Is Japanese Knotweed Edible: Tips For Eating Japanese Knotweed Plants

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By: Mary H. Dyer, Credentialed Garden Writer

Japaneseknotweed has a reputation as an aggressive, noxious weed, and it’swell-deserved because it can grow 3 feet (1 m.) every month, sending roots up to10 feet (3 m.) into the earth. However, this plant isn’t all bad becausecertain parts of it are edible. Let’s learn more about eating Japaneseknotweed.

About Eating Japanese Knotweed

If you’ve ever wondered, “is Japanese knotweed edible,” thenyou’re not alone. There are actually a number of “weeds” that can be useful inthis way. The stems of Japanese knotweed have a tart, citrusy flavor, much akinto rhubarb.Better yet, it is a rich source of minerals, including potassium, phosphorus,zinc and manganese, as well as vitamins A and C.

Before you gather an armload of Japanese knotweed, however, it’simportant to know that only certain parts are safe to eat, and only duringcertain parts of the year. It’s best to gather shoots when they’re tender inearly spring, generally under about 10 inches (25 cm.) or less. If you wait toolong, the stems will be hard and woody.

You may be able to use the shoots a little later in theseason, but you’ll need to peel them first to remove the tough outer layer.

Note of caution:Because it is considered a noxious weed, Japanese knotweed is often sprayedwith toxic chemicals. Before you harvest, be sure the plant hasn’t been treatedwith herbicides. Also, avoid eating the plant raw, as it can cause skinirritation in certain people – cooking Japanese knotweed is a better option. Harvestthe plant carefully. Remember, it’s highly invasive.

How to Cook Japanese Knotweed

So how can you eat Japanese knotweed? Basically, you can useJapanese knotweed any way you would use rhubarb and the shoots areinterchangeable in recipes for rhubarb. If you have a favored recipe forrhubarb pie or sauce, try substituting Japanese knotweed.

You can also incorporate Japanese knotweed into jams,purees, wines, soups and ice cream, to name just a few. You can also combineJapanese knotweed with other fruit such as apples or strawberries, whichcomplements the tart flavor.

Disclaimer:The contents of this article is for educational and gardening purposes only.Before using or ingesting ANY herb or plant for medicinal purposes orotherwise, please consult a physician, medical herbalist or other suitableprofessional for advice.

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This herbaceous perennial is a member of the buckwheat family. It was brought over to Europe from Asia as a fashionable ornamental plant in the 1800s’ and then quickly took hold. Thus its “knotty but nice” rep.

Everyone from agriculturalists to amateur gardeners abhors Japanese knotweed because its rhizomes forage the soil for moisture with little regard for anything that stands in its path. It’s notorious for its cunning manoeuvres, speed and ability to mine nutrients from other (native) plants. Yes, this bully of buckwheat will overcrowd any space and overpower any competition in the blink of an eye.

If you’re looking to buy property, and you spot Japanese knotweed in the yard, look no further —it’s even been known to tear into buildings’ facades! In fact, the International Union for Conservation of Nature even lists it as one of the world’s worst invasive species . ‘Nough said.

The plant that’s eating B.C.

Japanese knotweed is in nearly all our provinces. And the threat is real: it can lower house prices, threaten our bridges, and drive men to madness.

Photo illustration by Levi Nicholson and Richard Redditt

It was June of 2013, and, by then, Joe Cindrich knew plenty about the enemy massing for an invasion of his two-hectare hobby farm in Langley Township in British Columbia’s Fraser Valley. He’d been all over the Internet. “I just researched the hell out of it,” he says. He knew his fears were justified, and he set off for a township council meeting to raise the alarm. He carried with him the root of the problem: fragments of Japanese knotweed, a demon weed so relentless, bloody-minded and destructive, it’s been called the terrorist of the plant kingdom. It spreads like a cancer, rips through faults in asphalt and concrete, is as resistant to attack as a colony of cockroaches. “If it’s not eradicated, it will spread,” he told them. “It’s horrible.” He warned of legal liabilities. He recalls them looking skeptically at this white-haired, retired gentleman farmer with his bag of plant cuttings. “They couldn’t believe it,” he says. “Then, a few of them councillors got on their their phones and looked it up and said, ‘Holy God, you’re right!’ ”

Councillors ordered a staff report, and Cindrich returned to his lonely war against a dense thicket of knotweed that had grown to 1,800 sq. m and clearly had territorial ambitions. It was on a neighbouring property belonging to a widow. “She thought it was beautiful bamboo,” though she had no idea how it had gotten there. By now, Cindrich had revised his tactics. A frontal assault with pick and shovel only seemed to make it grow faster. He opted for chemical warfare, settling on a 12- to 15 per cent solution of the herbicide Roundup injected into each individual stalk: maybe 10 seconds per stalk stalks by the tens of thousands hours by the hundreds. He was a one-man conscript in a war of attrition. He’d be out most mornings, mixing his chemicals, wielding his injection machine, as relentless as a knotweed. It is the hobby from hell. “But,” he says, “what is the alternative?”

The alternative, in fact, is chaos. It has crept on cat’s feet into all provinces with the likely exceptions—so far—of Manitoba and Saskatchewan, says Gail Wallin, executive director of the Invasive Species Council of B.C., and co-chair of the Canadian Council on Invasive Species. The spread is helped, some studies suggest, by climate changes that have extended its range. It is changing river flows, choking spawning beds, undermining riverbanks, shorelines and hillsides, punching through roadways and threatening the foundations of homes.

How scary is this plant? When engineers found it growing beside the massive concrete footings of Vancouver’s Lions Gate and Ironworkers Memorial Second Narrows bridges, it was deemed a safety threat requiring lethal chemical intervention. “The ministry of transportation takes knotweed extremely seriously,” says Jennifer Grenz, program manager for the Invasive Species Council of Metro Vancouver. “They are very aggressive in their treatments, because of the threats to infrastructure. We’ve had examples of plants we’re pretty sure have gone under four lanes of highway and have popped up on the other side.”

When a huge infestation of Japanese knotweed was discovered at the coastal Mission Point Park in the Sunshine Coast community of Davis Bay, B.C., crews from the District of Sechelt attempted a chemical-free strategy. They moved in with an excavator and dug out the plants to a depth of about three metres. The next year, parks supervisor Perry Schmidt would later report, the knotweed doubled in size.

The threat level is so high that Wallin and her national co-chair, Barry Gibbs, are pushing to relax varying provincial limits on using herbicides close to waterways. In B.C., for example, herbicide use is prohibited within one metre of a shore, creating “havens” of knotweed, says Gibbs, executive director of the Alberta Invasive Species Council. Mechanical means such as digging and pulling risk sending plant fragments adrift to colonize elsewhere. “When you’re thinking of using a herbicide like glyphosate [usually sold as Roundup], you have to look at the risk of not doing it,” says Gibbs. There is a need to hit the weed hard, with early identification of infestations, tougher regulations, and chemistry, “before it’s like the U.K., where it’s essentially an epidemic,” says Gibbs.

Britain does indeed have it worst. A single stalk of knotweed found on a property, or even on a neighbour’s lot, devastates a house’s value and makes it near impossible to obtain a mortgage or insurance. It has led to financial ruin, depression, even a murder-suicide. A botched attempt to remove the weed may only drive it underground, where it can remain dormant for a decade or more. “Once the coast is clear, once you’ve built your nice, new conservatory, up it pops again,” notes a Sunday Times magazine cover story, “The plant that ate Britain.” The article continues: “The trick is to poison it slowly, subtly, so it won’t notice, like an Agatha Christie nun slipping drops of arsenic into the vicar’s nightly bowl of soup. The process can take up to five years.”

A knotweed plant arrived in England in 1850 and was added to the collection at the Royal Botanic Gardens at Kew on the fringes of London. It was a specimen from a plant, plucked by European adventurer Philipp von Siebold some years earlier, from the rugged slopes of a Japanese volcano and transported to Holland. It became a darling of U.K. gardeners and landscapers (and, later, those in Canada), who loved its tall, dense stands of bamboo-like stalks, its lush leaves, white flowers and ease of growth. Growing was never the problem. The slightest fragment of root or stalk dropped on disturbed ground will colonize. It advances as much as eight centimetres a day, and can reach five metres in height or more. It is hardy. Subsurface, its roots can extend three metres or more deep, and 20 m across, in a constant search for water and the tiniest cracks or seams in barriers blocking its quest for light. Just over a century and a half after the plant arrived in Kew, there is not a single 1,500-ha patch of ground in the entire U.K. that is not rooted with at least one Japanese knotweed, all perfect DNA clones of von Siebold’s disastrous legacy.

The U.K. government estimates that the cost of controlling knotweed has hit the equivalent of $3 billion. In just one epic example, organizers for London’s 2012 Olympic Games had to eliminate a knotweed infestation on a patch of east London land on the proposed site of the velodrome and aquatic centre. In some areas, rendering it safe required a three-year herbicide assault on the plants. Where construction schedules required a faster solution, the plants were rooted out by deep excavation and dosed with herbicide, then roots and stalks were screened from the dirt and incinerated. Knotweed-contaminated soil was then buried to a depth of five metres, after it was encased in a “proprietary knotweed root membrane.” A further two metres of clean fill was added on top, carefully sorted of sharp objects that might cause a tear and allow a knotweed shoot to arise from its sarcophagus. Vampires don’t merit that much respect. Total cost: the equivalent of about $130 million.

But it is Brits without deep pockets who have it worst. An estimated 220,000 homes are infested, fertile ground for a lucrative new branch of the legal industry. Reports abound of it ripping through foundations, infesting floor and wall cavities and poking out of baseboards and electrical sockets. A single stalk in a back garden killed a house sale for a woman called Mary, the Sunday Times reported. The culprit, a neighbouring care home, had to spend about $35,000 to remove the plant after it was threatened with a lawsuit. Mary eventually found a buyer, but at a substantial loss. Another homeowner, Sarah, was in a legal battle with a neighbour, who refused to remove the weed from her own garden. Because Sarah’s property was under siege, her lender was threatening to cancel her mortgage. Perhaps the saddest case, though one obviously clouded by mental illness, was triggered by the discovery (mistaken, it would later turn out) of knotweed in the garden of Kenneth McRae. “I believe I was not an evil man,” he wrote, “until the balance of my mind was disturbed by the fact that there is a patch of Japanese knotweed, which has been growing over our boundary fence on the Rowley Regis golf course.” The note was read at a coroner’s inquest after he battered his wife to death with a perfume bottle before killing himself.

Awareness of the potential problem in Canada has dawned more slowly. In the U.K., those caught selling or dumping knotweed are subject to fines, or up to two years in jail. In Canada, it is only in recent years that most knowledgeable garden centres have stopped selling knotweed. Even now, knotweed sometimes slips into inventories of weekend plant swaps, or even big-box garden centres, where it is sold as “false bamboo,” says Wallin. Adding to its falsely benign image is the fact that spring shoots of knotweed are edible, sort of a cross between asparagus and rhubarb. Internet recipes abound for things such as strawberry knotweed pie, knotweed muffins, even knotweed wine. Don’t go there, says Wallin.

In Vancouver, crews have just finished treating outbreaks of knotweed throughout Stanley Park. They wisely posted explanatory signs telling why the infestation merits the exceptional use of herbicides in the iconic site. Even so, spray crews are sometimes castigated by those objecting to herbicide use, says Grenz of the Vancouver invasive-species council. “We’re an environmental non-profit . . . and we don’t take it lightly. We’re being accused of all kinds of things: that we work for chemical companies and we have some other kind of agenda. But we’ve seen first-hand what it does,” she says of the weed. “We’re trying to use these tools to stop major catastrophes with infrastructure, to keep people safe and allow there to be salmon habitat.”

There have been many successes. “We’ve been at this for a solid five growing seasons, and can comfortably say we’ve eradicated it from a number of areas,” says Grenz. “Without having to do any restoration work, we’re seeing the native species return on their own.”

Unfortunately, that progress comes with a caveat. Rather like the marauding killer plants in the sci-fi classic Day of the Triffids, knotweed is not the surrendering type. In Canada, especially B.C., a mutant hybrid has developed, a cross between Japanese and giant knotweed known as Bohemian knotweed, which now accounts for about 80 per cent of infestations, by one estimate. “The monster we thought we had, which is what happened in the U.K., is turning out to be our own sort of unique monster,” says Grenz, “presenting even more issues.”

Whereas Japanese and giant knotweed spread only by root and stem fragments, and usually at predictable rates, Bohemian knotweed is a runaway train. “All of a sudden, we were noticing that knotweed was popping up everywhere. You’d look at one patch one year and then, next year, it’s more than doubled and we were trying to figure out what was going on,” says Grenz, who is doing graduate work on the hybrid at the University of British Columbia. “It was ending up in really bizarre locations, where it wasn’t possible for anyone to have moved any. What we discovered is that the seeds are actually quite viable, and they’re prolific seed producers. On one branch, you’re looking at 100,000 seeds.”

With that come a host of questions. How long are seeds viable in the soil? Can birds spread them? Will the genetic variability that results from seed production, as opposed to the cloned reproduction of Japanese knotweed, eventually result in a herbicide-resistant strain? Grenz asks. “It just puts a new urgency on us to quickly, swiftly be dealing with this, or forever be chasing our tails and losing valuable habitat.”

When Joe Cindrich drives the highways and back roads of the Fraser Valley these days, he sees much evidence of spray and injection attacks on his old foe. He’d like to think he helped to raise the alarm. His neighbour’s crop is now largely obliterated. A few new plants pop up, but Cindrich never lets them get beyond a foot high before he doses them with extreme prejudice.

Meantime, in the U.K., and now, B.C., combatants are testing a new weapon in their slim arsenal. It’s a tiny sap-sucking bug called a psyllid, a Japanese predator that appears to feed exclusively on knotweed. The bugs have been introduced under strict controls to several sites in the U.K. There are also a few psyllid trial sites in B.C., Wallin confirms. That said, don’t expect Canada to be importing an army of the “little critters” any time soon, she says. “There is a lot of science that goes into it before it is determined if the biocontrol is a safe one for use in B.C. and in Canada.”

No one wants to be remembered as the next von Siebold, the one who introduces a promising new species, with catastrophic results.

I have read that you can serve knotweed like a vegetable, simply steam it. However, it does taste like rhubarb with a texture like asparagus. It is certainly interesting and I think I will need to experiment with it further before I can really suggest that it works.

As knotweed is such an invasive plant you have to be aware that it can be regually sprayed. The patch that I found is in an area that I walk past every day and so I know that it is safe. If you have any doubt about your patch of knotweed being sprayed then I would strongly advise on leaving it well alone, it is simply not worth the risk. I have seen a patch that has been sprayed for knotweed and 3 years on it is still fairly barren.

A second note of warning is about the crop once you have picked it. Do only use the first shoots of the year (15-20cm or 6-9 inches) as the adult plants are not only too tough to eat but they have a sap inside them that can leave your mouth blistered.

Whenever we contduct our wild food walks we always tell people to only pick what they will eat and leave at least a 2 thirds of the plant or if there is only one plant in one area then leave it alone. Japaneses knotweed is slightly different in that (I personally think) you are doing a bit of service by harvesting it as it must weaken the plant. So take as much as you use and even cook it up and freeze it. Although do use all of it, I have heard of people throwing bits away only to find it growing out of the bin. So I would advise burning anything that you have left over or at least try cooking and eating all of it.

Remember that the plant can grow from a piece of the root the size of your thumbnail so it is rightfully covered by the Environmental protcetion act (see below).

Environmental Protection Act 1990 Japanese Knotweed is classed as ‘controlled waste’ and as such must be disposed of safely at a licensed landfill site according to the Environmental Protection Act (Duty of Care) Regulations 1991. Soil containing rhizome material can be regarded as contaminated and, if taken off a site, must be disposed of at a suitably licensed landfill site and buried to a depth of at least 5 m.

An offence under the Wildlife and Countryside Act can result in a criminal prosecution. An infringement under the Environmental Protection Act can result in enforcement action being taken by the Environment Agency which can result in an unlimited fine. You can also be held liable for costs incurred from the spread of Knotweed into adjacent properties and for the disposal of infested soil off site during development which later leads to the spread of Knotweed onto another site.

The stems grow up to 10 ft in height, are hollow, and have nodules every so many inches, resembling bamboo.

The flowers are a small, cream or white, produced in erect racemes a3-6 inches long in late summer early autumn.

It was brought to Europe and the US as a decorative landscaping element.

Other names include fleeceflower, Himalayan fleece vine, monkeyweed, monkey fungus, Hancock’s curse, elephant ears, pea shooters, donkey rhubarb, sally rhubarb, Japanese bamboo, American bamboo, and Mexican bamboo (although it is neither a rhubarb or bamboo).

In chinese medicine it is known as Huzhang which translates to tiger stick.

If you want to learn more about foraging wild edibles and medicinals, you HAVE to check out Herbal Academy’s Botany and Wildcrafting course! It’ll teach you how to identify plants properly, ethical foraging practices and how to use what you forage in homemade medicines!

It is listed as one of the world’s worst invasive species. The root system is large and strong enough to break through concrete sidewalks or foundations.

You’ll frequently see it on roadsides, construction sites, or any place the ground has been turned up.

It will grow in such a dense colony that it will crowd out any other plant. It is so prolific, any part of the plant can grow new roots, so be very cautious when harvesting this plant to not drop any part of the plant on your way home.

I would not recommend putting this in your compost bin. In fact, in the UK, landfills have to be licensed to handle Japanese Knotweed.

Uses For Japanese Knotweed

Japanese Knotweed is highly valued by beekeepers, as the flowers provide a source of nectar when little else is flowering.

For eating the stalks, harvest the young shoots under 10 inches in height. They can be steamed directly as with other vegetables, simmered in soups, or baked in dessert dishes.

For eating the leaves, the Cherokee used to harvest and cook them before eating.


Japanese Knotweed is an excellent source of vitamin A, vitamin C, and the antioxidant flavonoid rutin.

It also provides potassium, phosphorus, zinc and manganese.

It also contains the same resveratrol in red wine that lowers bad cholesterol, but in higher quantities! In fact, it has the highest concentration of resveratrol of any known plant.

Medicinal Uses of Japanese Knotweed

There are over 67 compounds in Japanese Knotweed that have been identified for medicinal properties, including stilbenes, quinones, flavonoids, emodin and polydatin.

Emodin has been shown to be effective against MRSA by destroying the bacteria’s cell wall and cell membrane in vitro.

Eating large quantities of Japanese Knotweed will act as a gentle laxative, like rhubarb.

It is also said to be very effective when used to treat and prevent Lyme’s disease. It does this by addressing the infectious aspects of Lyme disease with its antibacterial and antispirochetal properties, but also addresses the symptoms through immunomodulatory and anti-inflammatory properties.

Resveratrol has been shown to cross the blood-brain barrier and can act therapeutically on the central nervous system (CNS) for those cases of Lyme’s that have also crossed. It also inhibits the cytokine cascade, which is one of the more disastrous effects of Lyme’s in the CNS.

It contains anti-inflammatory properties that make it effective against rheumatic pain.

In addition to it’s potent anti-inflammatory and antioxidant properties, Japanese knotweed has a number of other mechanisms that may help protect against cancer – by normalizing cell differentiation, inhibiting metastasis, and inducing apopotosis. It can also restrict the formation of blood vessels in the case of tumors and malignancy.

In Traditional Chinese Medicine, hu zhang is used to invigorate the chi and clear heat, to remove toxins and ease pain.

Traditionally, it was used to help balance hormones in women going through menopause. Modern research now backs this up with evidence that it is a mild phytoestrogen which make make it effective in treating hot flashes.

Controlling the Spread

To eradicate Japanese Knotweed on your own property with herbacides, you have to dig up every inch of roots, which can grow up to 10 ft deep. I recommend digging up at least 11 ft around the plant and roots, and burning the soil.

Watch the video: Let it Grow - Japanese Knotweed Timelapse

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