Japanese knotweed (Polygonum cuspidatum syn. Fallopia japonica) is an invasive plant with juicy, sour, hollow stems. It is often compared to rhubarb both in taste and texture (crunchy when raw, breaking down into a soft paste when cooked).
I’ve written about how to find and identify this plant here before, or here’s a video that will introduce you to Japanese knotweed. Always be 100-percent certain of your identification before eating any wild plant.
Whatever you do, no not introduce this plant into your area. If it’s already there, make the best of the situation by enjoying its tangy taste raw or cooked, in savory recipes or sweet ones like the one below. But if it doesn’t grow near you be grateful, because it is one of the most invasive and difficult to eradicate plants I know. Sustainability is not an issue when harvesting knotweed!
"Use like rhubarb" is the usual culinary advice with this plant because it has a similar sourness and, like rhubarb, transforms from crunchy to fall-apart soft when cooked.
However, Japanese knotweed's flavor includes grassy notes that rhubarb lacks. That can be pleasant or not depending on how this ingredient is used. Those grassy overtones can be interesting in savory recipes, but weird in deserts. If you want to minimize that “green” aftertaste, be sure to peel the stalks (thanks for the tip, John Kallas).
This recipe is from my book The Forager’s Feast: How to Identify, Gather, and Prepare Wild Edibles.
Yield 16 bars
100 percent of the tanginess in these yummy bars comes from the Japanese knotweed. Frozen knotweed works just as well as fresh in this recipe.
• 1 1/2 cups peeled and finely chopped Japanese knotweed stalks
• 3/4 cup brown sugar, divided
• 4 tbsp water, divided
• 4 tsp cornstarch
• 1 cup rolled oats
• 1/2 cup all purpose flour
• 1/2 tsp salt
• 5 tbsp butter, melted, plus additional for greasing the pan
1. Preheat the oven to 350 degrees Fahrenheit. Lightly grease an eight-inch square baking pan with butter or coconut oil.
2. Combine the chopped knotweed stalks, 1/2 cup of the sugar, three tablespoons of the water in a medium pot. Bring to a boil over high heat, then reduce the heat and simmer, stirring often, until the knotweed softens and starts to fall apart.
3. Stir the cornstarch and remaining tablespoon of water together until you have a smooth paste. Stir the cornstarch into the knotweed mixture. Raise the heat to high and cook, stirring constantly, until it thickens. Remove from the heat and set aside.
4. In a large bowl, stir together the oats, flour, salt, and remaining 1/4 cup of sugar. Add the butter and stir until you’ve got a crumbly but well-combined mixture.
5. Press half of the oat mixture into the baking pan. Spread all of the knotweed filling over the top. Top that with the rest of the oat mixture.
6. Bake for 25 to 30 minutes, until the top is golden brown. Cool completely on a rack, then cut into bars.
Leda Meredith teaches foraging internationally and is the author of several books including The Forager’s Feast: How to Identify, Gather, and Prepare Wild Edibles and Northeast Foraging: 120 Wild and Flavorful Edibles from Beach Plums to Wineberries. You can find more of her recipes and food adventures on her blog and videos.
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