DESCRIPTION: In the early spring, Japanese knotweedÝlooks like an army of nondescript fat, green, red-flecked stalks poking up from the ground. While the underdeveloped young leaves donít provide uch of a clue to the plantís identity, last yearís dead stalks do: the new shoots grow among a ìbambooî jungle of jointed (polygonum means ìmany kneesî), hollow, lightweight wooden poles up to 13 feet tall, even though the plant belongs to the buckwheatÝfamily, 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 4º inches wide, with pointed tips (cuspidatum means ìmake pointedî) 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 ìweedî from Japan.

Giant knotweedÝ(P. sachalinense), also edible, is taller, with larger leaves with heart-shaped leaf bases. Iíve seen it only once, in Bronx River Park. There are no poisonousÝlook-alikes.

SEASON: You can eat Japanese knotweedÝshoots 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.

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 sparinglyóIíve 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, ìSee, heís not having a heart attackóit works!î

Resveratrol may delay the onset of Alzheimerís disease or slow its progression. Normally, glial cells in the brain support the neurons (nerve cells), but in Alzheimerís 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.

MEDICINAL USES: Large quantities of Japanese knotweedÝact as a gentle laxative, like rhubarb.

FEATURED RECIPE: Apple and Knotweed Pie