For as long as I can remember, I’ve watched Japanese knotweed creep up and spread over the wetlands near my house. The species is invasive, and the city has through several different attempts to eradicate the plants and allow the native species to return- all of these attempts have been unsuccessful. Although I’ll always have a strong feeling of resentment for the plant that has taken over the wetlands and would love to see it removed, I have recently learned of a redeeming factor that makes me appreciate it a little more- it’s edible.
As knotweed grows to maturity in the summer and fall, it is a tall, dry and woody plant. However in the spring, the young knotweed shoots are crisp and juicy stalk that is often likened in taste and texture to rhubarb (although they have a gentler, more lemony taste than their more well known cousins). When you first see the shoots emerge it is time to start harvesting and eating, because they will grow rapidly into hard, inedible reeds before you know it. Knotweed is a robust and resilient plant that is native to East Asia, but can be found in all sorts of places across Europe and almost every one of the United States.
When you go to harvest your knotweed, please make sure you know how the area is treated- some of the plants might be sprayed with harmful herbicides to try and suppress the knotweed population and not safe for consumption. Only eat if you are sure your knotweed is safe, and then make sure to wash it carefully and remove the leaves- much like rhubarb the stems are delicious but the leaves are poisonous.
After finding out that knotweed is edible, I wasn’t quite sure what to do with it. I made some jam, which was pretty good, but I always prefer a savory application when possible. I finally was inspired to try a spicy, sour brothy soup, filled with rice noodles, mushrooms and of course Japanese knotweed. By using garlic, ginger, jalapeños, onion and shiitake mushrooms I built up a savory and spicy base to the broth. By cutting the knotweed into smaller pieces it was easier for more of the sour flavor to play with the rest of the savory, spicy broth.
The final part of the soup is the toppings- I found spicy radish sprouts at the store that added a wonderful, spicy crunch to the broth, but any (or no) sprouts would also be fine. Sriracha, cilantro and green onions are also great additions to the soup. The rice noodles are prepared by first soaking them in warm water, and then adding them to the pot in the final moments of cooking. If you think you will have leftovers (which you very well might- I tend to cook for 8 when I should be cooking for 2), you might leave out the noodles and serve them instead in the individual servings to prevent them from becoming soggy. If you’re not a fan of brothy soups, you can always add more vegetables or some tofu to make it more hearty. Leave me comments and let me know if you try this recipe, or if you have ideas of other knotweed applications!
Sour Japanese Knotweed Soup
- 1-2 TBSP oil
- 2 cloves of minced garlic
- 1½ TBSP fresh minced ginger
- 2 cups of shiitake, sliced (substitute with a different mushroom if necessary)
- 1 TBSP soy sauce
- 1 medium sized onion, diced
- 1 jalapeño, cut into thin discs (If you do not like spicey food, remove the jalapeño seeds or use less pepper)
- 4 cups of knotweed, leaves removed and carefully washed, chopped into ¼ inch thick half-moons.
- 1 sheet of nori in strips OR 1 tsp of dulse
- 1 tsp cayenne
- 1 star anise pod
- 2 bay leafs
- 1 package of rice noodles, around 7 oz
- 8 cups water or vegetable broth
- Salt and pepper, to taste
Toppings/Sauces (As many or as few as desired)
- Chopped green onions
- Thai basil
- Sprouts (I used a spicy radish sprout, with delicious results)
- Sriracha or other hot sauce
- Garlic chili paste
- Soy sauce
1. Place the rice noodles in warm water and leave for the length recommended on the box. After that time is up, drain the water. If they don’t seem entirely cooked at this point that is fine- they will be thrown in the soup at the end and have some time to cook more.
2. While the noodles are soaking heat the oil in a large pot. At a medium heat add the garlic and ginger, and allow to cook for a few minutes. Add the mushrooms and soy sauce, stirring occasionally. After a few minutes you can add the onions and jalapeños. Stir well and cook and cook briefly before adding the knotweed. Cook for another 2-3 minutes.
3. Stir in the spices, add the dulse/nori and add the water. Bring the soup up to a boil before lowering to a simmer. Allow the soup to simmer for 10-15 minutes, or until the vegetables taste cooked through and the sour flavor from the knotweed has permeated the broth. When you feel the broth is ready, stir in the soaked rice noodles* and let it cook until they soft- this shouldn’t take more than a minute.
4. Serve with your preferred toppings.