Few garden jobs carry as much quiet risk as trimming near an overhead line. New Zealand has specific rules about how close trees can grow to electricity lines, and they are less mysterious than they first appear once you strip away the formal wording.
This is a plain-language overview for homeowners. It is not a substitute for reading the official material or talking to the lines company that owns the wires on your street.
Two zones you need to know about
The national tree regulations for power lines work around two invisible boundaries that surround each conductor.
- The notice zone is the outer band. When a tree grows into it, the lines company can issue a notice to the tree owner saying the tree is getting close and will need attention.
- The growth limit zone is the inner band, closer to the wire. Trees must not encroach into it. Once a tree is inside this zone, the owner may be required to have it cut back, and work inside it must be done by approved, trained people.
The exact distances depend on the voltage of the line and the span length, so a low-voltage service line running to a house has a much smaller zone than a high-voltage line along a rural road. Distances apply in all directions, including to branches swaying in wind.
Who pays and who does the work
In broad terms, the first cut after a tree owner receives a notice is often handled by the lines company at its own cost, as long as the owner responds properly. After that, keeping the tree clear becomes the owner’s responsibility. If you decide you no longer want the tree, there is usually an option to declare no interest in it, which shifts future trimming to the lines company but means you cannot object to how it is cut.
For service lines that run from the street pole to your house, the picture is different. Those lines are frequently the property owner’s responsibility, so trees near them are entirely your concern, both for cost and safety. Expect to pay anywhere from a couple of hundred dollars for a small trim to well over a thousand NZD for a large tree that needs a line-qualified arborist and possibly a temporary disconnection.
What you can safely do yourself
The honest answer is very little once branches get anywhere near a line. Electricity can arc across a gap, and green wood conducts well enough to be lethal. Sensible limits for a homeowner include:
- Pruning young trees well away from lines so they never reach the zones at all.
- Removing low branches that are clearly metres away from any wire, using hand tools and keeping your whole body and tools well clear.
- Calling the lines company or a line-qualified arborist for anything else, especially branches resting on or above a wire.
Never climb a tree that touches a line, and after a storm treat any downed wire as live.
Planning planting around lines
The cheapest clearance work is the work you never need. When planting under or near lines, pick species whose mature height stays well below the wire. In the Bay of Plenty, options such as hebes, corokia, small coprosmas, and dwarf citrus fit comfortably under most residential lines. Taller natives like tōtara, kahikatea or pūriri belong in an open part of the section where they can reach their full size without pruning.
The Bay of Plenty Regional Council’s regional environment and land information is a useful starting point when choosing species suited to local soils and avoiding plants listed as pests. Big trees also bring other maintenance considerations; the article on leaf litter, moss and roof care under large trees covers what happens when canopies spread over a house.
Frequently asked questions
How do I find out who owns the line near my tree? Check your power bill for the network company name, or look for an identification tag on the nearest pole. The local lines company can tell you whether a line is theirs or a private service line.
Can a lines company cut my tree without asking? In an emergency, such as a branch on a live wire during a storm, they can act immediately. For routine trimming, notices are normally issued first, giving the owner time to respond.
Will a tree trimmed back hard from a line recover? Many species regrow vigorously, sometimes too vigorously, sending up fast shoots straight back toward the wire. Regular, lighter trimming or replacing the tree with a lower-growing species is often a better long-term plan.