Japanese Knotweed (Polygonum cuspidatum, Fallopia japonica)

Sumo Wrestler
Japanese Knotweed, painting

DESCRIPTION: In the early spring, Japanese knotweed looks like an army of nondescript fat, green, red-flecked stalks poking up from the ground. While the underdeveloped young leaves don't provide uch of a clue to the plant's identity, last year's dead stalks do: the new shoots grow among a bamboo jungle of jointed (Polygonum means many knees), hollow, lightweight wooden poles up to 13 feet tall, even though the plant belongs to the buckwheat family, not the bamboo family. The mature Asian ornamental bears large, triangular, smooth-edged, alternate (singly configured) leaves, 4 to 6 inches long and 2 to 4 inches wide, with pointed tips (cuspidatum means "make pointed") and straight bases. The mature reddish stems form a zigzag pattern.

Arising from where the leafstalk meets the stem (the axil), the tiny white flowers, blooming in late summer and fall, form such beautiful, long, lacy spikes that gardeners imported this "weed" from Japan.

Giant knotweed (P. sachalinense), also edible, is taller, with larger leaves with heart-shaped leaf bases. I've seen it only once, in Bronx River Park. There are no poisonous look-alikes.

Giant Knotweed Shoots

Besides providing delicious flavors for recipes that benefit from a sour component, giant knotweed contains a natural pesticide,
MOI-106, with great potential for organic farmers.

HABITAT: Japanese knotweed grows on disturbed soil, along roadsides and riverbanks, in other moist areas, and in fields. Often displacing other plants and difficult to eradicate, it's so tasty that some municipalities have surrendered, and hold annual Japanese knotweed festivals instead.

Japanese Knotweed Skeleton

SEASON: You can eat Japanese knotweed shoots from mid-April to early May, before the plant gets tough and woody. Rarely, tender new edible shoots grow later, after the plantís been cut down.

Japanese Knotweed Shoots

FOOD USES: Best when 6 to 8 inches tall, the intensely tart, tangy shoots (discard all the tough leaves) taste like rhubarb, only better. A tough rind that you must peel (good for making marmalade) covers the taller ones.

Slice the stems, steam as a vegetable, and simmer in soups, sauces, fruit compotes, and jam, or bake in dessert dishes. Use sparingly. I've made terrific applesauce and excellent strawberry compotes using just 1 part knotweed to 10 parts fruit.

You may even substitute cooked knotweed, which gets very soft, for lemon juice, transforming familiar recipes into exotic ones. Or use a chopstick to pierce the membranes that separate the segments of 1-foot-tall shoots, peel, stuff the stalks with sweet or savory stuffing, and bake in an appropriate sauce.

NUTRITION: An excellent source of vitamin A, along with vitamin C and its cofactor, the antioxidant flavonoid rutin, Japanese knotweed also provides potassium, phosphorus, zinc, and manganese. Itís also an excellent source of resveratrol, the same substance in the skin of grapes and in red wine that lowers LDL (bad) cholesterol and reduces the risk of heart attacks. When I find the plant on tours with school classes, I tell the kids that the plant prevents heart attacks, and we do an experiment: I have a teacher, whom we all observe carefully, eat some knotweed. Then I proclaim: "See, he's not having a heart attack. it works!"

Resveratrol may delay the onset of Alzheimer's disease or slow its progression. Normally, glial cells in the brain support the neurons (nerve cells) and apparently modify the way they communicate, but in Alzheimer's disease, an accumulation of gunk called amyloid plaques signals these helper cells to kill the neurons instead. Resveratrol seems to block this deadly signal. And resveratrol will also increase your lifespan by 30%, but only if youíre a fruit fly. It activates sirtuin genes, which increase cell longevity the same way a calorie-restricted diet does. Whether this might also slow human aging is still open to question.

Japanese Knotweed Shoots
MEDICINAL USES: Large quantities of Japanese knotweed act as a gentle laxative, like rhubarb.
Japanese Knotweed in Flower

FEATURED RECIPE: Apple and Knotweed Pie