Japanese Knotweed

A Misunderstood Healer

Last week, I celebrated Earth Day in New York City with talks and walks focusing on medicinal plants that thrive in the urban wild. Abandoned lots, alleyways, sidewalks, and city parks are teeming with beautiful healers — so-called weeds like mugwort, dandelion, burdock, plantain, and Japanese knotweed. Valuable food and medicine. Shifting our perception of weeds and invasive species can foster intimacy with nature in the city and change the way we interact with the land under our feet.

As more forests and land are destroyed, the presence of invasive species and so‑called weeds will only increase, so we must learn who these plants really are before attacking them.

Japanese knotweed is a tall herbaceous perennial with the ability to thrive in toxic soils, drawing out heavy metals and poisons to detoxify damaged land. With an extensive woody rhizome system, the plant can set up whole underground systems that can grow inches a day, moving beneath highways and around obstacles to set up colonies on the other side.

This pervasive plant learned to thrive in the harsh environment of Japanese volcanoes amid extreme changeability and grows successfully on the lava fields lining the slopes of Japan’s active volcanoes. Knotweed developed the ability to store explosive energy deep underground and spring forth through feet of ash and volcanic rock and can break through seemingly firm foundations to create feral instability. But as this plant dismantles, Japanese knotweed creates soil that is fertile and new. 

Japanese knotweed roots contain nature’s highest source of resveratrol, a botanical hormone that resembles female sex hormones, which, not surprisingly, gives knotweed fierce regenerative power. Even a tiny, tiny rhizome can grow into an entire plant, and if left to do her thing, she can spread quickly and relentlessly underground. Japanese knotweed habitats range from parking lots, roadside embankments, forest edges, disturbed grounds, and volcanic deserts to much of the industrialized world.

In the United Kingdom, Japanese knotweed has gotten a bad rap as something of a supervillain in some quarters, particularly with landlords who are convinced that this plant destroys homes and degrades the value of land they perceive to be theirs. Often referred to by the media as “Britain’s largest female,” Japanese knotweed first spread throughout the country after German botanist Phillipp von Siebold sent a small cutting to Kew Gardens in 1850. All the knotweed in Britain grew from the underground rhizomes of this one single plant. But the plant’s reputation as a supervillain is overblown. According to a recent report by the House of Commons Science and Technology Committee and ecologist Dr. Mark Fennell, “We found nothing to suggest that Japanese knotweed causes significant damage to buildings— even when it is growing in close proximity.” But because of her bad reputation and incredible resilience, people pour millions of dollars and copious amounts of toxic herbicide into the ground to get rid of her. The only true beneficiaries of this smear campaign are the chemical companies that produce glyphosate and other toxins (the real supervillains, in my opinion) that kill not just knotweed but the surrounding wildlife and have been shown to cause cancer. Meanwhile, the properties of knotweed have been shown in numerous studies to prevent and treat cancer.

It is in the plant’s native Japan, where knotweed is known as itadori, whose translation is “remove pain,” that people have been living in harmony with this plant for thousands of years. The roots and shoots have become an integral part of food culture and traditional medicine. The young stems are eaten as a spring vegetable, with a flavor similar to incredibly sour rhubarb. The roots are used to treat a variety of ailments ranging from fungal infections and skin inflammation to cardiovascular diseases and pain, as the name suggests. Japanese knotweed has a strong immune-enhancing capacity that benefits the cardiovascular system and has been shown to have anti-cancer, “anti-aging” (I take issue with that term) and estrogen-regulating effects. 

A recent study by Harvard Medical School showed that resveratrol taken from knotweed rhizomes stimulates in humans the production of a serum that blocks diseases by speeding up the cell’s energy production centers, affecting the activity of enzymes called sirtuins that control several biological pathways and are involved in the aging process.

Tincture and decoction of the root have also been shown to kill the spirochetes (spiral-shaped bacteria) of Lyme disease that are found in difficult‑to‑reach areas by enhancing blood flow throughout the body. And though this organism, Borrelia bacteria, which we now call Lyme, seemed to appear just over forty years ago, a recent study by Oregon State University found a fifteen‑to‑twenty-million-year-old piece of amber from the Dominican Republic that is the oldest fossil evidence of Borrelia fossilized in amber and shows that this bacteria has been around for about fifteen million years— long before humans walked the Earth. 

Lyme disease is named for its epicenter in Lyme, Connecticut— an area with an imbalanced predator‑to‑prey ratio. Ecologists have linked that ecological imbalance and its domino effect with the rampant spread of the disease. In a recent interview, herbalist Stephen Harrod Buhner, author of Healing Lyme, said that “this disease is forcing people to break out of the allopathic medical paradigm because it doesn’t work for Lyme.” In order to truly heal, we need to examine the root causes of deeper, persistent illness and resolve the ways we abuse and exploit our ecosystem.

The negative perception of plants like Japanese knotweed fuels a profitable war on invasive species contributes to more ecological damage and increases our adversarial relationship with the living Earth. Learning about a plant’s community dynamics and species niches is crucial to helping us understand the motivation of so‑called weeds or invasive species. If a plant is doing harm, we need to explore the reasons why they are thriving: Where are the ecological gaps? What species of plant or animal might be missing? If there are absences, can the missing links be safely and effectively reintroduced? What are the human practices surrounding the ecosystem? Are those practices overwhelming and killing the native plants? If so, can the community be educated and practices shifted for the well-being of all? If there is no clear underlying cause and a plant is truly overwhelming an environment, are there alternative uses for the plant such as food, medicine, or biofuel? Invasive species are not inherently evil, and the short-term “solutions” of herbicide can have dire long-term consequences that cause the greater community of plants, animals, and people even more harm than the emergence of the plant itself.

Maybe instead of poisoning plants like knotweed, we can pay attention.