Japanese Knotweed: Foraging And Using It

Easily found in many areas, Japanese knotweed has a slightly tangy flavor that makes it useful in any recipe calling for rhubarb.

In the Spring, Japanese Knotweed comes into season. Also known as Fallopia japonica, it can be identified by simple leaves that alternate and appear to be a broad oval.

Other names for the plant include Reynoutria japonica and Polygonum cuspidatum, along with the common name Asian knotweed.

harvested Japanese knotweed in hand
harvested Japanese knotweed in hand

This native species comes from Eastern Asia, and was first introduced in the early 19th century. It was brought to North America to help with soil erosion, livestock forage, and to be an ornamental plant.

The stems of the knotwood are hollow, and have notches on it that make it appear like bamboo. The reddish-green hues of the leaves are similar to rhubarb.

When it blossoms, the flowers are creamy to white color and will appear in late summer, usually in August or September.

The Japanese knotweed is a large plant that is actually in the buckwheat family. It’s all over in the early spring through fall, and in many places in the United States, it’s considered an invasive species.

It thrives in dense thickets and while beneficial in terms of preventing flooding and erosion control, it deprives nearby plants of other natural resources and can reproduce with tiny root fragments – making it highly invasive. It doesn’t need a complex root system to thrive and spread!

There are some countries that have laws against planting this species due to its ability to rapidly spread and take out other native vegetation. It forms a dense thicket that can wipe out other native perennials in the area, and is thought to harm biodiversity.

Japanese knotweed stems
Japanese knotweed stems

Here’s Why You Shouldn’t Use Herbicide on Japanese Knotweed

Japanese knotweed is an invasive plant species that has been causing problems for homeowners and landscapers for years. It is a significant threat to nearby vegetation.

Although it’s often seen as a nuisance, there are actually a few good reasons why you shouldn’t use herbicide to get rid of it.

For one, Japanese knotweed is an incredibly attractive plant, with its red-tinted leaves and bamboo-like stalks. It’s also a great habitat for birds, small mammals, and lizards. Additionally, the plant is edible and quite delicious.

Finally, Japanese knotweed is actually good for you. It contains high concentrations of resveratrol, the same compound found in red wine that has numerous health benefits.

So next time you see Japanese knotweed on your property, don’t reach for the herbicide. You might be surprised to learn that this “pest” can actually be beneficial.

What Does Japanese Knotweed Taste Like?

Japanese knotweed tastes similar to asparagus or rhubarb. When cooked, it has a slightly sweet flavor with a hint of acidity. The plant’s young shoots are the most commonly eaten part of the plant, but the stems and leaves can also be eaten.

Japanese knotweed can be cooked in many different ways, including boiled, stir-fried, and baked. It can also be used raw in salads or as a garnish.

If you’re curious about Japanese knotweed, why not give it a try? You may be surprised by how delicious it is!

Can You Eat the Leaves?

If you’re lucky enough to find some Japanese knotweed while you are foraging, you might be wondering if you can eat the leaves. Unfortunately, the answer is no – the leaves are quite tough and have a strong taste that many people find unpleasant.

If you do decide to try eating the leaves, cooked or raw, make sure to thoroughly wash them first – they can contain harmful toxins if not properly cleaned.

How to Forage for It

For many wild foods, knowing how to forage for them ethically is paramount to their survival. When you find knotweed, it will be along river banks commonly, as it can grow better due to the movement of water.

Knotweed can spread by seed, or the rhizomes (roots that grow below the ground) and can spread up to 30 feet from the parent plant.

Identifying Japanese Knotweed

Japanese knotweed has thick, hollow stems that are often speckled with purple flecks. The leaves are Heart-shaped and about the size of a human hand. The flowers are small and white, and they grow in clusters along the stem.

Dwarf Japanese Knotweed

There is another variety of Japanese knotweed known as dwarf knotweed.

When foraging for Dwarf Japanese Knotweed, it is important to be able to identify the plant. Dwarf Japanese Knotweed typically has small, dark green leaves and slender, purple-tinged stems. The plant grows in clusters, and the flowers are white or pale pink.

When foraging for Dwarf Japanese Knotweed, look for plants that are growing in shady, moist areas. The plant is often found near streams or rivers.

When harvesting Dwarf Japanese Knotweed, be sure to only take the leaves and stems. The roots of the plant are not typically edible.

How Does Japanese Knotweed Spread?

Japanese knotweed can spread both vegetatively and by seed. The plant produces underground runners, or rhizomes, which can rapidly grow to form dense colonies.

These runners are capable of growing up to 20 feet in a single season and can easily break through concrete and asphalt. Japanese knotweed also produces small seeds that are dispersed by wind and water. Once established, Japanese knotweed is difficult to control.

Where Does Japanese Knotweed Typically Grow?

Anywhere it wants, basically. It can thrive in almost any environment, from river banks, to contaminated soils.

It prefers open sunny areas, but will still be found in shade along river banks. Removing the plant from the root entirely is important.

However, once at home, you do not want to compost the root or seeds. It can survive, thrive and grow easily unless the compost heat is high enough to kill it. A piece of stem as little as 1 cm is all that is needed to grow a new plant and spread.

This wild edible can and will spread like wildfire if great care is not taken. You will also want to be sure not to walk through the area of where it is growing, as that could even cause it to spread.


  • Giant Knotweed (Fallopia sachalinensis)
  • Bohemian Knotweed (Fallopia × bohemica)
  • Himalayan Knotweed (Persicaria wallichii)

Be Mindful of Where You Harvest it From

It is important to be mindful of where you harvest knotweed from. The plant is often treated with pesticides, and eating contaminated knotweed can cause serious health problems.

Avoid Japanese knotweed vegetation growing along roadsides or similar riparian areas. It may have been sprayed with dangerous chemicals like a surfactant or a triclopyr, imazapyr, or glyphosate (roundup) foliar spray.

If you do choose to harvest knotweed, make sure to do so from an area that has not been sprayed with chemicals.

Should I Grow Japanese Knotweed in My Garden?

Japanese knotweed is an incredibly powerful and fast-growing plant. In the wild, it can grow up to three feet in a single growing season!

This makes it a seemingly popular choice for gardeners looking to add a touch of variety to their gardens.

However, Japanese knotweed is also notorious for being incredibly invasive. It is found on many noxious weed lists. Once it takes root, it can quickly crowd out other native plants and cause extensive damage to garden beds.

For this reason, many experts recommend against growing Japanese knotweed in your garden. If you do choose to grow it, be sure to take precautions to prevent it from spreading.

And after foraging for it, be sure to clean your tools afterwards to prevent the spread of this destructive plant.

Don’t Compost It, Either

If you’re planning to harvest Japanese knotweed, it’s important to take precautions to prevent the plant from spreading.

One way to do this is to microwave the pieces after harvest. This will kill the plant and prevent it from taking root in new areas. It’s also important to dispose of the plant properly.

Do not compost the pieces, as this could spread the plant to other parts of your garden. Instead, put the scraps in a sealed bag and throw them away in the trash.

When to Harvest Japanese Knotweed

The best time to harvest Japanese knotweed is when the shoots are less than 50 cm long. The young shoots are less fibrous and easier to peel, making them ideal for cooking. You can also juice the whole stems, in which case it doesn’t matter how old they are.

Japanese knotweed is a versatile plant, and there are many ways to enjoy it. Whether you cook it, juice it, or simply enjoy it raw, make sure to harvest it at the peak of freshness for the best flavor.

Is Japanese Knotweed Safe To Eat?

Yes, you can eat Japanese knotweed. It has a slightly sweet tang like rhubarb to it. Japanese knotweed uses range from being in jellies, jams, pies, and cobblers like rhubarb would be used. You can also make a japanese knotweed root tea or tincture.

There are some health benefits to it, as it’s considered high in resveratrol, a potent antioxidant. This is the same antioxidant that red wine has.

The shoots are used raw or cooked. If eating raw, the young shoots are more desirable as the older shoots can be fibrous. Knotweed is a good source of fiber.

chopped Japanese knotweed
chopped Japanese knotweed

Knotweed Squares Recipe

For the crust:

  • 2 cups flour
  • ¼ cup sugar
  • 1 cup cold butter

For the filling:

  • ½ cup flour
  • 2 cups sugar
  • 1 cup whole milk (or heavy cream)
  • 3 eggs, beaten
  • 4 cups knotweed, peeled and chopped into ½ inch pieces

Put it all together:

  1. In a bowl, combine crust ingredients.
  2. Blend with a fork until it resembles a coarse texture, the size of peas.
  3. Press into a pie pan and bake at 350 for 10 minutes.
  4. In a mixing bowl, add the flour, sugar and milk.
  5. Beat together well.
  6. Add eggs, one at a time, beating each addition well.
  7. Stir in prepared knotweed.
  8. Pour over the crust, and bake at 350 F (175 C) for 30 minutes, or until set.
  9. Allow to fully cool.
  10. Top with whipped cream or ice cream.

Japanese Knotweed Juice

Japanese knotweed juice is a traditional Japanese remedy for a variety of ailments. The plant has been used for centuries in Asia for its medicinal properties, and its juice is said to be rich in vitamins and minerals.

Today, Japanese knotweed juice is available in many health food stores, but you can easily make your own.

Pickling and Fermenting Japanese Knotweed

Pickling Japanese knotweed is a great way to add some zest to your dishes. The fermentation process also helps to break down the plant’s cellulose, making it easier for your body to digest. Fermented Japanese knotweed is rich in probiotics and makes a great addition to any meal.

Japanese Knotweed Puree

This plant is also packed with nutrients, and it can be used to make a delicious and healthy puree. The best time to harvest Japanese Knotweed is in the spring, when the plant is young and tender.

To make the puree, simply rinse the knotweed and remove any tough stems. Then, add the knotweed to a blender or food processor with a little water and blend until smooth.

The puree can be used as a base for soups or sauces, or it can be enjoyed on its own as a healthy snack.

Final Thoughts

If you are looking for a new and interesting way to get outside, consider Japanese knotweed foraging. This fun activity can help you learn about your local environment and provide you with delicious meals.

Have you tried to forage for Japanese Knotweed? What would you make with it? Photos were generously provided by Pia of Busy Hands, Quiet Hearts.

Japanese knotweed pin image
Japanese knotweed pin image

updated 07/25/2022 by Rebekah Pierce

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