Gahnia Grove is a weeding project we began on the spur of the moment on 20 May 2018, while walking along the Glenfield Rd margin of Eskdale Forest. It was recorded intensively with photos and journals in the citizen science website iNaturalist.nz.
Eskdale Forest is part of one of the largest native ecological corridors in the Auckland Region, from Bayview and Glenfield, through Birkdale, up to Hillcrest.
The forest reserve was created by the acquisition of various separate lots which had been used for forestry, horticulture and agriculture. As each lot was acquired it was allowed to regrow from the remnants of the original kauri forest, till forest covered most of the final Reserve area.
This passive restoration project was supported by successive Councils with felling of the remaining pine trees, and control of some of the other invasive tree and shrub weeds.
On our roadside bush-edge walk that day we encountered the gloomiest patch of wasteland imaginable, a forest margin of dead and dying small trees hung with a canopy of weed vines, unreachable across a little gully of tangled uncontrolled kikuyu and blackberry.
Over a couple of weekends we pulled back the weed carpet, kikuyu inseparable from honeysuckle, then began to cut our way through a wall of Japanese honeysuckle 2-3 metres thick and 3-4 metres high, revealing the rotting forms of the small trees it had smothered and strangled.
Below left: June 2018 – over a few weeks the bank has been weeded to within a few metres of the forest edge, where a wall of honeysuckle has completely covered small trees and shrubs, and almost completely covered a cabbage tree/ti kouka on the right
(slide over image left or right)
Above Right: April 2023 – the honeysuckle, blackberry, kikuyu, ginger and other weeds have been eradicated from this entire area, “The Arena”, (and from adjacent areas).
Above: October 2018 – The strangled ti kouka and forest margin have been released from the honeysuckle, which had runners up to 7 metres long running into the forest behind. The thickest stems were several centimetres thick. These were sawn part way through near the base, the mass of vine and foliage pressed over the roots as mulch, and after a few months of self-rotting were able to be uprooted, never to return.
Above and below: October 2019 – Released from destructive weeds, the survivors are thriving.
Young native revegetation has progressed up the bank, with the aid of some seedlings planted on the exposed upper bank. The trees are densely surrounded by mostly wild native shrubs, grasses and creepers, with a few introduced (weed) species allowed to remain to complete dense ground cover.
Below: January 2026 – views from about the same spot, facing West to match the above images, showing the dense mostly-native groundcover under a canopy of karamu 3-4m high.
and (below) facing SW.
Beneath the young trees in the lower left of the photo below, we can see part of the “tiptoe path”, formed in 2018 of woody weed materials to avoid trampling during the early intensive weeding, and now surfaced with the spreading native creepers and grasses.
The black trunk of the Hoheria/lacebark hidden behind the young trees in 2026 (above, right of centre) is two or three times the height it was in June 2018, when it was released, along with the surrounding forest margin, from dense honeysuckle
(Below) the view in June 2018 from almost the same spot, but facing South
The edge of the kikuyu path can be seen to the left of the green leafy hoheria, with uncontrolled kikuyu and honeysuckle covering the bank to its right.
By October 2018, the mown kikuyu was being mulched as weed material became available, initially using the pulled-back kikuyu and cut honeysuckle
and by June 2020 the kikuyu was being replaced by native shrubby toatoa supported by benign weeds (mostly plantain, bristly oxtongue, wild geraniums and Verbena)
All weeds arising here are much easier to control now, due to the build up of loose ground litter and rich loose topsoil formed from the decomposing weeds since herbicide spraying was suspended in June 2018. Most light-dependent weeds are now shaded out, and the rest soon will be.
The most significant weed remaining is Creeping buttercup, which persists in both sun and shade, its suckers able to suppress wild native seedlings and sporelings.
The other weed requiring control is bindweed, which hides underground in winter, and climbs to reach the light in Spring. Bindweed can strangle and smother young trees, even uprooting them, if not controlled.
However, with diligent ongoing removal of stems as they appear, there is much less bindweed here than before our restoration started.
In fact in 2020, before a 3 month interruption of our usual monitoring and weeding in 2021, bindweed had been almost eradicated, and we planted the native bindweed species, after finding it growing wild in the raingarden in Domain Rd. However, the native bindweed proved as potentially destructive as the introduced weed, so we removed it about a year later. Now, the bindweed we are controlling could be either the native or the introduced weed species, (which, in Eskdale Reserve as much of the rest of NZ,, is itself a hybrid of the native and introduced species, (“Calystegia silvatica x sepium” is probably the simplest of the names currently applied to this hybrid).
Surrounding Gahnia Grove is a large area of mown kikuyu. We control this kikuyu along the mown margin by the “pull-back” method, which prevents the new regrowth from re-invading the restoration site.
Above: the same hoheria (centre), bank top, and forest margin, from the area of kikuyu still being mown in November 2018
Below: April 2023 – now with a cordon along the current restoration site boundary, now extended to include both harakeke and the ground between them, making weed control easier
The foreground is dominated by the young native trees, shrubs, grasses and creepers that have, over a period of nearly 5 years handweeding, replaced a large expanse of mown kikuyu.
Below: January 2026
In summary, native trees, herbs, shrubs, grasses and small creepers, mostly wild with the addition of a few dozen ecosourced seedlings planted on the upper bank, now densely cover the previously weed filled bank, as well as the area that was mown kikuyu until 2018, and on the upper edge, until 2020.
At time of writing in April 2026, we are preparing a Training Course teaching the principles, methodology and techniques used and further developed throughout the Gahnia Grove trial. We hope to be able to include videos showing the changes in Gahnia Grove site over its 8 year history from 2018 to 2026.
Subscribe for updates as Course modules are made available for public participation, beginning with the Kikuyu Module – controlling or eradicating kikuyu without chemicals, digging or cutting.
