Inquiry on Testing and Safety of Knotweed from My Property - Ask Extension
Dear University of Maryland Extension,
I hope this message finds you well. I am reaching out to seek expert advice regarding a plant known as Knotw...
Knowledgebase
Inquiry on Testing and Safety of Knotweed from My Property #873363
Asked June 16, 2024, 8:27 PM EDT
Dear University of Maryland Extension,
I hope this message finds you well. I am reaching out to seek expert advice regarding a plant known as Knotweed (Fallopia japonica) that is present on my property. Given its reputation as an invasive species and its known uses in traditional medicine and culinary applications, I am interested in understanding whether the Knotweed on my property is safe for use.
Specifically, I would like to know:
1 Testing for Contaminants: Are there recommended procedures or services provided by the University of Maryland Extension for testing Knotweed for potential contaminants such as heavy metals, pesticides, or other harmful substances that could pose health risks if consumed or used medicinally?
2 Identification and Verification: Could you provide guidance on accurately identifying Knotweed to ensure proper species verification? Are there particular characteristics or resources available through the Extension that could assist in this identification?
3 General Safety and Best Practices: What are the general safety guidelines and best practices for harvesting and utilizing Knotweed? Are there specific parts of the plant that should be avoided, or preparation methods that mitigate potential risks?
4 Invasive Species Management: As Knotweed is known to be highly invasive, I am also interested in learning about effective management strategies to control its spread on my property while considering potential usage.
I appreciate any resources, recommendations, or testing services you could provide to ensure that the Knotweed on my property is safe and responsibly managed. Your expertise and assistance would be immensely valuable in guiding my approach.
Thank you for your time and assistance.
Best regards,
Rebecca
Prince George's County Maryland
Expert Response
Hello Rebecca,
Given its invasive and very hard-to-eradicate nature, we would not encourage that anyone keep Japanese Knotweed if it's growing on their property. It has already been found spreading into natural areas throughout Maryland.
Testing for contaminants may not be easy or cheap. We don't know who would test for heavy metals (though not many plants absorb those; lead, for example, tends to contaminate plants by way of contaminated soil clinging to produce or leafy greens surfaces, not because it's actually absorbed). Environmental testing labs can screen for pesticide residues, but they would need to know which exact chemicals to screen for, which is a very long potential list. Farms upwind could have had pesticide drift (airborne or water-washed runoff) move into other areas (though pesticide applicators are trained to minimize this risk when making applications), and prior use of the site where the weed is growing also would need to be taken into account.
Links included in the page linked above will help with plant ID; they contain photos for comparison as well as written descriptions of foliage, stems, roots, and flowers/seeds. Blooms/seeds can be very important for confirming plant ID when foliage can look like that of unrelated plants.
UMD Extension does not have information about the consumption or medicinal use of Japanese Knotweed. We can say that you should be absolutely positive of a plant ID before consuming or ingesting any wild plant.
Links in the first page linked also contain management tips, which tend to revolve around herbicide use to kill the roots. Multiple repeat treatments, potentially spanning a few years for a heavy infestation, may be needed, even using systemic herbicide.
Miri
Given its invasive and very hard-to-eradicate nature, we would not encourage that anyone keep Japanese Knotweed if it's growing on their property. It has already been found spreading into natural areas throughout Maryland.
Testing for contaminants may not be easy or cheap. We don't know who would test for heavy metals (though not many plants absorb those; lead, for example, tends to contaminate plants by way of contaminated soil clinging to produce or leafy greens surfaces, not because it's actually absorbed). Environmental testing labs can screen for pesticide residues, but they would need to know which exact chemicals to screen for, which is a very long potential list. Farms upwind could have had pesticide drift (airborne or water-washed runoff) move into other areas (though pesticide applicators are trained to minimize this risk when making applications), and prior use of the site where the weed is growing also would need to be taken into account.
Links included in the page linked above will help with plant ID; they contain photos for comparison as well as written descriptions of foliage, stems, roots, and flowers/seeds. Blooms/seeds can be very important for confirming plant ID when foliage can look like that of unrelated plants.
UMD Extension does not have information about the consumption or medicinal use of Japanese Knotweed. We can say that you should be absolutely positive of a plant ID before consuming or ingesting any wild plant.
Links in the first page linked also contain management tips, which tend to revolve around herbicide use to kill the roots. Multiple repeat treatments, potentially spanning a few years for a heavy infestation, may be needed, even using systemic herbicide.
Miri
