PITTSBURGH—During lunch at Six Penn Kitchen, a fancy downtown restaurant, diner Scott Michael put a forkful of sauteed green shoots into his mouth and chewed. “Crunchy, sour, green,” he said. “I do like it a lot.”
He was eating Japanese knotweed, a savagely invasive plant that thrives on riverbanks and vacant lots, both of which Pittsburgh has in great abundance. Tougher to eradicate than coal dust, knotweed can grow 6 feet a month in the spring, stand 13 feet tall when full-grown and stretch its roots 15 feet.
It even grows through asphalt and concrete, shading out other plants until entire landscapes are knotweed only.
Pittsburgh and many areas around it have so much knotweed that businesses are turning it into beer, paper, kimchi, tinctures, ice pops and honey. At least a half-dozen upscale restaurants have served knotweed, which has the texture of asparagus and tastes like rhubarb. The plant’s reputation as a menace only enhances its appeal.
“It’s like if you can’t beat it, eat it,” says Valerie Testa, a community gardener and professional landscaper who has unsuccessfully battled knotweed in her yard and neighborhood.
Volunteers at Healcrest Urban Farm enjoy ice pops made by blending strawberries and knotweed. ‘Everybody is trying to think of unique ways to get rid of it,’ the farm’s owner says.
The bamboo-like plant, with reddish stems and heart-shaped leaves, arrived in the U.S. from East Asia by way of the United Kingdom in the late 1800s. Knotweed was originally admired as an ornamental ground cover—and cover the ground it has.
“Any piece of abused land that we’re not doing anything with is fertile ground for it,” says Art Gover, head of the Wildland Weed Management program at Penn State College of Agricultural Sciences in University Park, Pa. “It’s going to thrive anywhere where you don’t have routine maintenance, which is most places.”
Another out-of-control Asian import, kudzu, is sometimes made into jelly. It was planted for erosion control in the Great Depression but then overran the rural South.
Wild Purveyors Wholesale LP, a supplier of local ingredients, sold 260 pounds of knotweed to 13 different customers last year, up from just three customers in 2014, says co-owner Cavan Patterson, 38 years old. Last year’s biggest customer was a brewery that made 15 barrels of knotweed saison, a type of ale.
Knotweed sales so far this year total 120 pounds. His price has held steady at about $8 a pound. “Knotweed is an invasive species, and eating it is beneficial to the environment,” he says.
The plant grows right around the corner from the Wild Purveyors warehouse, but Mr. Patterson won’t pick knotweed anywhere in Pittsburgh because it absorbs whatever is in the ground. That includes lead from abandoned homes, water from polluted rivers and various toxins from shuttered industrial sites.
Otherwise, knotweed is high in vitamin C and a major source of the antioxidant resveratrol.
“At this point, it’s getting some infamy. Everybody is trying to think of unique ways to get rid of it,” says Maria Graziani, co-owner of Healcrest Urban Farm in Pittsburgh’s Garfield neighborhood. She blends and freezes the plant into strawberry knotweed ice pops that sell for $3 to $4 each.
Across town in the light-filled kitchen of her fifth-generation family home, Christina Joy Neumann set out a jar of knotweed honey that her bees made from the invading plant’s stringy white blossoms.
The honey is “Guinness-like, very dark and earthy, smooth and grounding,” says Ms. Neumann, the owner of Apoidea Apiary. Last year, she flew to San Francisco to receive a Good Food Award for her rosemary knotweed honey, which sells for $6.75 wholesale and as much as $12 retail.
“I was taught that is it such an evil plant, and now I’ve come to really like it,” she says. To her, buzzing bees and the scent of knotweed flowers now feel synonymous with “a nice mid-August evening.”
On a recent foraging trip, Mr. Patterson drove 42 miles to a park along the Conemaugh River in the small town of Blairsville, Pa. He parked at the head of a 1.7-mile trail.
Knotweed was the only undergrowth along the trail’s entire length. The stems and leaves seemed to close in around his hiking companion, triggering fears of plague and invasion.
Mr. Patterson knelt down, flicked out his knife and began cutting tender knotweed shoots that were 10 to 15 inches high. He filled a laundry bag with 31 pounds. Pausing to look around, he said: “You can barely tell I was here.”
Five pounds of Mr. Patterson’s harvest were soon headed for Six Penn Kitchen, where executive chef Kevin Hermann had begun experimenting with knotweed the previous Saturday. “It tastes the way a lemon smells when you squeeze it,” said Mr. Hermann, 35.
That night, he served a knotweed-rhubarb compote for dessert. Three days later, he made an entree of knotweed and scallops.
Standing under heat lamps in Six Penn’s open kitchen, Mr. Hermann tore the leaves off the knotweed and diced its shoots into thin cylinders, sauteing them with mushrooms. He served that over the scallops with celery root purée and a watercress salad with red wine mustard-seed vinaigrette.
For a private event the next day, he used knotweed shoots in a sauce over oysters. “I love cooking with things people can’t just go to the store and buy,” he says. Now that Mr. Hermann cooks with knotweed, he notices it everywhere.
Ms. Testa, the community gardener and landscaper, says she gets annoyed when she sees knotweed on restaurant menus because “that doesn’t bring any awareness to the ecosystems it invades and disrupts.”
At Penn State, Mr. Gover gathers knotweed to stir-fry from a patch near his office. He likes it but says eating knotweed isn’t a viable form of control. “Who needs thousands of acres of garnish?” he says. “Nobody’s that hungry.”