Weeds Never Sleep by George Wilson

Environmental News Issue 15 Winter 2008

COVER 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 island.
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: www.arc.govt.nz/plantsearch
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 mainland.
• 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.

NOXIOUS WEEDS to watch out for on Great Barrier Island

Grey Willow (Salix cinerea)
Boneseed (Chrysanthemoides moniifera)
Tree Privet (Ligustrumlucidum)
Woolly nightshade (Solanum maritianum)