April 2010 Issue
Once appreciated only by back-to-nature foragers, invasive Japanese knotweed is finding an ally in health-conscious cooks.
Recipe: Apple-Knotweed Pie
In the 100-plus years since Japanese knotweed was first imported from its native eastern Asia as an ornamental plant, it has proven to be a serious botanical menace.
Forget the gracefully arching stalks, heart-shaped leaves and lacy clusters of white flowers. Polygonum cuspidatum takes over wet, sunny stretches of disturbed soil — river and stream banks, roadside drainage ditches and vacant lots — growing up to 6 feet high and choking out anything that may have existed before its arrival.
Mark Bir, a horticulturist at the Cleveland Botanical Garden
, says the tuberous roots once considered useful in erosion control can grow over 3 feet deep and 20 feet in any horizontal direction in this part of the country, making the plant difficult to eradicate.
“In the last 20 years, it’s really run rife across the eastern United States and parts of eastern Canada,” Bir says. “It gets big quickly, and it will spread by underground roots quickly, too. It becomes a garden thug.”
But Wendy and Tom Wiandt have discovered an unexpected advantage to having Japanese knotweed on their 100-acre Wayne County farm: It makes a great side dish. Eight years ago, the proprietors of Killbuck Valley Mushrooms, a producer of oyster, shiitake and lion’s mane mushrooms, began experimenting with the tender, reddish-green shoots that appear each spring amid the bamboo-like remnants of the previous year’s growth. The couple enjoyed the tart, lemony taste of the greens, which they sauteed in olive oil and finished with a drizzle of vinegar and sprinkle of sugar. The next year, they began gathering “Japanese asparagus” to sell at farmers markets in the college town of Wooster and Cleveland’s trendy Shaker Square.
“I’ve got customers who will just steam the shoots — they say that Japanese knotweed reminds them of artichokes, the way it tastes,” Wendy Wiandt says.
The plant, once appreciated only by back-to-nature foragers, owes its growing appeal to more than just good taste. Researchers have discovered that fresh Japanese knotweed is an excellent source of resveratrol, that much-heralded polyphenol found in red wine. Dr. Michael Roizen, chief wellness officer at the Cleveland Clinic
, explains that resveratrol activates specific proteins that slow or stop a dangerous inflammatory process — a contributor to heart disease, stroke, memory loss and other “diseases of aging.” The resveratrol in red wine is negligible. And pill and capsule supplements are rendered inactive by exposure to oxygen. (“There is no company we know of that makes them in an oxygen-free environment,” Roizen stresses.) Yet a mere 1/10 ounce, or 2 grams, of fresh knotweed contains 300 milligrams of resveratrol, the estimated minimum amount needed each day to reap the health benefits of it.
“It’s the only food that’s got resveratrol in high enough concentrations for us to get enough of it,” Roizen says. “It concentrates resveratrol 40 times more than grapes do.”
Despite its anti-aging properties, aggressive proliferation and early-spring debut — the beginning of April to the beginning of May in Ohio, depending on the location — Japanese knotweed’s edibility is short-lived. According to Wendy Wiandt, the fast-growing shoots are tastiest when harvested at 6 to 8 inches high. Shoots collected at what she calls “the rhubarb stage” — 2 to 3 feet high — must be peeled, leaving relatively little pulp to savor. And in our admittedly limited experience, raw Japanese knotweed doesn’t freeze well for long periods of time. New York-based naturalist and cookbook author “Wildman” Steve Brill advises steaming, blanching or otherwise preparing knotweed in recipes before freezing to ensure it retains its flavor and texture.
But the culinary uses for Japanese knotweed continue to multiply: stir fries, soups, baked goods, jams and jellies, ice creams and sherbets, even wine. (Some cooks also use it as a substitute for rhubarb.) Roizen’s introduction came in the form of a research assistant’s apple-and-knotweed pie, the recipe for which was obtained from Brill’s Shoots and Greens of Early Spring in Northeastern North America (for details visit wildmanstevebrill.com
The pie is among the most healthful desserts Roizen has ever sampled. The filling is sweetened with liquid stevia, a calorie-free herb alternative to sugar or honey. And the unusual herbed crust — crispy, not flaky, as we discovered — is made with buckwheat flour and almond oil instead of the usual white flour and butter or shortening. Brill omits pre-baking the pie shell because, he says, “it’s more convenient, and it works.”
Apple and Knotweed Pie
Serves 6/Recipe courtesy of "Wildman" Steve Brill
Ingredients for crust:
2 cups buckwheat flour
1/2 teaspoon salt
1 teaspoon dried spearmint, ground
1 teaspoon coriander, ground
1/4 cup almond oil, or as needed
1/2 cup apple juice, or as needed
Ingredients for filling:
2 1/4 cups tart apples, peeled and sliced
1/4 cup Japanese knotweed shoots, sliced
1/2 cup apple juice
1 teaspoon liquid stevia
1 teaspoon cinnamon
1 teaspoon powdered ginger
1/2 teaspoon ground nutmeg
1/4 teaspoon ground cloves
1/2 cup sunflower seeds
1/4 cup each black walnuts and English (commercial) walnuts, or 1/2 cup English walnuts
3 tablespoons tapioca
Chill all crust ingredients. Mix flour with seasonings, then cut in oil until mixture is the consistency of wet sand. Slowly add apple juice until dough is elastic and pliable, but not mushy, and knead. Roll out dough and place in an oiled 9-inch pie pan, reserving excess dough for lattice top. Prick holes in crust with a fork.
Preheat oven to 425 degrees. Combine all filling ingredients and fill pie crust. Roll out excess dough and cut strips for lattice top if desired.
Bake for 10 minutes, then reduce heat to 350 degrees Fahrenheit and turn pie pan to distribute heat more evenly. Bake another 30 minutes, or until crust is crisp and filling is bubbly.