This crumble is a simple and delicious way to use lots of Japanese knotweed! It tastes just like rhubarb apple crumble. The shoots in the picture are the maximum size to harvest. We peeled them and removed the leaves to use them in the crumble. A vegetable peeler works best for this. You should harvest them when they are 1-2 feet tall, and I always prefer to harvest the fattest ones I can find for minimum peeling effort. Some people harvest thinner ones and don't peel them, but the peel can be fibrous just like rhubarb, and I am not a fan of that texture.
Many wild foods require some type of preparation (such as cooking or boiling and discarding water) in order to disarm toxic compound and make them safe to eat. In the case of knotweed, it is recommended to eat only when young, and is usually cooked to reduce the oxalic acid content. The young stalk can be peeled and eaten raw in small amounts if you sprinkle it with salt, let it sit for 15 minutes, and then rinse. This was taught to me by a tea and wasabi farmer in Japan who had knotweed growing in her tea fields (her harvest is pictured below). I made a salad with apple, wild violet flowers, wild watercress and Japanese knotweed stalks (prepared in the way just mentioned) which turned out pretty tasty. They can also be refrigerator pickled in hot brine or cooked into desserts like rhubarb.
Japanese knotweed is not poisonous to humans, but could potentially irritate your GI tract or kidneys. Always, ALWAYS come to a thorough understanding of how wild foods are prepared and how edible they are before eating them.
Here's a great post http://www.eattheweeds.com/japanese-knotweed-dreadable-edible/
Filling:
3 tart apples (any apple you'd use for pie or applesauce)
6 Japanese knotweed stalks (ours were 2 feet high)/ 4 cups chopped (always harvest Japanese knotweed when the shoots are very young in the spring)
2 tsp arrowroot powder
1/4 cup coconut sugar
Topping:
1/2 c coconut oil
1 cup oats
1/2 cup flour (We used a gluten free flour blend)
1/4 cup sugar (we used brown sugar, you could use coconut sugar or maple syrup)
pinch of salt
1/4 tsp cinnamon
Directions:
1. Peel knotweed shoots and chop them into 1/2" pieces.
2. Chop apples into 1/2" pieces.
3. Put both in a pan on the stove on medium heat with a little water and cook until everything is softened (about 10 minutes). Stir to prevent burning and to distribute heat. The knotweed will dissolve much quicker than the apples.
4. Remove from heat and stir in arrowroot and sugar.
5. Pour into 9" square pan and spread evenly.
6. combine all crumble ingredients in a bowl and work together with your hands. Should be like wet granola. sprinkle evenly over the top.
7. Put in the oven, and bake at 375°F for 35-50 minutes