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I have a problem with Kikuyu which feels like its "too hard" for me to deal with, and I'd be grateful for any advice, thoughts or productive comments. My property is in Auckland, New Zealand (approximate equivalent to US hardiness zone 9B I believe)

Kikuyu has taken over my property (I was blind to just how badly until recently - but in hind site this has been a problem in the making for longer then the 5 years I've been at the property). I have Kikuyu for lawn - which can be mowed and I expect I will have to live with, I also have a steep drop down to a very large pond which, when I refer to pictures, used to have native flaxes and other plants and is now overrun by Kikuyu. There is no way I can get a lawnmower down there - let alone my ride-on. When I started on it with a brush cutter there is a huge amount of runners acting like a mat which goes so far down (down as in layers - not down as in to the pond) I can't actually work out where it ends.

If I can weed-wack the green layers as well as say the top 10cm of runners , can I cover this mat of kikuyu with weed-mat and will it over time be able to turn into compost/soil? If this is doable, am I after some months (eg 6 months) able to cut holes in the weed-mat and replant? How long will a layer of weed-mat likely hold the kikuyu at bay, assuming I can keep the edge of the weed-matted area under control?

In addition to and/or in place of the above - and in the expectation that there is a clay soil underneath the kikuyu - are there any plants (particularly Native NZ trees and shrubs and fruit trees) and how big do they need to be to out-compete the Kikuyu around the bank/lake without a lot of regular maintenance - My goals here are too -

  1. Provide a shade and privacy to the pond area (so ideally stuff which is evergreen).
  2. Act as a carbon sink towards offsetting my CO2 emissions (for my own piece of mind, not commercially)
  3. If I can get fruit which I (and or the ducks and other wildlife) can eat that would be an excellent bonus.
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  • can you tell us what species Kikuyu is? – kevinskio Apr 13 at 11:45
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    @kevinsky - Kikuyu grass seems to be another name for Pennisetum clandestinum. In the US, it's listed as a federally noxious weed, which means it's a horrible invasive in most parts of the country. – Jurp Apr 13 at 13:15
  • Yup. Pennisetum clandestinum. – davidgo Apr 13 at 20:40
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Kikuyu grass is partly desired and partly invasive in California, which has prompted the University of California to create his fact sheet on the grass. Aside from all sorts of background information that you probably don't care about, the fact sheet does discuss methods of controlling an unwanted infestation. Among these are solarization if the area to be controlled is in full sun, black plastic to cut off light and water (which may be problematic in your terrain), and spot-treatment with herbicides to control the edges of a section of grass.

Weed-whacking the edges will have the opposite effect of control, as new plants can sprout from pieces of stolons cut up and thrown by the weed-whacker, and a porous weed-mat will probably have no effect on the grass.

You have a tough location due to the steep drop to the pond, which will probably rule out both solarization (if even possible due to the presence of a canopy) and black plastic. Note that the fact sheet ends with broadcast spraying of glyphosate being a viable means of control. You could do that, as long as you planted a cover crop of some type within a month of spraying on the hillside. Even if the grass were to regrow, the crop would have had time to mature and shade the area, making it harder for the grass to re-establish.

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