Notes from Gahnia Grove

From time to time we feel moved to describe what we are seeing in our single-handed restoration project “Gahnia Grove“, covering about half a hectare of regenerating wild kauri forest along and below the Glenfield Rd margin of Eskdale Forest.

The site has three major sections – Tanekaha Ridge, Rimu Ridge, and Gahnia Grove-the-original-2018-roadside-site, in June 2018 almost nothing but vine, shrub and tree weeds with uncontrolled kikuyu tangled in honeysuckle and blackberry,

Honeysuckle smothering native forest edge

so that area was the most urgent, and made the most difference to the survival of the forest hidden behind it – see below:

At random, then, these notes from a visit last week to “Flame Tree Bank”, visible from the roadside just uphill from the strawberry stand:

Plant species diversity beginning to increase on Flame Tree Bank

Flame Tree Bank is part of the initial 2018 Gahnia Grove restoration project. It comprises the slope around the big stand of Flame, or “Coral”, trees, from the edge of the forest canopy, uphill to the recreational mown kikuyu area bordering Glenfield Rd, nearly opposite the petrol station.

In 2018 Flame Tree Bank was completely dominated by environmental weeds. The entire tangled mess, on a steep slope above regen kauri forest margin, was (and remains) overhung by invasive Flame trees. One or two trees planted in 1999 has spread through suckering and falling branches, becoming over 30 trees, most of them now occupying space in the canopy of regenerating kauri forest.

After a request to Council for intervention when we initiated our restoration of a section of forest margin we called Gahnia Grove, these trees were expected to be controlled by arborism.

Above: Flame Tree Bank in May 2018, with Elephant’s Ear, Arum lily, Cape Honey Flower, honeysuckle and Tradescantia, and kikuyu in the foreground

Below: Jan 2019: after honeysuckle was controlled by uprooting it wherever it was easy, and rolling it up, invasive bindweed took over.

The planned arborism would have destroyed or smothered much of any regen present by that time, so we did not attempt to maintain much weed control here till 2020, when it became apparent that there would be no Flame Tree control by Council.

( On the positive side, this meant the site was not subjected to the injection of poison prescribed to accompany the arborism. And over the years since 2018, necessity being the mother of invention, we have discovered we can manually control all but the largest trees, through partial breaking of branches and ringbarking of small trunks and lower branches, both of which procedures appear to have suppressed or slowed growth in the large trees of the smaller stands, while eliminating the small trees in the forest itself).

So in 2018-19 on Flame Tree Bank we controlled only honeysuckle, bindweed, ginger, Alocasia, Arum, moth plant, extensions of Flame Tree invasion, and kikuyu, allowing the more benign weeds including Tradescantia to maintain ground cover and suppress spread of environmental weeds.

Above: The second image shows Flame Tree Bank in October 2021, after control of vine and shrub weeds, with only a few wild native plants (shrubby toatoa and karamu) emerging so far among the ground-covering weeds .
(The top half of the cabbage tree on the right was knocked off by a falling Flame Tree in 2020, so it is now half the size, and has grown a new head)

During hundreds of explorations and interventions, only 12 wild native plant species were observed on this bank from 2018-2023. In addition to the wild regen, only a dozen or so 10cm H nikau seedlings were planted.

The new wild native species seen were very young seedlings released from Tradescantia in 2019

Karamu seedlings in thinned Tradescantia
Ti kouka seedlings released from Tradescantia

and later dying (due to natural attrition or drought). These seedlings were ti kouka/cabbage tree, karamu, and a few kahikatea.

The forest canopy edge down the bank had been released from Tradescantia in late 2018, and the same species of seedlings were found beneath Tradescantia regrowth in 2019:

Karamu seedling and moss in thin Tradescantia regrowth on vertical bank

This week, under the shelter of the rapidly developing regen spreading from the boundary of Flame Tree Bank top with the adjacent Cape Honey Flower (CHF) Bank top, we found:

  • a single mapou seedling
  • a single Pteris tremula sporeling
  • 2 Hebe (Veronica stricta) seedlings
Hebe seedling

and several Carex lambertiana – with more karamu seedlings, which have become common on Flame Tree Bank since 2022.

Juvenile Carex lambertiana, released Jan 2024 from Tradescantia regrowth and creeping buttercup

These 4 modest finds are all well-situated among 2-3 year-old native regen on likely to be overtaken by weed, drought or flood, not extraordinary or even of note in other situations, are very significant here.

A very weedy site gives enormous rewards, through the contrast of ugliness, waste and destruction with the harmony seen in emerging native plant communities, and the lush growth in sheltered soil enriched with the composting weed material.

We hope to find time to present some other views of Gahnia Grove before, during and after the ongoing restoration.

Kawakawa fruit are beginning to ripen

Following the development of the kawakawa fruit observed in earlier posts, I noticed a few ripe fruit on the tree outside this dining room window.

ripening and unripe kawakawa seen through open dining room window

In summer kereru clamber in the taller branches of the tree, alone, in pairs, and one year with a chick, all within a metre of this window.

Fortunately for the kereru, who are far too trusting for their own good, a dog keeps the garden cat-free, and the dog can’t reach this part of the garden.

A low branch outside the window has ripening and unripe fruit overhanging purei (Carex lambertiana)

Above: a fully ripe kawakawa fruit, found half-eaten on the ground, discloses the many seeds within the orange flesh of a single fruit

The wood of the kawakawa is soft, easily pruned to keep this paved path clear.

Wild native sedges and grasses and moss are allowed to cover the earth under the tree, and the smaller plants are allowed to spread to fill the gaps between paving tiles, keeping out most of the dandelions, creeping buttercup and other weeds.

The native kawakawa looper makes holes in the kawakawa leaves.

These holes are said to correspond to the leaves with the strongest medicinal value, perhaps because of substances produced in those leaves in response to the caterpillars eating the leaves.

Another explanation is that the caterpillars know which leaves are the best to eat.

Either way, this 2 square metres of clay is cool and refreshing to look out on through hot summers, hosts a lot of wildlife, lets morning light play on the windows all year round, and, with fallen leaves and twigs mulching the ground naturally, requires almost no attention to stay beautiful and weed-free.

Michelle’s Bank-top Bush – Pigeonwood seedlings among the weeds

Our client Michelle has a large front garden on a slope above a quiet road. Around the edges of this garden there are several large exotic trees, and numerous smaller native trees.

Michelle in her garden – transformation begun

When we started working on this garden transformation, the fences on all three sides were overhung by ivy, which had climbed the fences and the smaller native trees on the other side of the fences, and about 10 metres up a large Norfolk pine. There was also some honeysuckle growing through and under the fence, with some remaining beyond our reach on the steeply sloping roadside berm.

Michelle loves walking in the local bush, and dreamed of enjoying some of that ambience in her own large garden. Once she learned it was possible, she became keen to create a shady little bush-walk by converting the lawn and weedy borders of an unused part of her own large garden to a mostly-wild native plant community, solely by weeding, protecting the weeded ground from trampling and desiccation, and nurturing the wild native seedlings that would arise.

lawn behind woodshed, with juvenile wild karamu in foreground

We set about cutting and uprooting as much as possible of the ivy,

oxalis and grass weeds uprooted and/or suppressed with pulled weeds and cut ivy from the fenceline

and cut, uprooted or suppressed the major weeds around the edges.

Weeds turning into rich soil, with a pile of cut ivy foreground left, drying until it can be spread as mulch
A wild mapou juvenile against the fence, mapou seedlings in the foregroundh, and (lower left) a remnant of a large clump of Agapanthus being successively suppressed then uprooted

Hundreds of tree privet seedlings in the borders were easily uprooted while the ground was wet during winter, and larger ones, along with other tree weeds, were suppressed with a versatile pruning technique that leads to the weed-tree’s death over a year or two.

foreground – a newly uprooted Agapanthus (left) and 4 or 5 wild mapou seedlings (centre foreground -yellowish leaves and reddish stems)

at the base of a large Norfolk pine and a young totara, (left) a wild Macadamia seedling being suppressed by pruning, and helping to suppress other weeds, including ivy and Agapanthus which were later uprooted easily

Many native tree seedlings had already arisen wild among the weeds, and were released over a month or so to provide the basis of the new bush garden. As is usually the case, karamu was the commonest wild native,

one of the many wild karamu seedlings found hidden by the invasive and very dominant Blue corn-lily (Aristea ecklonii – suppressed, top left and foreground – later easily uprooted)

but as the hand weeding proceeded over the next few months we also discovered many wild mapou and houpara seedlings, and several rewarewa.

Today we were thrilled to find two wild seedlings of pigeonwood (porokaiwhiri, Hedycarea arborea).

We have seldom seen pigeonwood outside of forest reserves. These seedlings have appeared in Michelle’s garden under a large Norfolk pine and young totara, with many species of trees and shrubs nearby, including those that attract birds that feed on berries.

There are no pigeonwood in this or neighbouring gardens, so a bird has fed on pigeonwood somewhere else, then come to Michelle’s garden to eat; perhaps the berries of native karamu, mapou or houpara (five-finger), or the exotic (and invasive) cotoneaster, ginger or Mexican fan or bangalow palms.

These two pigeonwood seedlings germinated among ground-covering weeds including Aristea ecklonii (Blue Corn lily), oxalis, ground-runners of ivy, kikuyu and Veldt grass. Fortunately we had suppressed most of these weeds a few months ago, leaving all the loose weed material as a thick mulch to rot those that did not uproot easily.

left of centre – the two tallest wild karamu seedlings under the totara and Norfolk pine, with cut ivy piled against the fence

Today we were able to uproot most of the remainder of the weeds, and used the newly pulled weeds to mulch a little more of the lawn’s weedy edge. The soil after weeding is a lovely loose loam, full of composted weeds and lawn clippings, making a seed-bed that will support many more seedlings.

However, the soil surface is drying out fast now the prolonged rainy period is over, so we placed handfuls of weed-material around each of the native seedlings, and shaded small seedlings and bare soil (potential seedbeds) with the woody ivy branches which had been cut and piled over the last few months.

The leaves still hanging from the cut ivy branches provide a scattered partial shade, and the woody branches will keep their shape well into summer, providing a “tent-frame” over which other plant materials can be hung once the ivy leaves fall from their branches.

a karamu seedling found wild elsewhere in the garden has been transplanted here in the rich, friable soil formed from decomposing grass clippings and weeds, and now partially shaded by some cut ivy

Not all seedlings survive, especially outside of the shade and protection of a compatible plant community. We hope to update you on the fate of these two pigeonwood seedlings in a future post.

Wikipedia has this to say about pigeonwood:

Hedycarya arborea, commonly known as pigeonwoodporokaiwhiri, and poporokaiwhiri[1] is an endemic tree of New Zealand. Found on both the North and South islands of the country, the tree grows to a height of 15 metres. The leaves are oval shaped with shallow serrations. Ripe fruits turn red and the plant received its common name back when it was assumed that the New Zealand wood pigeon particularly favoured them, based on observations of the birds eating the fruit. It has since been discovered that the New Zealand wood pigeon does not prefer these berries, and tends to eat them as a ‘famine food’ when better fare is not available”.

Time to act before the Spring rush

Just a reminder that Spring is underway as far as the plants are concerned, and weed vines and shrubs are putting out new shoots, sneaking around garden shrubs, drinking up the lovely water and increasing sun, and finding new ground to conquer.

Big weed invasions yield the most material for paths, mulch and compost, and the first big weeding produces a massive amount of plant material to be either sent to landfill or used to benefit the soil and plants by decomposition onsite.

Once the ground dries, sun comes out, and rain is infrequent, decomposition by rotting slows down or stops altogether.

We don’t encourage storing big piles of dry woody or papery material during the fire season, so if you have a lot of woody weeds to be dealt to….that is, vines, shrubs or trees…work needs to start very soon if you want the plant material composted onsite and returned to your soil to help the remaining plants grow well and remain weed free.

After we have done weed control and mulched where needed, the Spring rush of weeds doesn’t occur for most species, and not at all if we have had time to eradicate the weed before the warm weather.

Instead, the wanted plants grow luxuriously in the moisture and sunlight of Spring, filling the space and reducing weed reinvasion.

Since we only started our business last Christmas, we don’t yet have photos of our clients’ gardens in Spring after our weed control.

Below is a photo of an area of public Reserve in January this year, hand weeded of major environmental weeds, then gradually of benign leafy weeds. This area is part of a forest margin, in which density is key to keeping the area weed-free, so native regeneration has been allowed to fill the space entirely.

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Finding the hidden treasures in Tradescantia

A native “Shaking brake” fern sporeling growing in Tradescantia

Almost every gardener knows Tradescantia ( Tradescantia fluminensis, aka Wandering Willie, etc). And many of them see it as a curse.

However, seedlings released from Tradescantia by careful handweeding usually include both natives and invasives, and they flourish in the humus created by decomposing Tradescantia.

The mahoe, toatoa, ti kouka, karamu and karo seedlings in the photos below are just a few of the thousands of native seedlings and sporelings we have found while handweeding Tradescantia in the Kaipatiki suburban area.

It is true that Tradescantia is relentless – though slow – in its growth, covering vast areas if unchecked, suppressing the natural regeneration of diverse native plants in wild habitats.

It is also true that it takes strategy and care to remove it completely and compost it to its extinction.

Above: Dense Tradescantia handgathered into piles for decomposition in place. Handweeding was begun furthest in the background, where the Tradescantia has been replaced by native regeneration 1-2 metres high.

Newly-piled Tradescantia around the cabbage tree is still green, while work has just begun on the area in the foreground.

Both before and after handweeding, Tradescantia’s leaves build up a loose humus-rich soil, and as a moisture-retaining ground cover it nurses seedlings and sporelings, which flourish if they are released to light at an appropriate time, and provided the soil is not allowed to dry out.

The humus and seedlings together provide for perfect regeneration of a native habitat if the Tradescantia is controlled methodically and carefully to its final eradication from an area, which can take a year or two as hidden stems emerge.

Below, June 2020: young toatoa (Haloragis erecta) seedlings, among the remnants and regrowth of Tradescantia after handweeding.

Many of these toatoa grew to a metre high here, helping revegetate a bank left bare by the removal of honeysuckle and dense Tradescantia.

Below, April 2021: The same bank, the toatoa on the right in foreground and midground. The young karamu, mahoe and ti kouka trees survived prolonged drought , sheltered and shaded by the shrubby toatoa that emerged spontaneously after handweeding of a major weed invasion which was followed by Tradescantia.

The image comparison below shows the same area during Tradescantia control in the foreground, as far as the tall ti kouka centre background. (The area beyond was left covered in Tradescantia for a few more years to avoid dessication and weed invasions more difficult to control, such as Creeping buttercup and Paspalum).

Drawing on our experience and photo records of handweeding for ecological restoration, we look forward to illustrating more examples as time permits.

In the meantime, you can see a description of our general methodology here.

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