roof, the driveway, the footpath, a power line. I sketch the crown footprint on a site plan and mark which limbs reach which target. On Hackthorne Road a limb failure would hit garden; a whole-tree failure would hit the bedroom. Those are two different risks with two different responses, and lumping them together is how people end up removing trees that only needed pruning.
Roots and the ground they sit in
I walk the full circle of the root plate before I look up. Cashmere sits on Port Hills loess, firm when dry and poor at holding roots when saturated. What I look for is soil cracking or heave on the side opposite any lean, mounding at the base, fungal brackets at ground level, and any trenching within the last five years inside a radius of about five times the trunk diameter. A trench 3 metres from a 900-millimetre trunk removes a meaningful share of the anchoring roots on that side, and the tree will not tell you about it until the wind does.
Fungi get their own line. Armillaria shows as honey-coloured toadstools in autumn and white fans under the bark at the base; Ganoderma as hard shelf brackets. Either one on a mature eucalypt or pine changes my recommendation from prune to remove.
Trunk, forks and the history written in the bark
The trunk gets sounded with a mallet for hollow notes and inspected for cracks, cavities, bulges and cankers. Forks are checked for included bark, the seam where two stems have grown together with bark trapped between them instead of a proper union. A fork with a ridge of bark standing up along the join is sound; one with a crease sinking into the join is not, and on a eucalypt at height it is the single most common failure I record.
Then the history. Old pruning wounds tell me who has been at the tree and how. Big flat cuts on the ends of limbs with a broom of regrowth above them mean the tree was topped at some point, and every one of those shoots is anchored in decaying wood. I covered what that does to a tree in the piece on crown reduction versus topping on a Hamilton East oak; the short version is that topped trees go on my list twice.
The crown, and the species you are standing under
Deadwood over 50 millimetres in diameter, hanging broken limbs, limbs extending well beyond the crown with a heavy tip load, and any sign the crown has thinned since the last visit. Species matter. Eucalypts drop large live limbs in calm weather, and their wood is dense enough that a 200-millimetre branch weighs as much as a person. Radiata pine holds deadwood for years then sheds it all at once. Macrocarpa in old shelter belts has long horizontal limbs that fail at the trunk. Silver birch and poplar are simply brittle.
The response is graded. Deadwooding a 24-metre eucalypt runs NZ$1,200 to NZ$2,500. A 15 to 20 percent crown reduction is NZ$2,000 to NZ$4,500. Removal in a Cashmere back garden with no truck access is NZ$5,000 to NZ$9,000 and may need consent if the tree is scheduled. A site assessment is NZ$300 to NZ$600; a written report for an insurer or council, NZ$800 to NZ$2,000. Sometimes the recommendation is to move the car and shut the back bedroom for the night, and that costs nothing.
If any of this is going to be done by the owner rather than a contractor, the limit is firm: nothing with a chainsaw above shoulder height and nothing from a ladder. The WorkSafe guidance on tree work exists because those two situations fill the accident statistics, and a southerly is not the week to add to them.
Frequently asked questions
What are the warning signs a tree will fail in a storm? Cracked or heaved soil around the base, fungal brackets at ground level, a fork with bark folded into the join rather than ridged over it, deadwood over 50 millimetres, old topping cuts with dense regrowth, and a lean that has appeared or increased recently. Any two together justify an assessment before winter.
Should a leaning tree be removed before winter? Not on lean alone. A lean the tree has grown with for decades, with the trunk curving back to vertical and no soil disturbance at the base, is usually stable. A lean that is new, straight, and paired with cracked or mounded soil on the opposite side is a removal candidate.
How much does a hazard tree assessment cost in Christchurch? A site visit and verbal assessment runs NZ$300 to NZ$600. A written report suitable for a council consent application or an insurer is NZ$800 to NZ$2,000 depending on the number of trees and whether decay testing is required.