Kikuyu control June 2018-May 2019

Both maintained mown and long wild kikuyu have been successfully eradicated from the entire site except the Annexe* lawn, which still holds mixed grasses containing some kikuyu.

Eradication of unmown kikuyu from the downhill Arena Bank:

followed by eradication of mown kikuyu from the "Arena Top":

More views of the Arena over the last year:

The outer boundary of Gahnia Grove, bordered by a 3-10m wide roadside path and recreational area of regularly mown kikuyu, has been similarly controlled with the suspension since June 2018 of all contracted services, ie line-trimming, herbicide and mowing, in the cordoned area.

A strategy to maintain the boundary kikuyu-free remains to be established. Council supplied us with 3 cu m of wood chip mulch in December 2018 to cosmetically cover low loose piles of woody weeds then being used to suppress kikuyu, and to help define the area of suspension of mowing during the pullback process.

This mulch has considerably assisted the widening of the kikuyu-free margin, by several metres in places, to achieve the shortest possible margin for ongoing manual contrrol. The mulch was laid, in most of the margin's then-65m length, as a 50cm wide border 10-20cm deep, with wider and deeper piles where areas of kikuyu eradication needed to be expanded. The amount applied has been ideal, sufficient to control the kikuyu growth at the boundary while limited enough to move around when stolons needed to be reached to pull back, forcing attempted growth in the opposite direction.

Mulch is no longer required where kikuyu has been eradicated to a straight line, but is being retained within the kikuyu-free border for future suppression of the expected scattered new growth from deep rhizomes, likely to occur until shade is established by canopy along the boundary.

Letting the new growth advance into the presently kikuyu-free border in its usual form in these conditions, ie long unrooted or superficially rooted stolons, would eventually allow pullback onto the currently bare area of border. This might be seen as a lack of control of the kikuyu, but actually prevents incursion. It does, however, create an unruly appearance when compared to the sharp line of a neatly mown lawn edge.

About 10m of margin has now the mulch withdrawn, leaving the mown edge neat and flat, without the tufts of vigorous new growth that continue to occur where the mulch oninues to be used to expand tge area of eradication. We can now experiment with strategies for the disposition of the regrowth into the kikuyu-free area, looking for a visually attractive and soil-conditioning method of ongoing control of kikuyu within a restoration or planted border along a mown edge, if such a thing is possible.

In wet season, once roots are rotted, long kikuyu pulls back easily mixed with its attached topsoi. This material will ideally replace wood-chips as mulch here, and provide a receptive growing medium without material cost.

*(The Annexe lawn is mostly Axonopus fissifolius and paspalum dilatatum, and the lawn has been and remains suppressed by mulching with pampas, manuka brush and decaying honeysuckle vine, with kikuyu being pulled back as it emerges. In the wet season, if and when it occurs, these mixed grasses are expected to rot under the mulch, as occurred last winter in part of the lawn similarly mulched).

For those who have not long been following this kikuyu management trial, the following may be of interest, posted in November 2018 on the Gahnia Grove Umbrella Project Journal:

A number of observations have been made specific to the management of the kikuyu invasion of the forest and planting margins generally in Eskdale Reserve's Upper Forest margin, and documenting the management of these margins in Gahnia Grove.

For clarity and detailed ongoing monitoring, these have been divided into (in order of development over time - ie CHF Bank and Flame Tree Bank were only cleared of honeysuckle in November) the mown kikuyu margins of:
The Arena
The Apron
The Annexe
CHF Bank
Flame Tree Bank

Also being hand-weeded, hopefully to be formally included in the area for suspension of edging services, is the Annexe canopy/Top Clearing margin of mixed exotic grasses incl. kikuyu:

Posted by kaipatiki_naturewatch kaipatiki_naturewatch, June 20, 2019 03:26


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