Thursday, May 2, 2013

If You Can't Beat It, Eat It: Japanese Knotweed

By Christina Georgiou

Recently, there's been a lot of attention in Easton being given to the idea of urban gardening, particularly to grow healthier food, and also to the environmental detriments of invasive plant species in the local area.

The idea that the city is a "food desert" has also been floated around a bit, though technically there is no neighborhood that strictly qualifies as one. (To be considered a true "food desert" there needs to be a lack of a dedicated grocery store in a two-mile radius. While it's true three out of four of Easton's neighborhoods don't have a supermarket and it would be a much better thing if they did, all four neighborhoods are within the two-mile reach of one.)

While we are definitely supportive of urban gardening and growing food, favor native plants over invasive ones, and would very much like to see more healthy (and more affordable) foods sold in neighborhood stores, there's one idea that we think is a bit neglected--what already is available and what to do with it.

This is the second article in the series "If You Can't Beat It, Eat It", where we're highlighting a few edible, healthy plants you may not have noticed  (or just call "weeds") that grow all around the Easton area.

Click here to read the first article in the series, on dandelions.

One of many leafy platoons of an army of Japanese knotweed
that is quietly and voraciously taking over plant habitats
in the local Easton area. This one has set up camp along
the Bushkill Creek, crowding out many other native plants.
When it comes to invasive plants, it could be easily said that Japanese knotweed is one of the worst, if not the worst, and few that have ever met this voracious plant would disagree.

Once it gets the tiniest foothold, it takes over like a leafy invading army, creating a "mono-culture" in its immediate environment. Its underground rhizome network sends up fast-growing shoots, which reach heights of three to 12 feet in a matter of a couple of months. During its peak growing time, it can grow one to three inches a day, and when it reaches full height, it's leaves are the size of a man's hand, depriving potential competitors of sunlight.

It's incredibly difficult to kill--a tiny live piece of stem or root in soil with a little water is enough for the plant to regenerate itself. Chemical herbicides aren't terribly effective, and repeated applications of poison over a succession of years are usually necessary to eradicate it.

Other techniques include repeatedly chopping the plant down and removing the vegetation to prevent it from rooting and continuing to spread, as well as burning it. (One suspects the use of a flamethrower might be most satisfying, if not actually prudent.)

Shoots of Japanese knotweed, being a literal "pain in the
asphalt" along Pearl Street in Easton.
Knotweed rhizomes can go 10 feet deep and stretch up to 30 feet away from visible plants. Its roots can--and do--break through concrete and pavement to spread, often causing costly damage to structures and roadways, though it prefers to take hold in disturbed soil, particularly along waterways, which, when their banks flood, is one of the main ways it travels.

It's literally a "pain in the asphalt" to pretty much anyone who has to deal with its unwanted presence.

Japanese knotweed and it's close cousin, giant Japanese knotweed, was imported from Asia in the late 1800s as an ornamental plant. It's droopy flowers, seen in late summer, produce winged seeds, which is another way it establishes itself in new areas.

Areas in the northeast of the U.S. have had a particular problem with Japanese knotweed, but it's found all over the North American continent, including in Alaska. It's also a problem in the UK, Australia and New Zealand. The World Conservation Union has listed it as one of the world’s worst invasive species. Probably the only place it's not considered a major pest is in Japan, where it comes from.

Yes, that's ALL Japanese knotweed. We suspect it's
plotting the demise of that tree on the upper left as
its next conquest.
Locally, Japanese knotweed has become a particular problem along Easton's waterways, said  David Hopkins, the city's public works director.

"It's horrible," he said when I asked him about Japanese knotweed.

He said he thinks flooding is to blame for it becoming especially prolific in recent years. It's crowding out native plants, blocking access to waterways and also harbors ticks in season, he added.

But there is one upside to Japanese knotweed. It's edible, and it's surprisingly tasty and nutritious too.

As a food, it can be used as a replacement for rhubarb in any recipe that call for it, including pies, crumbles, muffins, tarts, sauces, syrups, etc. It can also be steamed or grilled like asparagus. Tea, wine, cordials, and pickles are also possibilities.

Flavorwise, it's unique, with a lemony hint, and somewhat reminiscent of both rhubarb and asparagus, though which it is more similar to seems to depend on its preparation.

While most probably haven't heard of eating Japanese knotweed, the practice isn't rare. Several locations in New England have festivals and/or cooking contests annually centered around Japanese knotweed, and in England, where the plant has also become a big problem, chefs have been developing gourmet recipes to find ways to consume it.

Young Japanese knotweed setting up camp in a field setting.
See those pretty violets on the lower right?
If the knotweed isn't stopped, they're doomed.
Hopkins said he thinks the idea of people eating the local Japanese knotweed is a wonderful idea, and said that foraging the plant for food is perfectly fine in the city.

"I would welcome it if (people) took it all," he said, adding he'd be willing to try some himself. "It would make me feel good to consume something that's been such a pest. What a great thing it would be if people ate it."

Foragers need to be mindful about where they pick from, so as not to pull plants from areas where it is prohibited, as well as making sure their chosen locations haven't been treated with pesticides and herbicides, which is a common way many places deal with Japanese knotweed infestations, but in Easton, this is unlikely to be much of a problem.

The City of Easton has no future plans to apply herbicide in most areas, after it controversially did so along the Delaware River banks in Riverside Park last year, Hopkins said. Any place herbicide is applied on city property will be clearly marked, he added.

In Hugh Moore park, the city will utilize goats starting in June to try to help control runaway Japanese knotweed growth, Hopkins said. The initiative, along with others the city will be trying this year, will be led by the city council's Environmental Advisory Committee. Public works employees will also be chopping down the plant with mowers and weed wackers repeatedly, too.

"We're going to try to not use chemicals at all," Hopkins said.

So, upon discovering that Japanese knotweed is edible, not to mention readily available all over the place, I decided to give it a try.

I have to admit, I wasn't expecting much. I was more expecting that Japanese knotweed is "edible" in an "it will keep you from starving to death at the end of the world" sort of way. I mean, how good could such a horrid plant, and one that grows as tall as a small building and is advancing like a malicious army be?

Japanese knotweed, cooking with butter and garlic. It
not only looks a bit like asparagus, it tastes a lot like
it too.
 Surprisingly good actually. Pan sauteed with a little butter and garlic, it is very much like asparagus with lemon, which I happen to adore.

While there are a number of specific recipes for knotweed crumble out there, I decided to test the theory that it can be substituted for rhubarb in any rhubarb recipe.

Wow, it really does make a very tasty dessert too. The crumble I made has a sour apple taste, and the green color to match, though from a visual standpoint, it looks more like green rhubarb.

The season to harvest Japanese knotweed for food began about two weeks ago, and will continue for a few more weeks, into June, depending on growing conditions and the weather.

New shoots of the plant are reportedly the best, though the top 6 to 12 inches of taller plants are also fine. Basically what you're looking for is the tender parts, before the mature plant becomes woody and too stringy to be tasty.

Harvesting Japanese knotweed is a snap, literally. You can just break off the hollow stalks, or snip it with scissors, if you prefer. Anywhere where the stalk is too tough and stringy to do that easily is probably too mature to provide good eating, though I suspect peeled, the stringier stuff would be fine for wine-making and tea.

You can use a basket to carry it home, or just stuff a plastic grocery bag full. (I used two, doubled up. En masse, the vegetation gets a little weighty, and I didn't want the bag to split.)

Err on the side of harvesting too much over too little--you're doing the local environment a favor by carrying this stuff off, and there is NO danger of overharvesting here. Once you've tried it too, you may well want to eat more or try other recipes with it, and having it already on hand is easier than having to go pick more.

When you get home, to prepare the knotweed for use, strip it of all its leaves, and chop the top off too. Give it a good rinsing.

If you're not going to use it right away, you can store it in the fridge for a few days as is, with or without the leaves. It will wilt a bit, but the stalks, which is the part you're going to use, should be fine. You can also put it upright in water to keep it crisper, though you definitely don't want to do it for so long that it roots.

As tempting as it may be to compost, this is one plant you definitely should NOT do that with, or you will end up with it growing on your property, out of your compost pile or bin, only furthering the local Japanese knotweed problem. Dispose of unused bits in the regular trash. Or you might burn the scraps on the barbeque and toss the ash in the compost heap, giving it a nice nitrogen boost, if you really want to be a purist about not contributing to landfills while not contributing to the spread of this pest plant.

Many foraging guides I've seen recommend peeling off the skin, though I found that's unnecessary with the youngest stalks. Still, it's a simple process if you need to do it. A light scrape with a knife or using a vegetable peeler is quite effective. The best stalks I harvested ranged in size from 1/4 inch to about 1 inch in diameter, though some smaller stalks were tough and some larger ones quite tender.

To cook knotweed like asparagus, I cut the cleaned young, tender (unpeeled) stalks into 4-6 inch long pieces, and chopped up a couple of cloves of garlic. In a heavy frying pan on a medium heat, I melted about two tablespoons of butter, and tossed the garlic in. After a couple of minutes, I added the Japanese knotweed on top, and while it was pan grilling, I sprinkled a little bit of coarse kosher salt and a dash of black pepper on top. A very  few minutes later, when the stalks had turned a light shade of olive green and went limp, I tossed the entire thing into a bowl.

This turned out to be amazingly good, as I mentioned earlier. The garlic carmelized a bit, and added a nice crunch to the lemony flavor of the knotweed, which softens up considerably when it's cooked. (The stalks should be limp when cooked through, otherwise they'll be stringy and unpleasantly tough. But the limpness is not a detriment to flavor in this case, and the texture is actually still good this way.)

I suspect onions would also be very good with knotweed. Grilling the stuff on a barbeque  in a pan with a little water and then maybe some butter at the end, would also probably work well, either by itself or with other veggies.

Moving on to knotweed's sweeter side, I decided to make a crumble, aiming for something that would serve as a dessert, as well as perhaps a breakfast treat.

Here's the recipe I used for Japanese knotweed crumble, which I adapted from one for rhubarb:

Crumbly-topped Japanese Knotweed
Yes, it was good. Yep, it's all gone now.

Crumbly-topped Rhubarb Japanese Knotweed

  • 3 cups chopped Japanese unpeeled knotweed stalks
  • 1 Tablespoon flour
  • 1/2 cup granulated Sugar
  • 1 teaspoon ground cinnamon
  • 1/8 teaspoon salt
  • 1 Tablespoon water
  • 6 Tablespoons of butter, softened
  • 6 Tablespoons flour
  • 1/2 cup packed brown sugar
  • 1/2 cup rolled oats (regular or quick cooking--either is fine)
Preheat the oven to 350 degrees Fahrenheit.
In a 10x6x3-inch baking dish (that's a standard loaf pan), combine the first six  ingredients. Mix the butter into the flour and brown sugar thoroughly, then stir in the oats.

Sprinkle or spread over the rhubarb. Bake for 40-45 minutes or until the rhubarb is tender and the top is brown.

Again, Japanese knotweed can be used in any recipe that calls for rhubarb. If the recipe says to peel the rhubarb, then peeling the knotweed is advisable. If it calls for unpeeled rhubarb, then peeling the knot weed probably isn't necessary.

If you harvest Japanese knotweed later in the season and it's beginning to get tough, my online foraging sources suggest peeling it down to the more tender core is advisable.

Boiled Japanese knotweed, pre-puree, on its way to
becoming fruit leather.
I chose easy recipes to begin with, having no idea whether Japanese knotweed would be worth the effort.

As it turns out, it most definitely is. Next on my list, besides more "poor reporter's asparagus", is knotweed muffins, knotweed quick pickles, knotweed vodka, and maybe some knotweed wine.

I also found a recipe for knotweed fruit leather that sounds tasty and pretty easy to pull off, which is in the works.

I'm truly amazed at what I found experimenting with Japanese knotweed. I had expected that it would be a lot of work for little gain as a food, and that it might be passable, but not great when it came to tastiness. All of my expectations turned out to be completely wrong. It's pretty awesome stuff.

Give it a shot. It's not only free, nutritious, tasty food, but by cutting it down, you'll be doing your neighborhood and the local environment a big favor!

Finding and identifying Japanese knotweed:
  • It really is everywhere, once you identify it, but known places in Easton and the greater Easton area are along waterways, such as the Bushkill Creek (easily accessible via the Karl Stirner Arts Trail in the city), and along the Delaware and Lehigh river banks. (One place to avoid along the Delaware River though, is in Riverside Park, and also at Scott Park, due to the application of glyphosate last year. Give it another year or two before harvesting from these locations. All other areas along the riverbanks should be okay.)
  • If you see obviously unhealthy or "burned" looking Japanese knotweed, especially surrounded by other sickly looking plants, skip picking from that area. Again, the City of Easton says it doesn't plan to use herbicides this year and will clearly mark areas if they do use chemical means to control plants or pests, but that doesn't preclude private property owners' use of these substances. That said, you may find some old, hollow, long, fibrous stems from last year next to the new shoots. This is actually a good sign that the plant has not been treated. Additionally, waterways, where it likes to grow the most, are protected areas, and should generally be free of such hazards.
  • Japanese knotweed has hollow bamboo-like stalks that are crooked at the "knots" or stem joints. The leaves are large, usually at least a few inches wide, and grow off the stalks  on alternate sides of the stem joints. It doesn't look like anything else that grows in the area, and there are no poisonous look-alikes. Shoots coming out of the ground vaguely resemble asparagus. It usually grows in stands, with many stalks shooting out of the ground in the same area. Due to the fact that it has a habit of taking over anywhere it's becoming established, few if any other kinds of plants will be found growing within the cluster.


  1. Great article! You will have to have me over for crumble (and vodka)!

    1. The vodka may take a little bit. More crumble is in the works though... (The one in the picture was finished off rather quickly, I'm afraid.)

      Glad you liked the piece. Thanks!

    2. The root of Japanese Knotwood is also suppose to have medicinal properties. Check out Invasive Plant Medicine by Timothy Lee Scott.