Mahinepua Radar Hill Landcare Group

Weeds in our area

Below you can find details and pictures of some of the worst weeds that occur in our area.
 
More detailed information about weeds is also available from the following websites.
landcare logoTouchwood BooksNzpcn banner
www.nrc.govt.nz
www.landcareresearch.co.nzwww.touchwoodbooks.co.nzwww.nzpcn.org.nz
  

Touchwood Books, in conjunction with Weedbusters have published
“The Weed Control Handbook.
  How to Identify and Manage Invasive Plants in New Zealand”

At $30.00 this should be a mine of useful information.
weedcontrol

 
There are also a set of free guides by region at the Weedbusters site.PlantmeinsteadWeedbusters.org.nz - Plant Me Instead Guides

Melianthus major or Cape Honey Flower

This is a smelly clump-forming shrub with hairy frond-like leaves and dark reddish-brown flowers. It spreads via suckering roots into large clumps and it is poisonous. Its seeds, which are long-lived, are also water-borne and to a lesser extent wind-borne. It can smother low growing coastal species, forming large stands and destroying habitats and often leads to subsequent invasion by weedy vines. It likes sand dunes, sheltered coastal and steep areas, estuaries, inshore islands, disturbed lowland forest margins, shrubland and fernland.To get rid of it you can dig it out and dispose of the roots at the tip or burn them or cut down and paint the stumps with Tordon. The roots re-sprout profusely so follow-up treatment will be necessary


Cotoneaster glaucophyllus

This is a problem because it competes with native shrubs and is quite happy growing in the most inaccessible places. It will grow into a small tree and is rapidly spreading throughout the area.  You probably saw the numbers of plants on the side of the Whangaroa Road this winter. The red berries are carried by birds and the plants quickly establish in the bush or any semi open area. They have a very long taproot and can be controlled either by pulling out when they are small or by cutting and applying, within 15 minutes, 5g metsulfuron-methyl (600g/kg e.g. Escort) per 10 litres of water. Alternately spray with Escort.

Gorse – Ulex europaeus

Gorse is one of the most widespread of all pest plants in New Zealand. It is a perennial problem for many of us because the seed remains viable for a long time; some say up to 100 years. J
And just when you think you have a handle on it, up it comes again. Persistence is the only way to treat this pest!
There are various ways of controlling gorse, mechanically, chemically and by using a biological control.
Mechanically (or manually) you can dig it up or pull out seedlings, or cut it close to the ground and paste or paint with Vigilant or Glyphosate
Chemically you can spray it using Escort, Tordon or other recommended sprays. Attention needs to be paid to the instructions on the container as to dilution and the time of year. Glyphosate works well on very young gorse.
You can also get Tordon in granular form, which is easy to apply, and you don’t have to worry about drift from spraying.
Biologically there are various agents available that can be introduced and you can find out more about these from Landcare Research.

 


Solanum Mauritianum  or Tobacco Weed
Also known as Wooly Nightshade, Kerosene Plant, Flannel Leaf or Sodom’s Apple.
 
This has long been a pest in the North but thanks to continued efforts by members of our group (and particularly to Fred Barnes who can spot one at half a kilometer and attacks it immediately) it is not so prevalent in our area at present. However it does pop up regularly as the seed is spread by birds – especially pigeons. It is a weed because it grows and matures rapidly, it is allelopathic, i.e. it produces toxins that poison the soil, it inhibits regeneration of native plants and is not fussy about growing conditions.
To control it you can pull up small plants when the soil is damp. Larger plants can be cut down and the stumps painted with Tordon at the rate of 100ml per litre or using Vigilant gel. Alternatively spray the whole plant with a Tordon based spray.

Ageratina riparia, commonly called Mistflower  (Narrow pointed leaves) and Ageratina adenophora, commonly called Mexican Devilweed, (Larger rounded leaves and larger flowers)

Both of these plants are common in our area and can become very invasive. They like a wide range of habitats but prefer warm, wet, semi-shaded areas. The seeds are mainly dispersed by wind and water and existing plants spread by layering of low-growing branches. They smother emerging native species and are a major weed of stream banks.
Biological control can be used by introducing Entyloma fungus and gall-fly.
Alternatively you can pull the plants. However small pieces of root will re-grow.
Or use chemical control by applying Glyphosate with a penetrant or Metsulfuron with a penetrant. Best time for this is between August and January
Ageratina ripariaAgeratina adenophora
 

Lantana camara 

This very nasty weed is very much in evidence in our area and gaining in numbers all the time. It is nasty because the seed is spread by birds that drop it in the bush and before you know it there is a plant up to 6 metres wide, straggly, prickly and with an unpleasant smell. It is time-consuming to get rid of because of its sprawling habit and, unchecked, can quickly cover large areas. This was rarely seen in the Core Area but recently quite a number have found their way over the hill and been dealt with quickly.

 

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