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  • Tovin G.H.

Is This The Best Way To Control Invasive Knotweed?

Updated: Aug 17, 2022

Often dubbed "the godzilla weed," Japanese Knotweed and its cousins Giant and Bohemian Knotweed grow in massive monocultures, smothering everything in their vicinity.

But the secret to their strength may actually lie underground. Nearly every plant relies on the help of beneficial mycorrhizal fungi.

These fungi help find essential nutrients and minerals for the plants in exchange for sugars.

Knotweed is one the few plants that cannot form these relationships, so it ruins it for its neighbors. Knotweed exudes chemicals that suppress the growth of soil fungi (allelopathy) to take away the advantage that other plants have. However, these chemicals are not fully effective. The chemicals still allow some growth of beneficial fungi. This gives us a unique opportunity as land stewards to try to counteract the effects of the chemicals by boosting the numbers of soil fungi. Hopefully this will make up for the loss of fungal growth.

We decided to run an experiment to find out. First, we seperated the fungal spores from healthy forest soil using the flotation adhesion method. This was primarily to ensure that any effects that we noticed were from the spores and not from anything else in soil. In most other situations, healthy forest soil could be applied directly to plants. If you want to separate fungal spores yourself to concentrate the beneficial soil fungi, make sure to watch our video on the subject.

To finish the experiment, we applied the spores to the base of the native plants which were struggling against the knotweed. Hopefully this will boost the growth of native plants and help them compete. For the sake of experiment, we left half of the native plants untreated to act as a control.

As always, stay tuned for updates on the experiment!

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