Japanese Knotweed

Polygonum cuspidatum

Also known as Itadori, Hu Zhang, Fallopia japonica, Reynoutria japonica, Mexican bamboo

At a glance

Family

Polygonaceae (the buckwheat and knotweed family)

Type

Herbaceous perennial with tall, hollow, bamboo-like canes

Parts used

Root and rhizome (young spring shoots are also eaten as food)

Size

3 to 10 feet tall, spreading widely underground by rhizome

Bloom

Late summer into early autumn, in airy sprays of tiny creamy white flowers

Habitat

Riverbanks, ditches, roadsides, and disturbed ground almost anywhere in the temperate world

Acquisition

Forage

Traditional remedies in HerbSense

Key benefits

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Traditionally supports circulation

Historically eases joint discomfort

Rich natural source of resveratrol

Traditionally used to clear heat

Traditional uses

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In Chinese medicine the root is known as Hu Zhang, 'tiger's cane,' and has been used for centuries to invigorate blood flow, clear heat and dampness, and support the lungs and liver. In Japan it is called Itadori, meaning roughly 'remove pain,' a name that speaks to its long folk use for aching joints and bruising. Long before Western science took an interest in its resveratrol content, village herbalists were digging the autumn roots and simmering them into dark, earthy decoctions. The young red-flecked shoots have also been gathered as a tart spring vegetable, cooked much like rhubarb, in both Asian and more recently Western kitchens.

How to grow & use it

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Pairs well with

✦Turmeric
✦Ginger root
✦Dandelion root

Substitutes

✦Rhubarb root
✦Turmeric

Choose it when

“For the stubborn ache that circulation forgot, and the heat that needs somewhere to go.”

Did you know?

Japanese knotweed root is one of the richest natural sources of resveratrol, the same antioxidant compound found in red wine, and for years it was the primary commercial source for resveratrol supplements before the industry largely shifted to grape skin byproducts. It is a strange bit of irony that a plant so despised by gardeners for cracking pavement and crowding out riverbanks was quietly stocking apothecary shelves the whole time.

Safety

The root can act as a laxative in excess and carries oxalates, so people prone to kidney stones should be cautious. It's traditionally avoided in pregnancy and may interact with blood thinners like warfarin due to its effect on liver enzymes and clotting.