My sister bought a 1950s brick house in Hamilton East in 2019, on a street off Grey Street where the section backs onto the river terrace. The selling point was a mature English oak, maybe 18 metres, at the back. The catch was that a previous owner had topped it in about 2014: every main limb cut flat at roughly 8 metres, and the tree had responded the only way an oak knows how, throwing up a broom of thin, fast shoots from each stub. By the time she moved in those shoots were 4 to 5 metres long, and the first serious spring blow through the Waikato dropped two of them across the shared driveway.
Her oak was the first time I saw reduction and topping side by side in one tree; the two still get quoted as if they are the same job.
What topping does to an oak
Topping means cutting through a limb at an arbitrary height, leaving a stub with no branch to take over. A 200 mm flat cut with no growth point is beyond what any tree seals. Decay runs down the stub while the tree pushes out epicormic shoots from dormant buds near the wound.
Those shoots are the problem. They attach to the outer wood of a stub rotting from the inside, not to the structural core of the tree. They grow 1 to 1.5 metres a year on a well-watered Waikato river terrace, and within a decade you have a heavier, taller crown sitting on weaker attachments than what was removed. The two limbs on my sister’s driveway were about 120 mm at the base and had been holding on to little more than bark and callus.
What a proper reduction looks like
A crown reduction shortens the tree, but every cut is made back to a lateral at least a third the diameter of the piece removed. The lateral takes over as the new leader, sap flow continues past the wound, and the tree does not need to panic-sprout. Most arborists in New Zealand work to no more than 20 to 25 percent of the live crown in one season, and less on an oak over 60 years old. You end up with a tree 2 to 3 metres shorter and lighter on the ends of the limbs, but still recognisably an oak.
It costs more because every cut is chosen and climbed to. For an 18-metre oak in Hamilton East with good rear access I saw quotes between NZ$1,800 and NZ$3,200 for a reduction, versus NZ$900 to NZ$1,400 for what one operator openly called a “top and tidy”. The cheap job is the one that costs you every five years for the rest of the tree’s shortened life.
Repairing a tree that has already been topped
You cannot undo topping, but you can manage it. At my sister’s place the arborist did restoration pruning over three visits, two years apart. First she thinned each stub to two or three of the best-attached shoots and shortened those, so the wind had less to grab. Next she chose one shoot per stub as the new leader and removed the competitors. By the third visit the survivors had laid down proper wood over the old cut face and the crown had a shape again.
Total cost across three visits was about NZ$3,600, more than one good reduction would have cost the previous owner. Two stubs were too rotten to save and were cut back to the trunk collar. She was also told that the tree would never be as safe as an unmolested one and would need inspection every two to three years, which for a tree over a driveway and a neighbour’s carport is worth knowing before you buy.
Why the Waikato makes it worse
Hamilton East’s river terrace soils are moist and trees planted there in the 1940s and 1950s grow fast. Good for a healthy tree, bad for a topped one: the regrowth is more vigorous, the stubs stay wetter, and decay fungi have an easy time. A topped oak in dry Canterbury shingle might limp along for decades; the same tree beside the Waikato puts on weight it cannot carry in half that time.
Once a tree has been cut badly, liability for what falls off it is yours. If it is too big for the space, the honest alternatives are a staged reduction, or removal and replanting with something that fits. The person doing the cutting should be able to say which lateral each cut goes back to; if the answer is a height rather than a branch, it is topping. The work at my sister’s place was done by a Hamilton tree contractor who talked through every stub before climbing, and that conversation is most of what you are paying for.
Frequently asked questions
How much can you take off an oak in one pruning? No more than 20 to 25 percent of the live crown in a season, and closer to 15 percent on an oak over 60 years old. Each cut should go back to a lateral at least a third the diameter of the limb removed.
Can a topped tree be fixed? Partly. Restoration pruning over two or three visits several years apart can rebuild a crown from the strongest regrowth, but the decayed stubs remain and the tree needs inspecting every two to three years afterwards.
What does a crown reduction cost in New Zealand? For a mature 15 to 20 metre oak with reasonable access, roughly NZ$1,800 to NZ$3,500 including chipping and removal of the material. Difficult access, powerlines or a tree over a neighbour’s roof push it higher.