Knotweed Herb

Knotweed Herb

Knotweed is a popular herb. The whole flowering plant is used to make medicine. This plant is an invasive species yet has been used traditionally in Chinese and Japanese medicine for its benefits on gastrointestinal health and circulatory health (among some other claims such as cancer prevention). The herb has the ability to outgrow and suffocate the growth of other plants. The plant produces a flower that appears from August to September, as well as a fruit. The plant, native to Japan and other Asian countries, was brought to the U.S. through Britain.


This is a shrub-like herbaceous perennial, 1 meter or more. Underground rhizomes is decumbent, woody, yellow, and with obvious knots. Stems are erect, cylindrical, hollow, and with glabrous surface scattered with many red or purplish spots. Leaves are alternate, broad ovate to nearly oblong, 7 to 12cm long, 5 to 9cm wide, and with short pointed apex and rounded or cuneate base. Petiole is 1 to 2.5cm long. Membranous sheath is brown and caducous. Small but dense flowers are unisexual, dioeciously, and with auxiliary panicles. Pedicels are long and with wings in the upper part.


The underground part of the herb has already been used as medicine for thousands of years, mainly for treating Lyme disease, cough, joint pain, chronic bronchitis, jaundice, amenorrhea, hypertension, and so on. In addition to its extensive medicinal uses, it is also cultivated as ornamental plant and cooked as food too. Its edible parts, including edible leaves and shoots, are eaten as vegetable. And its root is used for making refreshing cold drinks to replace tea in summer.


As a supplement dosage for an adult usually 2-4 grams of the dried herbal powder is advised. As a therapeutic dosage sometimes 6-10 grams per day – taken in divided doses – is used. For a dosage of more than 10 grams per day it is recommended to do so only under supervision of a doctor.


Taking Japanese Knotweed at high doses can thin the blood work, it is recommended not to use it within 10 days for surgery, along with blood thinners. Large dosages or long term usage can be toxic to kidneys.