Harris Gunnera Control

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The ongoing battle with the Gunnera Tinctoria, continues. With support from the Community Councils and funding from Scottish Natural Heritage, the North Harris Trust is co-ordinating a pilot project seeking to identify the best methods for halting the spread of Gunnera. We also aim to update our distribution maps and to look at the options & costs for a full scale eradication scheme.

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A team from OH-MEET (Outer Hebrides- Managing Employment, Enterprise & Training), has started spraying outlying populations of Gunnera and weather permitting they will attempt work around Scalpay, Scaladale, Ardhasaig, Rhenigidale, Leverburgh and Flodabay. In the meantime North Harris Trust Staff and volunteers have continued to work in and around Tarbert.

Eradicating Gunnera from Harris is going to take a large scale, co-ordinated effort, involving professional contractors and teams of volunteers. None the less, every Gunnera plant removed will reduce the rate of spread. If you can help, especially by dealing with plants on your own property, it could make all the difference. Here is some guidance on the methods we would recommend.
1. Manual Digging
Especially effective on seedlings and young plants, it is often surprisingly easy to dig up mature plants using a sharpened spade. Just be aware that the whole of the swollen ‘turnip like’ root needs to be removed or the plant will regenerate and if the seed heads are mature, they must be carefully bagged and disposed of in your organic waste bin or at the Urgha re-cycling centre.
2. Chemical Treatment
The most effective, widely-available chemical for spraying Gunnera is Glyphosate. This is commonly sold as ‘Round-up’, although there are other brands. This should be applied according to the manufacturer’s recommendations, ensuring good spray coverage of the entire plant. Alternatively the herbicide can be applied as a stump treatment. i.e. cut all of the leaves just above ground level and then paint the herbicide onto the exposed wounds. This method is particularly suited to plants near watercourses and/or if it is too windy to spray, or if there is a threat of rain. Again, follow the manufacturer’s recommendations for mixing and applying stump treatment. The solution used for stump treatment is much stronger than that used for spraying, but overall much less chemical is required, as the application is more targeted. Make sure your mixed herbicide is safely contained by using a ‘weed-wipe’. Once you are finished each plant it is a good idea to cover the treated stems with the cut leaves to protect the treatment from rainfall. The best time for treating Gunnera with chemicals is late in the growing season (late Aug/Sept), when the plants are fully grown, before the leaves die back.

Whichever method is used, follow up treatments are likely to be necessary. Gunnera is very resilient and if the plants have reached maturity, their seeds will be in the surrounding area and are likely to germinate. However, every time the plant is treated it will get weaker, it will produce little if any seed and will be more susceptible to the next treatment. So don’t be disheartened, if the plant re-grows, just give it another go. If you don’t have the time or the equipment to remove Gunnera from your land then you can help by just removing the seed heads. At least this way you can effectively limit the spread of Gunnera.
We strongly discourage Harris residents from intentionally growing Gunnera tinctoria because of the now obvious risk. In Scotland, it is legal to grow Gunnera in your garden. However, it is an offence to allow it to spread onto neighbouring land.
For further information on this project, or if you have any suggestions for dealing with this pest please contact Gordon Cumming, Land Manager at The North Harris Trust. Tel: 01859 502 22 or email: gordon@north-harris.org

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