STORY. This shot of kahili ginger overgrowing native forest on
Waiheke Island is a graphic reminder of what can happen when aggressive
weeds are ignored. Fortunately here on GBI the situation is still
favourable for eradication of unwanted weeds provided action is taken.
Our feature article on weeds highlights the work of the Barrier D.o.C weed
team and makes a plea for public assistance in detecting sites of weed
infestation. The colour shots of the “unwanted four” on the rear cover
should aid in positive identification.
An update on weeds and weed control on Great Barrier
So what’s a weed anyway? A weed is a plant growing where it is not
wanted and having a harmful impact. This impact can range from kikuyu
grass smothering the vege garden, to gorse taking over a paddock,
through to pine trees battling it out with kauri in areas that were
logged in the old days — it’s a broad term!
There are lots of names for harmful plants: pest plants, noxious weeds,
environmental weeds etc. But these all amount to the same thing: plants
with harmful impact, so for simplicity we just call them weeds.
Why is D.o.C worried about weeds?
Weeds often get a foothold in areas with lots of sun and disturbed soil.
Great Barrier, with it’s vast stretches of coastal cliffs, sand dunes
and wetlands are perfect spots for weeds to put down roots. Once weeds
get established in these sorts of areas they jostle with the native
plants growing there to get the most light — unfortunately, it’s often
the weeds that win!
The ‘unwanted eight’!
D.o.C is working with the Auckland Regional Council to nip the following
weeds in the bud on Great Barrier: Kahili ginger, woolly nightshade,
smilax, climbing asparagus, tree privet, grey willow, boneseed and
madiera vine. On our neighbouring Waiheke, these weeds are really well
established and they can only be managed on a site by site basis. On
Great Barrier we have the opportunity to get these weeds entirely off
the island, rather than them being with us forever.
This work has been going on for a number of years. D.o.C has been working
north of Tryphena and the ARC have funded work in the Tryphena area. In
the past couple of years Brett O’Reilly and his Envirokiwi team have
done this work on contract for the ARC. D.o.C pull together a team of
weeders each year. Jordon Scarlett, Hiku Davies, Nathan & Johan Laven,
and Niki Wii all worked on the D.o.C weed team in the 07/08 year. They
were led by Alex McDougall who had just returned from doing weed work on
Raoul Island for a year.
A big part of trying to stop these weeds get established is finding them
before they produce seed each year — easier said than done! Basically,
the D.o.C & ARC teams look for these weeds by lining up a metre or two
apart, doing a sweep through an area until no more weeds are found,
turning around, sweeping back etc. The vast majority of time is spent
just looking for the plants. In most cases, we dig these weeds up, bag
them and take them to the Claris tip. This way we know they’re not going
to regrow from tubers or roots. Then comes the task of going back to
check for seedlings that come away from the stocks of seed in the soil.
Lots of places where these eight weeds grow are on private land. D.o.C and
the ARC are grateful to all landowners who have supported the drive to
get these eight nasty weeds off the Barrier by allowing us to look for
them on their properties.
What other weed control does D.o.C do?
Other than looking for the eight weeds discussed above, the D.o.C weed
team also tries to keep on top of weeds on the reserves that D.o.C
administers. Again, a big focus is trying to catch small patches of a
wide range of weeds before they take hold. In other cases the team chips
away at weeds such as pampas grass that are well established on the
In the 07/08 year some of the big projects for the weed team were
treating pampas in the lower Kaitoke swamp, on the dunes at Whangapoua,
and further north in Te Paparahi. Pine trees were felled around the
wetland opposite the Police station. Pines were also controlled along
the forest road, and in other areas of central Great Barrier. In some
cases, the scale of these jobs is too big for the spade, and plants are
sprayed/treated with herbicide. When herbicides need to be used, the D.o.C
weed team use the safest herbicide for the environment.
Where to go for more info on Weeds:
If you’d like a weedy plant from your garden identified, ideas on
controlling weeds, or further information on the work D.o.C does on weeds
on the Barrier, feel free to call George Wilson at the D.o.C Office on 09
4290 613. If you have access to the internet, you may want to check out
the ‘weedbusters’ website:
www.weedbusters.co.nz or the D.o.C website
www.doc.govt.nz If you want
information on how to control weeds check the ARC site:
How you can help minimise the impacts of weeds on GBI.
• Give us a call if you think you may have seen any of the ugly eight
weeds we’re looking for,
• Purchase plants from the nurseries on island. That way you avoid other
weeds (and pests like argentine ants) hitching a ride over from the
• When you do bring plants from the mainland — carefully remove any
seedlings growing in the potting mix before bringing them.
• Control widespread weeds such as pampas grass, sweet pea and
cotoneastor on your property to slow their spread on the island.
• If you do control weeds — think carefully before disposing of them. If
you’re dealing with a known weed with seed on, or tubers — the best bet
is to take the material straight to the Claris landfill. Don’t dump
weeds on the side of the road — there are many places on the island
where weeds are spreading after being dumped.
WEEDS to watch out for on Great Barrier Island
Grey Willow (Salix cinerea)
Boneseed (Chrysanthemoides moniifera)
Tree Privet (Ligustrumlucidum)
Woolly nightshade (Solanum maritianum)