Last Chance Foods: The Tart Taste of Knotweed Revenge

Friday, May 04, 2012

Japanese knotweed is one of the country’s most pervasive and hated invasive plants. The tender red-freckled shoot may look like an innocuous cross between asparagus and bamboo, but it is so powerful it can push through concrete and asphalt. Urban forager and writer Marie Viljoen called knotweed a “thug” and said that it indiscriminately invades agricultural land and backyards. She exacts her revenge in a visceral and delicious way: Viljoen eats it.

“When it’s really small, up to about 8 inches, it’s at its most tender and most delicious, but it becomes mammoth,” said Viljoen, who recently wrote an article about knotweed for Edible Manhattan

“It can grow to about 5 or 6 feet. It grows inches in a day.”

By late summer, not only is its growth seemingly unstoppable, but the stems become tough and fibrous. When the knotweed is about 3-feet tall, she peels and pickles it, or uses it in soup. 

Knotweed tastes astringent like sorrel and can often be used like rhubarb.

“It has that very tart, lemony flavor,” said Viljoen, who recommends pairing the sour taste of knotweed with other fruit like apples and pears. She also roasts it along with lamb or chicken and has even made a curry from it. 

Viljoen (pictured below doing her best knotweed-inspired impression of "Wildman" Steve Brill in a photo by Vincent Mounier) is relatively careful when foraging for the invasive since toxic herbicides have been created specifically to combat it. She has her own means of determining whether herbicide has been sprayed on a patch of knotweed.

“My entirely unscientific way of assessing the risk factor is to see if there are stems from the previous year’s knotweed,” Viljoen said. “It’s a very distinctive stem. It’s very tall. It’s hollow. It’s dry. So if there are 5-foot stems from the previous year, I’ve decided unscientifically that no herbicide has been applied and I forage away.” Marie Viljoen by Vincent Mounier

While it is illegal to take plants out of New York City parks, Viljoen admitted that she has no qualms about chopping off knotweed shoots wherever she sees them.

“Well, my vigilante justification is that this is a thug,” she said.

Viljoen added that’s she’s careful not to stomp on anything precious and is helping to eradicate a pest that costs the parks department a huge amount of money and person power to control. 

Katerli Bounds, the deputy director of forest restoration for the parks department’s Natural Resources Group, said that the knotweed invasions on public land are treated with a combination of herbicides and mechanical clearing. For smaller swaths, the parks department just digs up the knotweed.

The team needs to be particularly thorough in trying to eliminate all the pieces of knotweed though. Viljoen says that the plant spreads through its rhizomes, or underground stems, so any pieces of stem left behind will just take root and grow new shoots.

“Pulling up knotweed is arguably worse than any other method of controlling it,” she said. 

Instead eating the tender young knotweed shoots may be an effective, herbicide-free means of getting rid of the pesky plant.

“Anecdotal evidence shows that if you keep picking off those very young shoots often enough year after year, the rhizome mass under the ground just gives up,” explained Viljoen. “It has no more carbon reserves and that’s the end of the knotweed.”

That method of ending knotweed may well create the beginnings of many delicious meals at home.

“A weed is really just a cultural way of looking at a plant we don’t want,” pointed out Viljoen.

Rather than considering knotweed as a problem plant, perhaps now is the time to start seeing it as the source of a feast. Try Viljoen’s Knotweed Soup recipe below.

Knotweed Soup

I used quite mature knotweed shoots for this, up to 3-feet tall, but not leafed out yet. The skin for larger stems is tough and must be peeled off, much the way you'd pull strings from rhubarb or celery. This exposes the pale, bright green, crisp and sour knotweed stem. I also discard the joints between segments, considering them too fibrous for the smooth puree that I wanted. When cooked in moist heat knotweed collapses into a lemony creaminess, for which bland potato is a perfect foil. —Marie Viljoen, 66 Square Feet

  • 1 Tbsp butter
  • 1/2 cup finely chopped shallots
  • 4 cups peeled and sliced knotweed
  • 2 small potatoes, peeled and sliced thinly
  • 3 cups chicken stock
  • salt to taste

Heat a saucepan and when the butter in it is foaming, add the shallots. Cook gently till translucent. Add the knotweed and stir, cooking for a couple of minutes until it changes from fresh green to drab khaki (just like sorrel). Add the potato and the hot stock and cook until the potato slices are tender. Allow the soup to cool a little and then puree in batches in a blender. Strain each batch to remove any fibers and return the saucepan to heat. Taste and adjust seasoning if necessary.

Serve hot.

Young Japanese knotweed shoots in front of mature stems from the previous year.
Marie Viljoen
Young Japanese knotweed shoots in front of mature stems from the previous year.
Japanese knotweed in New York City.
Marie Viljoen
Japanese knotweed in New York City.
A close-up of a knotweed shoot.
Marie Viljoen
A close-up of a knotweed shoot.
Young Japanese knotweed.
Marie Viljoen
Young Japanese knotweed.
Gear for a day out foraging.
Marie Viljoen
Gear for a day out foraging.
Bunches of knotweed kept in water.
Marie Viljoen
Bunches of knotweed kept in water.
Japanese knotweed revenge on the cutting board.
Marie Viljoen
Japanese knotweed revenge on the cutting board.
Knotweed prepared for curry.
Marie Viljoen
Knotweed prepared for curry.
Knotweed curry.
Marie Viljoen
Knotweed curry.
More mature knotweed that has been peeled.
Marie Viljoen
More mature knotweed that has been peeled.
The making for quick-pickled knotweed.
Marie Viljoen
The making for quick-pickled knotweed.
Spicy quick-pickled knotweed shoots.
Marie Viljoen
Spicy quick-pickled knotweed shoots.
Knotweed soup.
Marie Viljoen
Knotweed soup.
Knotweed for roasting.
Marie Viljoen
Knotweed for roasting.
Knotweed roasted under chicken with field garlic and potatoes.
Marie Viljoen
Knotweed roasted under chicken with field garlic and potatoes.


Marie Viljoen

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Comments [16]

Very interesting article. I'm intrigued by the savory use. I posted a link to your post on PlantForagers:

Sam Schaperow, M.S. (Co-Moderator) (Co-Director)

Apr. 19 2013 11:25 AM
Debbie from Metro-Detroit, MI

The land has belonged to humans before there were organized cities/states. Foliage is put on the earth to replenish man and beast. "Weeds" as my horticulture teacher would say, "are anything that you do not want (and can't control)." There are multitudes of weeds...likely more than plants/flowers. Consider this: food source, medicine, etc. They are here for a reason. Use them!!! Modern mankind is so stupid because they do not have the same sense as animals to determine if something is edible/poisonous. Matters like this used to be common knowledge. Now that man is "so educated"--what are we smart in? We can't do anything without our computers? Remember when the power grid went out in 2002? It shut down several states for days. Even water pressure was lost. Just suppose (and I know this is a stretch for some of you)that the power and water was incapacitated for several months. How would you survive? --esp. those who live in the cities away from "land". Where would you get your water from? Do you know how to prepare it to make it safe? What would you eat when all the marts were looted and nothing was coming or going? What would you do? I'll bet you never thought of it! Here's the answer: most people would die! So keep your lofty self-righteous entitled ideas about bashing foraging and continue to eat food that's processed or not fresh. That's your prerogative! But remember something: everyone has a choice in this world, and ultimately, it is up to them to live to the fullest and survive as well as thrive. I would be mad if someone went on my property and started taking things without asking. But frankly, plants in Central Park while they DO belong to the people, most people barely pay any attention. They have their noses glued to their smart-phones or their tablets! (P.s. I'll bet you don't know WHO designed Central Park...who were the Landscape Architects and supportive plantsmen ..... well I do! --- Frederick Law Olmsted and Warren Manning, and they likely would have been okay with people eating weeds!

Oct. 03 2012 08:24 PM
Anne from Manhattan

Do you do foraging tours? I would like to learn to recognize knotweed next spring. The soup sounds delicious.

Sep. 18 2012 12:13 PM
Lewis Blake from Western NC

Thanks all for your comments, I hope this conversation is constructive for everyone. I would like to add my voice: I am a forager and I steward my environment by participating in it, not by locking it up!

May. 11 2012 06:00 PM
Eric from El Paso

Why would you attack foraging? What is wrong with learning about wild plants? Do you insist we are all ignorant and stupid like you? ...all aliens in our environment?

Yes, we should all trust the CARING grocery store and the OH SO RELIABLE ELECTRICITY (Carrington event).

I can't believe you attacked foraging; go burn some books, loser.

May. 08 2012 10:20 PM
Abe from Bellingham, WA

Foraging in parks is often NOT Illegal. While I don't live in New York, I put together a list of all the major public land managers in the Pacific Northwest, including several National and State Parks. More than half of them allow foraging in one form or another. (Google "rule for foraging on public lands" or See

Abe Lloyd, MSc
Wild Harvests

May. 08 2012 12:04 AM
Kathryn Marsh

I can't believe that someone could say that removing Japanese knotweed from a park is self-indulgent and destructive. In fact I'd reckon that spotting JK growing in a park and leaving it there is destructive of public property. The stuff is a complete nightmare. And digging as a method of removing it, unless you are putting the soil through a fine sieve, is more of a method of propagation than anything else.

May. 07 2012 04:09 PM
Leda Meredith from Brooklyn, NY

As I have done before, I invite any Parks Dept. personnel to come on any of my foraging tours in the NYC parks. I would love for you to hear how I educate people about sustainability issues including the issue of slow-growing native species vs. invasive non-native species (that Parks itself brings in volunteers to weed out). I am on Parks' side as far as wanting to perpetuate sustainable plant populations and environments in the parks. I believe that the key to that is more, not less, education.

May. 07 2012 04:00 PM
Ellen from Manhattan

I'm glad to see that most listeners understand that foraging for knotweed is a public service, rather than a misdemeanor. And I love KD's suggestion for a sustainable foods partnership between foragers and the Parks department! Just imagine Japanese knotweed soup or garlic mustard pesto being served in soup kitchens across the city. Now THAT's a win-win situation.

May. 07 2012 03:56 PM
Pascal from Los Angeles

Here in Southern California, most of the "weeds" we eat are non-native and invasive. Plants such as mustard,fennel,various thistles, curly dock, black mustard and so many more! Sometimes I think the public park services should pay foragers for their valuable service and contributions.

May. 07 2012 03:52 PM
"Wildman" Steve Brill from mamaroneck

Foraging is neither self-indulgent nor destructive. Anyone who has the slightest knowledge of ecology recognizes the difference between renewable and non-renewable resources. When you pick dandelions, Japanese knotweed, garlic mustard, field garlic, chickweed, dozens of other healthful, delicious wild greens where they're abundant, and take a fraction of what you see (which is what all the thousands of foragers I know do), they simply regenerate.

And the smallest amount of common sense will tell you that harvesting black walnuts, white oak acorns, mulberries, wineberries, crab apples, or dozens of other wild fruits and berries doesn't cause the trees or bushes fall over dead (and there's zero impact on wildlife during the plentiful foraging season, as it's during the winter that animals have difficulty finding food!)

If foraging is so destructive, why did the NYC Parks Dept. pay me to lead foraging tours every Sat., Sun., and holiday, March to December, from 1986 to 1990? Why did Parks Commissioner Adrian Benepe (who was the head of my unit, The Natural Resources Group, back then) invite me to his office on August 12, 1994, and tell me that he admired my work?

Foraging is actually very good for the environment. Generations of foragers I taught have become motivated to take better care of our non-renewable resources. The kids I teach become very excited about nature and science through foraging, and this sticks. Some are now science teachers who schedule foraging tours with me for their classes!

I've been leading foraging tours for over 30 years, visiting the same spots with large groups throughout Greater NY and the NE. Not one species has lessened as a result, and mowers still come to cut down the edible "weeds."

The Parks Department's real motive for opposing foraging, as Commissioner Benepe told me to my face, was fear of frivolous lawsuits: if foraging were allowed, someone could fake getting poisoned and sue the city! That's why my undercover agents infiltrated my foraging tour of March 29, 1986 and handcuffed and arrested me for eating a dandelion in Central Park, before Parks Dept. officials negotiated with me, dropped the charges, and hired me, to escape scathing ridicule of the national media.

I'm extremely disappointed by Parks Department officials' regression to their pre-1986 stance, yet again wasting taxpayer money to indulge their groundless paranoia, and covering this up with a shameful campaign of misinformation. Congratulations to WNYC for understanding the wonders of foraging, and for not being taken in by self-serving and overbearing bureaucrats who have nothing better to do with taxpayer money than to misuse their power.

May. 07 2012 03:15 PM
KD Jeffries from Brooklyn,NY

Indeed, having done an internship with the Parks Department it is unbelievable how many resources are dedicated to getting rid of "invasive species". There are many people who forage in the parks for edible foods while crews of people are destroying these plants,gathering them into garbage bags and hauling them to garbage trucks. This is a shameful waste.
I never understood why the Parks Department never developed a sustainable foods partnership with the many organizations that exist to develop an income stream by harvesting these plants. Maybe the law against foraging certain species needs to be revised.
We need to Love the knotweed not hate it!

May. 05 2012 11:40 AM
MI Marker from NY NY

Anyone who is plucking knotweed, whatever the motive, is doing a public service. Following the law regarding foraging is all well and good, but the law has to be tempered with an ounce of good sense. Knotweed is an insidious, unstoppable invader. Pluck away. There will never be a shortage.

May. 04 2012 10:27 PM
Marie from Cobble Hill

Louise - Why don't you visit with me one day and I'll show you just how it's done. I think you will be (happily) surprised.

May. 04 2012 07:40 PM
Laura C from Rockland County, NY

I was not in a public park, but listening to WNYC and pulling out of a space in a parking lot when I looked up and saw what I was now sure was Japanese knotweed. I tore off a stalk, took it home - sure enough it was! What a fun discovery, thanks to you. And I'm trying a different recipe for soup, but so thankful for your piece.

May. 04 2012 07:38 PM
Louise Berenson from Near Central and Riverside Parks

Foraging in pjublic parks is ILLEGAL no matter how noble your motives.
It is self-indulgent and destructive. You should not be encouraging it in any way whatsoever.
I am extremely disappointed in you and WNYC.

May. 04 2012 05:55 PM

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Last Chance Foods covers produce that’s about to go out of season, gives you a heads up on what’s still available at the farmers market and tells you how to keep it fresh through the winter.


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