Russ says to harvest Japanese knotweed stalks at the “wild rhubarb” stage, which typically begins around the first week of May in southeastern Massachusetts. Look for stalks about 18-24 inches long, cut the fattest of them at ground level, and lop off the top cluster of leaves. At home, peel the stringy outermost layer off of each stalk; Japanese knotweed stalks are hollow, so don’t peel too deeply or all you’ll have left is the hole. You can eat the tart, juicy, crunchy stalks raw or chop them up to use in any recipe in place of rhubarb.
• 1 cup flour
• 1/3 cup confectioners sugar
• 1/3 cup butter (cold)
• 2 eggs, lightly beaten
• 1 cup sugar
• 1/4 cup flour
• 1 teaspoon vanilla extract
• 1 teaspoon ground cinnamon
• 1/2 teaspoon allspice
• 1/2 teaspoon grated nutmeg
• 3 firmly-packed cups peeled Japanese knotweed stalk
pieces, (approximately 3/4-inch pieces).
Preheat oven to 350 F. Grease an 11” x 7” baking pan. Put crust ingredients into a food processor and pulverize until mixture resembles coarse crumbs, or cut butter into combined dry ingredients with two knives. Press crust mixture into the bottom of the baking pan and bake for 12 minutes.
Meanwhile, place all the filling ingredients except the knotweed into a bowl and mix together; then stir in the knotweed pieces. Pour filling mixture over the warm crust and spread evenly. Bake for 35-40 minutes or until a toothpick stuck into it comes out clean. Cool on a wire rack. Cut into brownie-sized pieces and serve warm.