Japanese Knotweed

Polygonum cuspidatum

Fallopia japonica


Native to Japan, North China, Taiwan and Korea, Japanese knotweed is considered one of the world’s most invasive species. The plant arrived on British shores as an ornamental in 1825 and in the U.S. a few decades later. It has now spread to 39 states and to Canada, New Zealand, throughout Europe and the British Isles, Russia and Australia. Stephen Harrod Buhner points out knotweed's ability to grow from even the smallest pieces of root as being much like the Lyme spirochetes it is often used to treat.

Known also as Mexican Bamboo, Japanese Bamboo, Chinese Bamboo, Fleeceflower, hu zhang (Chinese), kojo and itadori (Japanese), hojang (Korean) and Hancock's curse. There are somewhere between 65 - 300 species in the genus, and many of them have been used medicinally for thousands of years with similar, interchangeable effect.

Japanese knotweed is widely used as a food source. The young spring shoots are gathered in spring when less than 8 inches tall and cooked as you would asparagus, or sweetened with sugar in a manner similar to its cousin, rhubarb. The taste is sour, due to the presence of oxalic acid, and the outside fibrous layer is tough, so for culinary use the shoots need to be peeled. Like rhubarb, it is a good source of vitamin C, and eating large quantities has a gently laxative effect. The mucilaginous nature of the plant makes it soothing to the stomach and intestinal tract and its mild acidity also helps to ease digestive woes. The roots are often prepared with complimentary sweet fruits such as apple, to create delicious and medicinal jams and chutneys. Culinary use is contraindicated for those with inflammatory conditions such as gout.

The antioxidant actions and flavanoid content of Japanese knotweed roots are found to be higher than onion, carrot, broccoli and ginger. Japanese knotweed contains high concentrations of resveratrol, the same heart protective substance found in grapes, and they have been used to treat cardiovascular disease in Japan for centuries.

Japanese knotweed is strongly antibacterial. It is active against a number of both gram positive and gram negative bacteria, A and B Streptococci and twenty different strains in this genus. It also helps to counter E. coli and Salmonella typhi, in part due to its ability to inhibit bacterial DNA primase.

Studies have found Japanese knotweed to have antiviral activity as well. It is an especially effective ally to call on when dealing with a number of viruses, including H1N1, various flu viruses, herpes simplex and HIV, among others. Its action is actually two-fold; it limits replication of the virus and also eases inflammation in affected tissues and systems.

Japanese knotweed enhances immune function and is particularly protective of the endothelial cells which line the interior surface of blood and lympathic vessels, especially in the brain. Crossing the blood-brain barrier, it has a calming and anti-inflammatory effect on the central nervous system and is especially protective of the brain in cases of inflammation and bacterial infection. It shuts down pathways that spirochetes utilize to generate the most damaging cytokines, limits Herxheimer reactions and helps to protect the heart.

A typical medicinal dose is 20-30 drops of tincture added to a bit of water. Knotweed increases blood flow to places of the body which are typically difficult to reach, such as  the eyes, heart, brain, spine and joints. It works synergistically with other herbs when taken in combination, bringing them into these areas as well.

Japanese knotweed is particularly useful in cases of Lyme disease where its broad range of actions travel throughout the body to reduce inflammation, protect healthy tissues, increase microcirculation, promote antiviral and antibiotic actions throughout the body systems, enhance healthy immune function, reduce autoimmune reactions and enhance the performance of other herbs and medicines.

The herb contains at least 67 known compounds and condensed tannins, most notably resveratrol, trans-resveratrol, emodina and polydatin.

In tens of thousands of studies done on knotweed, results consistently highlight its ability to  protect the brain from recurrent strokes, combat the effects of chronic stress, ease neurological symptoms in cases such as Parkinson’s, decrease the healing time for burn victims and reduce burn shock, as well as its ability to inhibit the growth and spread of cancer by preventing blood flow to tumors.

The Koreans traditionally use Japanese knotweed to improve oral health. It helps prevent the formation of plaque, breaks up existing plaque bio-films and acts as a health-bringing toning agent to the gums. An infusion of the roots is typically used as a mouth wash and often held in the mouth for five to ten minutes, once a day. Alternately, if you use a water pik, you might add 10 drops of tincture to the water in the tank, or use the infusion instead of water, to bathe your teeth and gums.

In Traditional Chinese Medicine the roots are used to reduce heat in the body and to invigorate and clear the blood. It is used specifically for difficulties in menstruation and after childbirth, to treat jaundice, skin wounds, bites, psoriasis and a wide range of infections. In India and throughout Southeast Asia, the leaves are used in a smoking mix.

WARNING! This herb is contraindicated when taking blood thinning agents and during pregnancy. Discontinue use ten days prior to surgery.

Flower Essence Japanese knotweed helps clear limiting beliefs, especially those that limit healing or belief in one’s ability to heal.

Magical Lore Keep a bit of Japanese knotweed root in your pocket or magical bag during dark times. It will give you the strength and endurance you need to hold out for the light.

Culture Japanese knotweed is a tall, voraciously spreading plant with jointed hollow, woody stems. The young shoots are red spotted and yellow green when still small and then turn entirely red as the stalks grow and mature. The leaves are alternate, large and heart shaped and the plant produces long stems of creamy flowers that emerge from the leaf axils in August and September. The flowers are beloved by many pollinators and especially honey bees – the resulting honey will be dark and full-flavored, similar to that of the chestnut flower. The plant is able to reproduce by seed, which looks like tiny dark brown fruits surrounded by a papery wing-like outer edge; but this is unusual, because finding a fertile male plant outside of the far east is rare. The plant produces numerous underground runners which are capable of spreading incredibly far from the parent plant and will sprout up even through concrete. Once the plant has established a presence it is near impossible to eradicate. 

Years ago, when I first settled on the land we call Blessed Maine Herb Farm, I transplanted a clump of Japanese knotweed roots at the edge of my garden. I thought the plant was magnificent looking, and still do, and wanted some nearby. I planted comfrey roots and day lilies around the edges of the clump. Forty years later, the Japanese knotweed has not taken over my garden space, though the clump has grown into a beautiful stand. It’s been held in check by those other plant roots. The dense root systems of knotweed make it particularly effective for erosion control in damaged and wasting landscapes. Its ability to remove heavy metals from industrial damaged sites makes it an important plant for bioremediation and a powerful soil restorative. Note: the plant should not be harvested for medicinal use when growing in such conditions.

Knotweed will grow in any type of soil but prefers waste places and the edges of streams. It appears that all European plants are the clones of a single female. The Japanese Knotweed Alliance says that this makes the plant, "one of the biggest females in the world in biomass terms." We harvest the roots in late Fall or early Spring. No matter when you dig them, it’s a workout and a lot of hands, and muscle, are needed. They do not come out easily by any means! We tincture the roots in alcohol after cutting them into small pieces, using a sharp axe to do so. Whatever roots we don’t tincture immediately, we lay out on screens to dry. Stored properly, the dried root can remain potent for several years. The roots are especially susceptible to breaking down from sun and light exposure, so are best stored in a brown paper bag in a cool dark place after drying.

Actions: Antibacterial, Antiviral, Antischistosomal, Antispirochetal, Antifungal, Immunostimulant, Immunomodulant, Anti-inflammatory,

Angiogenesis modulator, Calcium Channel adaptogen, Central Nervous

System relaxant, Central Nervous System ( brain and spinal cord)

protectant and antiinflammatory, Antioxidant, Antiathersclerotic,

Antihyperlipidemic, Antimutagenic, Anticarcinogenic, Antineoplastic,

Vasodilator, Inhibits platelet aggregation,

Antithrombotic, Tyrosine kinase inhibitor,

Oncogene inhibitor, Antipyretic, Cardioprotective, Analgesic,

Antiulcer, Hemostatic and Astringent


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