Urban nature educator Zack Rouda asks us to put aside our prejudices against Japanese knotweed and view the invasive plant in a fresh light: As a potential meal.
“It looks like Jurassic asparagus,” Rouda says in a 3-minute online video titled “How to Eat Japanese Knotweed,” where he gets up close to the early shoots and demonstrates how to harvest the plant, which is native to East Asia but now thrives around the world. Japanese knotweed often shows up in neglected spots, and here in Maine the shoots emerge in May.
Rouda, director of Portland-based Rewild Maine, argues that the plant has some uses. He notes in the video that pollinators like honey bees and butterflies “love it,” and that it helps control erosion. Beyond those, “it’s edible,” he says on the video. “It’s high in a bunch of nutrients, including resveratrol. It’s tasty, and we can do a service to the land by picking every single shoot.”
The shoots Rouda is referring to are the tender early spring growth that emerge asparagus-like and quickly grow into thick stalks that resemble bamboo and can reach 10 feet high.
“The rule is you snap it and if it makes a popping sound and is clearly tender, it is good to eat,” Rouda said. “If it is woody and papery, you can move up to the top and snap off the tip.”
In his food foraging guide “Wild Plants of Maine,” naturalist Tom Seymour writes that “even when the shoots attain a height of several feet, they can still be used, if we pick only the tender flexible tip.” Seymour has harvested Japanese knotweed in Maine for at least 50 years. “It is among the easiest plants to harvest, no tools needed, just snap the stem,” he said in an email. “Identification is no problem and it doesn’t even require much bending, so it is easier to gather than most other wild plants.”
In late summer, the plant produces lacy, white flowers. The pleasing flowers and overall shape of the Japanese knotweed plant explain why it was imported to America in the 19th century as an ornamental. But being one of the world’s most resilient plants, it promptly escaped into the wild, where it outcompetes native plants and creates monocultures, according to many biologists.
Before picking Japanese knotweed, harvesters need to be aware of possible pollution issues. Because knotweed often grows in ditches and along roadways, plants in such spots are likely growing in soils contaminated by lead and other heavy metals, which the plant will accumulate in its stalks. Foragers should also be aware of possible pesticide contamination.
The state of Maine characterizes Japanese knotweed as “widespread” and “severely invasive.” Because it is so difficult to eradicate, the Maine Natural Areas Program recommends land owners eradicate it by applying the controversial herbicide glyphosate, sold under different brands, the best-known of which is Roundup. The World Health Organization in 2015 labeled the pesticide a probable cause of cancer in humans, and municipalities such as Portland and South Portland have banned its use.
Because Japanese knotweed spreads from its roots, or rhizomes, harvesters who dig the roots need to be meticulous in gathering all that they unearth, according to Nancy Olmstead, the invasive plant biologist at the Maine Department of Agriculture, Conservation and Forestry.
“The greatest risk of spreading Japanese knotweed is when you dig up the roots,” she said. “When you are finished digging, you need to cover up any area you disturbed and bring with you all pieces of root that came out of the ground.” (Do not compost them in home composting systems.)
Olmsted advises harvesters to gain permission from landowners before harvesting and to remember that within Maine State Parks removing plant material is prohibited. However, foraging for plant-based foods is permitted without a permit on Maine Public Lands, as long as harvesters “leave enough to reseed and feed wildlife,” according to the Bureau of Parks and Lands. In every other case, foragers need to take only a portion of any stand of a particular plant. But as Rouda indicated, harvesters can pick every Japanese knotweed shoot they see, since most landowners want to get rid of it.
Japanese knotweed, which also has medicinal uses (the plant brims with the powerful antioxidant resveratrol and has become a standard herbal treatment for Lyme disease), can be eaten sweetened, like rhubarb, or as a vegetable, like asparagus. Like rhubarb, it’s tart with a somewhat lemony taste.
A few years ago, Rouda taught a class on knotweed at Root Wild Kombucha in Portland, and everyone went home with a jar of knotweed sauce. Rouda said none of his students had eaten knotweed previously.
“There were some people who knew off-hand that you could eat it, but had never done it. Then there were some people who had no idea what Japanese knotweed is.”
Rouda’s go-to preparation method involves harvesting the early shoots, removing the leaves and chopping the stems. He adds the chopped stems to a pot with water and sweetener, brings the mixture to a boil and simmers it until it cooks down like applesauce. He puts the sauce on yogurt or ice cream. Rouda also dehydrates knotweed to make fruit leathers.
“You can make a great knotweed pie by cooking it with sugar, the same as rhubarb,” Seymour said. “Also stewed knotweed, with sweetener, is delicious.”
But Seymour’s favorite way to eat it is as a vegetable, simmering the chopped knotweed shoots or tips for a few minutes in water until they turn tender and a lighter shade of green. After draining them, he serves the shoots simply – with butter, salt and pepper.
Avery Yale Kamila is a food writer who lives in Portland. She can be reached at avery.kamila@gmail.com
Twitter: AveryYaleKamila
Jars of tangy Japanese knotweed sauce ready for eating. Photo courtesy of Rewild Maine
Knotweed Chutney
Reprinted with permission from Tom Seymour’s “Wild Plants of Maine,” and modified to be vegan by using maple syrup instead of honey. You’ll need canning jars and lids to make the chutney. Seymour describes the recipe as “a lot of work, but well worth it.”
Makes 7 (eight-ounce) jars
Gather together:
2 pounds Japanese knotweed stem tips, cut into inch-long sections. Use tender young shoots, or if using larger stems, peel them, discarding any stringy material.
2 lemons, grate the peels and retain the pulp
2 cloves crushed garlic
1- to 2-inch piece ginger root, peeled
3 cups maple syrup
1½ cups cider vinegar
2 teaspoons salt
Place all the ingredients in a large saucepan on the stovetop. Turn the heat to high. Bring to a boil, while stirring constantly. Continue boiling and stirring (this may take some time. If you have a helper, take turns stirring) until the mixture thickens.
Remove the ginger root and pour the chutney into sterilized canning jars. Seal with new tops and screw lids down tightly. The heat from the mixture suffices to seal the top. Allow the chutney to sit on a dark shelf for six weeks before using.
Send questions/comments to the editors.
