Weed assessment update
Kahili ginger
A new technique has emerged to rapidly suppress any fruiting ginger stems observed during our exploration and removal of Tradescantia.
A bulky mass of Tradescantia suppresses growth by its weight and by light occlusion, and its moisture content significantly enhances the rotting process.
Clumps of ginger with up to about 20 stems have been effectively and easily suppressed by:
-bending and/or breaking the stems, in several places if necessary, until all parts of the plant were contained within a diameter small enough to completely cover with piled Tradescantia from nearby.
The resulting piles ranged from c. 40x40cm D for 2-3 stems, to c. 1.5m D for a large clump.
No emergence of leaf or stem was observed in subsequent weeks or, at Gahnia Grove, over subsequent months.
After a month or two, uplifting of the Tradescantia piles reveals partially-rotted stems still attached to partially-rotted tubers.
Tubers at this stage have been largely unrotted and hence viable, but their rotting roots uprooted easily, allowing reburial of the uplifted tubers near the top of the Tradescantia pile re-placed over remaining tubers.
We are monitoring several piles of Tradescantia rotting ginger in this way, and have so far observed removal of several tuberous masses weighing several kilos each (observations to be uploaded as time permits).
We hope to be able to re-observe the remaining clumps to discover the time required to rot ginger clumps to eradication by this method, quicklyt and esaily done ad hoc as ginger is encountered, with no tools, no poison, and minimal physical effort.
(cf In our other Trial Site "Gahnia Grove", this method is effectively controlling Alocasia and Arum lily, and greatly assisting Japanese honeysuckle eradication from a prescribed area).
Moth plant
A new, and much the largest, invasion was found throughout the top of a mahoe c.10mH at the stream edge, within 50m of the Madeira in the tanekaha. From the opposite, Witheford-side stream bank, the vine was barely visible, but many pods were observed.
This has been communicated to Ecocontract managers, who by study of service maps have determined that the entire Kaipatiki Roadside bank, despite being a Sensitive Environmental Area, is Auckland Transport land, not a formally-defined Reserve, and therefore was not covered in any weed-control contracts.
We have been told that the Ecocontract for Witheford Reserve is now being modified, or another contract created, to cover the Kaipatiki Roadside streambank for control of the same General Reserve target species as Witheford Reserve.
On the Kaipatiki Roadside streambank the species present and now to be targeted include Madeira, Moth plant, ginger, and Phoenix palms once they reach a certain size.
Tree privet, Woolly nightshade, Wattle
A few Tree privet and Woolly nightshade and Brush wattles may be small enough to be addressed under the Ecocontract, but most specimens of these are large trees requiring arborism. We do not consider the few individuals present to present a significant threat to restoration of native vegetation, providing there is ongoing monitoring with removal of seedlings and juveniles, particularly on sunlit margins and any areas where there has been extensive removal of ground cover, eg Tradescantia.
On the roadside, it will include many juvenile Tree and a few Chinese privet, many of them however already suppressed by our ad hoc interventions without any tools during surveys over the last year. These suppressions are proving surprisingly effective so far on trees up to about 2mH, and on larger trees where the leader was able to be partially broken.
We have since purchased a folding saw and are now able to effectively suppress trees up to 4mH. This is done only with consideration of the needs of nearby native vegetation, ie to release space for the anticipated spread of adjacent natives, while contionuing to provide soil stability, habitat and partial canopy. From our observations so far, we would expect follow-up of these trees by the same methodology to keep them under 2mH, developing only minimal foliage and succumbing to stress over a few years.
We would like to determine how many years that would take. Our correspondence with a Texan volunteer in Tree privet control suggests that ring-barking of all major branches results in death within 1-3 years, with retention of the upper part of the tree resulting in earlier death than in felling.
We have marked for ongoing monitoring a few of the Tree privet we have thus treated. There are many more in the roadside canopy margin. If this Project is to be funded ongoing we would mark some of those for monitoring also, provided we can communicate their locations and marking method to the Ecocontractor prior to their own control operation. We have now marked with orange tape several dozen juvenile tree privets and two Chinese privets that were suppressed by "partial breakdown" either in an ad hoc intervention in August 2018,or subsequently during this Trial. The Ecocontractor is aware and will inform team members working in either Witheford Reserve or the adjacent roadside.
Tree weed control Tradescantia Trial Zone
Within our Tradescantia Trial Zone we have cut or broken down several juvenile wattles, woolly nightshades and tree privet.
Wattles
Wattles cut down have died without any sign of regrowth.
Woolly nightshades
Wooly nightshades cut down developed leafy shoots from their stems, and were broken down again (it only takes a few seconds to snap or partially-cut the stem).
Two woolly nightshades are about 5mH and contributing to canopy over native understorey (observed valuable last summer and autumn during the drought). They would be easy to ringbark. We would recommend this for a gradual replacement by native canopy, and if time permits will seek approval from the Community Ranger to do it ourself, or liaise with the Ecocontractor for their consideration of the issue. (We note there are many more pressing issues of Tree privet and other weed control on this stream bank)
Phoenix palms
Those seen currently along the creek are up to about 60cmH. Loopiong the leaves in a circle and pulling tiinto a know takes only a few seconds, no equipment, is soil-friendly, has so far been effective over more than a year at Gahnia Grove and Kaipatiki Creek, and we recommend it to suppress further growth and probably weaken the growth.
Unfortunately the Target Species for General Reserves do not cover these:
Japanese Honeysuckle
Invasions have been found in the upstream area centred midway up the bank where there are no native trees, eg where a pine was felled in 1999, and reaching almost to the streamside.
Elaeagnus
Many dozens of small seedlings have been broken off or uprooted (depending on size and soil conditions) from streamside banks, forest and roadside.
Juveniles and adults alike are numerous throughout the upsteream banks. Those within the Trial site are no longer evident, having been suppressed by our Trial method was encountered.
Specimens treated this way from June 2018 to June 2019 are now either uprootable (if small) or barely grown since the intervention. As we come across them we repeat the intervention, suppressing them further. Larger trees require either more extensive, more frequent (eg quarterly) or more repeated, (eg annually for several years) interventions before growth becomes negligible.
Elaeagnus trunks to c.8cmD are soft and easy to cut with a small folding saw. A specimen several metres high and spreading several metres through native canopy beside the Native Plant Trail was sawn through easily, leaving its diffuse vine-like branches firmly supported in the adjacent kanono and mahoe as the foliage wilted.
Elaeagnus without intervention provided abundant fruit throughout July at several nearby locations observed from the Native Plant Trail.
Cretan brake
The invasive fern Cretan brake has been found in a number of locations and either uprooted or suppressed in each location. The smallest were able to be uprooted, and a larger one was uprootable after breakdown and suppression. The largest, about a metre high and wide, was trampled and mulched but would require a few follow-up interventions to eradicate it.
Bangalow
A number of mature or almost-mature abangalows now line the stream, and seedlings are being found in the streambanks themselves as well as in forest. We have obsedrved the seeds on sloping pavements above gutters in our neighbourhood, and assume that many of them roll into the stormwater system and are carried into the streams in this way, in addition to the bird-borne invasions.
Madeira
The Madeira vine spotted flowering throughout the tops of dying and dead tanekaha hasnow been observed more closely from the opposite streambank, where it climbs from the sandy bank into mamaku, mahoe, tanekaha and other trees. From our distance of c. 10-20m acors the stream we did not see any sign of vine strangling the several tanekaha, and assume death was by light occlusion or from other causes.
A Madeira tuber was found in Tradescantia at the roadside above, (Zone Ea) 10-20 metres from the vine visible in the outer edge of the c.20mH casnopy of tanekaha/kanuka/mahoe/karo on the Kaipatiki Roadside streambank in Zone Fa.
Weeds found in Tradescantia
While juvenile tree/shrub weeds and mature vines are scattered to common in the Tradescantia-covered areas, exploration and removal of dense Tradescantia has disclosed few hidden weeds at any stage of development, with the following exceptions:
-runners extending nearby invasions of Japanese honeysuckle and Calystegia silvatica (probably x sepium)
- Madeira, a small vine extending from a nearby canopy invasion, through extensive blackberry, into moderate Tradescantia growth covering dry ground
- Ehrharta erecta creeping from dry roadside into deep Tradescantia, where it is hidden but establishes and matures where Tradescantia coverage is thin
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