Prostrate Knotweed

Health Benefits

The old record — pyeonchuk (萹蓄). The Donguibogam lists the plant in the Herb section as 萹蓄 and records the vernacular name in the same form still used today. It gives a neutral nature and a bitter taste, notes that some call it sweet, and records no toxicity. It says the plant grows everywhere, that the seedling resembles fringed pink, that the leaves are fine and green like bamboo, and that the flowers rise between the joints and are exceedingly small. It was dug in the fifth lunar month and dried in the shade, and a further note reckons the plants growing by water and those bearing purple flowers the better ones. This is a historical medical record and differs from modern medical judgment.

Flavonoid analyses. Quercetin glycosides including avicularin have been isolated from prostrate knotweed in reported analyses. The same work also identifies tannin-class polyphenols. These are compositional analyses and have nothing to do with preventing or treating disease.

Where the names come from. The specific epithet aviculare derives from the word for a small bird, and the quercetin glycoside isolated from this plant took the name avicularin from the same root. The Korean name simply describes the flowers set at every joint.

Nutrition

• Avicularin (reported in the leaves and stems) — a quercetin glycoside named after this plant
• Tannins (throughout the plant) — polyphenols behind the astringency
• Silicic acid (reported in the whole plant) — a mineral component that stiffens the stems

Where you gather comes first Prostrate knotweed is commonest exactly where people and dogs pass — road verges, car park cracks, walking paths. That soil accumulates exhaust, animal waste and herbicide, so it is not gathered there. Pick a place whose treatment you know, such as a field edge or your own yard.

Shoots are blanched Young shoots go into boiling water, then a cold rinse, then the dressing bowl. Blanching takes the astringency out and brightens the colour. Grown stems harden at the joints and turn tough, so they leave the namul route and go to drying instead.

Quercetin glycosides and tannins Analyses report quercetin glycosides including avicularin isolated from this plant. The name avicularin itself comes from the specific epithet aviculare. Tannins account for the astringency. This entry stays with the compositional record.

How it is dried The Donguibogam specifies shade drying. Direct sun bleaches the colour to yellow and drives the aroma off, so spread it in a shaded spot with air moving through until it goes brittle. Once dry, snap it up by hand, seal it in a container and keep it somewhere cool.

Pairings

○ Doenjang and perilla oil — shoots as namul — Blanched shoots are dressed with doenjang and perilla oil. The salt of the paste settles the astringent finish. Sort out any stems that have hardened at the joints and use the soft tips alone.

○ Roasted barley or cassia seed — On its own the dried plant simmers to something plain, so roasted barley or cassia seed added to the pot brings a toasted note. Drop the heat once it boils, hold it at a gentle simmer, and strain when the colour comes. Barley · Sicklepod

○ Simmered plain — A handful of the dried plant in water over low heat makes a pale, clear tea. Brew it to a strength you would drink like water rather than concentrating it. Cooled, it drinks well through summer.

△ Gathering from verges and car parks — The places this plant is commonest are the places it is least safe to take. Road verges, car park cracks and dog-walking paths accumulate exhaust and animal waste, and herbicide is often applied there. Choose a gathering spot whose treatment you know, and keep herbicide off it.

△ Confusion with the smartweeds — Prostrate knotweed shares its family with the smartweeds and the young plants resemble each other. Smartweed leaves burn the tongue sharply when chewed and its flowers gather into a spike, while prostrate knotweed has no heat and sets minute flowers between the joints. Its fine green bamboo-like leaves are another point of difference. If you are not certain, do not gather.

△ A strong decoction every day — Simmering the dried plant strong and drinking it daily is closer to a habit than to food. If you are taking medication, settle the amount and the timing with your doctor or pharmacist. During pregnancy, making a daily habit of a plant that comes down through the old texts is best avoided.