Gahnia Grove - Site summary and discussion's Journal

Journal archives for October 2018

October 6, 2018

Report for September 2018

Liaison: 1 hr; Monitoring: 2 hrs Weed-control: 7.5hrs
YTD: 34.5 hrs liaison and research; 53.5 hrs monitoring and documentation; 79 hrs of weed control; Total : 167hrs

Kikuyu has begun to grow again with the warmer weather, but has not yet been sufficient for "self-mulching by pullback".

In the Arena, Blackberry and honeysuckle roots continue to reveal themselves where not mulched, and have been either pulled out or mulched depending on soil conditions and their root strength. They are shortly to be uncovered throughout and assessed for either cutting/digging out, or ongoing rotting by mulching, depending on how they are found to be doing with current measures.

Weeds found and removed during the month include seedlings of privet, tree privet, climbing asparagus, Kahili ginger, cotoneaster, brush wattle, a few more previously hidden runners of honeysuckle under the manuka/kanuka, and a previously missed stems of Common ivy still at the stage of creeping on the ground..

The tree privets have had their new shoots plucked off (a 1-minute operation covered both trees) and branches bent down further where they have weakened.

A 3mH cotoneaster found under the manuka/kanuka canopy is to be ring-barked shortly.

There has been ongoing uprooting or mulching of Watsonia under the canopy throughout, and of Montbretia in the Arena.

Seedheads of Sonchus oleraceus from local grass berms (exotic but often referred to as "puha") have been scattered throughout the bared sun-exposed areas to help diversify the transitional plant community. It provides a little shade and soil stabilization, helps shelter native seedlings from wind, sun, animal interference and trampling, is very easy to remove if necessary, and when no longer needed becomes scant but nutritious mulch.

Wild carrot seed will be similarly collected and sown as soon as it matures. Seeds of one found in the Domain Rd end of the forest margin in winter were similarly strewn here, but may have been insufficiently mature.

A specimen of the indigenous "Esler's Weed", or Senecio Eslerii, was found near the Ngaio in the Domain Rd margin of the forest, and is being watched with the hope of collecting mature seed from it in due course. A native ragwort groundsel would make an excellent diversifier and habitat-creator!

https://inaturalist.nz/observations/17041763

Auckland Council is providing 24 hours of assistance by an experienced restorationist and contractor, to support the restoration of Gahnia Grove and such extension as we judge to be sustainable with the total volunteer long-term commitment of 2 hours weed-control a week.

Kaipatiki Project's Restoration Manager has confirmed that KP's overall planning of restoration of the margins of Eskdale Forest in the clearings and along Domain Rd and Glenfield Rd would be supported by Gahnia Grove being extended downhill through the canopy as far as the next clearing, and towards Domain Rd as far as the two Flame Trees which are to be removed. Weed control under the canopy avoids exposing an increased area to the risk of new or increased weed invasion, and will provide some weed material to be used as a protective barrier along the outer margins.

Maintaining the additional margin to the Flame Tree will require ongoing contractor assistance due to the uncertain contours and the amount of earth that could be exposed by controlling the present honeysuckle and blackberry.

Planting of quick-growing trees such as kanuka and karamu is likely to be beneficial on this margin, to establish shade as quickly as possible.

The slippage of that bank, once further revealed by the weed control to be started this month, will require further assessment after weed removal, as it may require stabilisation and/or fencing of the walkway at that point.

Annexe - Accidental vehicular interference?

The shrub/tree weed-pile on the outer edge of the Annexe has been eliminated, and some fine grass clippings introduced, along with two wide wheel ruts a metre or two into the Annexe, one of the ruts about 10cm deep.

The pampas mulch of the previously mown grass in the Annexe has been displaced, and the total volume of mulch seems to be less, so maybe the pampas mulch somehow got shredded in the same manner as the introduced shredded grass.

We are looking forward to a replacement mulch-pile to use as a border to the annexe, allowing ongoing restoration of native revegetation by clarifying the boundary for contractors and Reserve users.

Posted on October 6, 2018 03:59 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

October 8, 2018

Results so far on the partial-breaking and breaking-down of tree/shrub weeds

In answer to a query "how's this technique working out so far?":

Firstly, the trial is based on intuition and previous casual experience; ie this technique has been found elsewhere to be a practical solution on small juveniles in shade, when its not easy, or is undesirable, to uproot them - eg on a bank prone to erosion, or where their complete removal would disturb the roots of other plants.

In our casual experience to date on other sites, after a year or so of yearly treatment, small juveniles in shade have been found to have weakened enough to be pulled out with little effort or soil disturbance.

Elaeagnus, abundant along the path through Eskdale Forest in dry ground, still aren't easily pulled out a year or two after this treatment. But they don't grow significantly, so it is a practical solution for bush-walkers who can identify them; it only takes a few seconds to stop them taking over the next bit of understory in the next year (and becoming too thorny to handle).

Here are all observations of Ligustrum spp, ie Tree and Chinese privets, in the Gahnia Grove site, in order observed, including all re-observations after interventions.

Luxuriating in full morning and partial afternoon sun, the 3-4m Tree privet in Gahnia Grove, in June 2018 and in Aug 2018, showing numerous buds and branchlet regrowth after 3-4 months. However, it can be "broken down" again in a matter of seconds, as all branches are within reach. It's then easy to knock off the buds and break back any new branches.

The longest were found in October, about 30cm long but still soft enough to be broken back easily.

So far, on the big ones like this at Gahnia Grove, in a dense native planting in which these tree privets had overtopped and were suppressing the adjacent native trees, it takes less than a minute to prevent them being an immediate threat to the expansion of its native neighbours. This has been done approx monthly since July so at this stage can't be recommend ed for eg an annual programme. (though it may well result in less regrowth than felling).

It remains to be seen what the longer-term results will be with the monthly one-minute de-budding and knocking-back.

Also being trialled at Gahnia Grove is ringbarking combined with lower-branch removal, on one about 3.5mH that was too tall and rigid to be pulled down. Leaving the top growth on helps starve the tree, we suspected and have had confirmed by others.

The tallest one here, its lowest branches partially broken and bent down, and its trunk ringbarked, in Mar 2019 shows no new growth in the top part, but has put out new shoots just below the ring-barking. At least these are easy to reach! But they will impact on adjacent trees if not controlled.

Posted on October 8, 2018 05:41 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 2 comments | Leave a comment

October 13, 2018

Expanding the restoration site

Paul, an experienced restoration contractor/biosecurity management student with some experience of staged, site-based (rather than species-based) manual control has spent 4 hours on the site, assisting with the weed-control according to the methodology being trialled. He has been contracted for 20 more hours over the next 10 weeks, so we will be extending the weeding as far throughout the canopy as time allows, removing pampas, grasses, Watsonia, Elaeagnus, cotoneaster and ginger and other weeds as encountered.

Plant ID
With Paul's eyes on-site, some additional plant identification was done, including confirming a suspected, apparently isolated invasion of Polygala myrtifolia (2 specimens here, none observed elsewhere in the reserve so far). The seedlings were under canopy, spindly, and had not grown perceptibly since first observation 6 months ago. They were removed.
https://inaturalist.nz/observations/13730071
https://inaturalist.nz/observations/14035171

iNat had already helped , leading to a suspected ID but the plant could not be removed until this was confirmed, in case it was a native not kown to me. So it was a relief to have this confirmed and not have to let the plants mature to flowering for an iNat ID.

Gahnia Grove
The arena was cleared of its areas of mulch, which was composed of the mixed kikuyu and Japanese honeysuckle that had previously covered the area. The live honeysuckle and balckberry roots revealed were pulled out.

Removal of mulch also allowed the Calystegia to be broken off at ground level from these areas, as had already been done in the rst of the arena, and along the canopy margin. The soil in the unshaded arena is now too dry for significant amounts of underground runner to be uplifted with the leafy stems, so follow up on the Calystegia will be required regularly through the summer. It is an easy weed to remove (above ground), but kills small trees by occluding all light, and can also pull trees c.1.5m H to an almost horizontal position as it grows over the top of them then fastens itself to something on the other side.

Kikuyu was just long enough for a modest "pullback" the length of the arna-kikuyu margin, and a few places along the outer planting.

The big pampas in the Annexe planting, having been reduced by cutting and pulling down to about 1m H, received a good trampling to aid its decline.

Smaller pampas in the canopy were trampled or pulled out, along with a few honeysuckle runners recently emerged.

An assessment was made of Cape Honey Flower (CHF) Bank, strategies to control the honeysuckle, blackberry and CHF there, and the need to avoid baring a great area of clay to summer sun. Since there is no expectation of contractor assistance after December, and this steep unstable bank is physically challenging, the strategy used will have to avoid leaving plant material on top of live honeysuckle, making it more difficult to access for control. However, the blackberry would probably weaken with being mulched over.

The challenge will be to work with these three densely interwoven weeds to

  • access and release the few native trees on the bank from honeysuckle (increasing canopy),
  • reduce the density of CHF and limit their further spread, and
  • eradicate, if possible, the blackberry

and in the process to

  • create areas where native regeneration can occur, while
  • minimising increased sun exposure.

The CHF trunks are light and make good movable mulch, but if dropped on top of honeysuckle would require removal later - to be avoided. It may be possible to use the CHF wood as a moisture-retaining mulch down the side of the bank, adjoining the Arena, where it will be possible to access it if needed to control the vines.

Update: Re whether CHF is a nectar supply for birds, and how it spreads:
http://www.terrain.net.nz/friends-of-te-henui-group/weeds-by-scientific-names/melianthus-major-cape-honey-flower.html

So we can remove all flowering parts at no cost to birds, (who might in fact be poisoned by it).

Posted on October 13, 2018 05:10 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Cape Honey Flower

Was researching whether Cape Honey Flower is a nectar supply for birds, (re whether the removal of a large stand adjacent large nectar-producing trees ,also to be removed, needs to be staged to avoid disrupting food supply) and how it spreads.

Found the answers here:
http://www.terrain.net.nz/friends-of-te-henui-group/weeds-by-scientific-names/melianthus-major-cape-honey-flower.html

It seems it spreads vegetatively, and waterways and oceans carry seeds.

All parts of the plant are extremely poisonous. Both people and animals have died from ingesting it, and birds may be affected.

So we can remove all flowering parts at no cost to birds, and reduce its possible spread at the same time.

Posted on October 13, 2018 07:03 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment