The Truxor vehicles, an amphibious cross between a tractor and a tank, are armed with giant rakes to remove the carpet of Crassula helmsii – also known as New Zealand Pigmyweed – that is covering the man-made serpentine lake at the Surrey garden.
The non-native weed reproduces rapidly and, without natural competition in the UK, can quickly spread out of control, overtaking a waterbody and blocking out light for other flora and fauna.
The harvesters have been busy collecting the weed and depositing it in a huge pile on the island in the centre of the lake. Here it will rot down quickly, creating compost, while allowing any fish and invertebrates scooped up to make their way back into the lake.
It could take nearly two weeks for gardeners to clear the surface of the invasive weed and there is no known way to get rid of it completely. Claremont gardeners will manually remove the weed throughout the year using nets and waders.
Senior gardener Tim Rayfield said: "By using the large harvesters, we’re able to control the Crassula with minimum impact on the lake and its eco system.
"It’s one of the more unusual ways that we conserve this amazing landscape garden, and it’s great to be able to see the trees reflected in the water once again."