A Giant Hogweed infestation at South Norwood Country Park in Croydon, which was causing serious contamination of Chaffinch Brook, is being treated using equipment supplied by Stem Injection Systems (Europe).
Thames 21, one of the country's leading waterway charities, works with communities across Greater London to improve the quality of local rivers, canals, lakes and ponds. It has invested in six to sets of stem injection equipment to treat this and other waterway sites where invasive, non-native plant species are a problem.
Over the past four years, its 12-man treatment team has been fully trained in use of the equipment and problems such as this Giant Hogweed outbreak are part of its ongoing treatment work.
As a large seeding plant, Giant Hogweed can spread quickly via wind or waterways and, as a result, is a particularly common problem along rivers and canals. This was the case at Chaffinch Brook where some 1,000 individual plants have already been treated and killed using stem injection.
Vic Richardson, habitat and restorations officer at Thames 21, said: "Stem injection has proved the ideal treatment method and Stem Injection Systems has continued to provide valuable support and advice. The equipment enables us to identify isolated stands, inject glyphosate-based herbicide directly into each plant's hollow cane and avoid the potential watercourse contamination that might be caused by, for example, pesticide spraying methods.
"We rotate our treatment work ever two or three weeks so we can monitor the results and inject any plants that were initially missed or treat any new Giant Hogweed growth. Last year in one half mile section of the river we probably treated some 200 plants, this year it's down to just 20 or 30. Although this suggests we have the Giant Hogweed infestation under control, we never underestimate the plant's ability to spread or become complacent about the scale of the treatment challenge."
Thames 21 has also successfully used the equipment to treat Japanese Knotweed, including recently on a large area of the River Pool in Sydenham.
"Easy to use and very effective, the stem injection system is a vital piece of kit in our treatment armoury," says Richardson. "Its portability means that if our team identifies an isolated stand of knotweed whilst out on a river system improvement programme, it can be dealt with immediately within treatment guidelines."
