Japanese knotweed (Polygonum cuspidatum or Fallopia japonica) is an invasive wild plant that is also a versatile ingredient, but only during the few short weeks of spring when it is tender enough to bother harvesting.
This plant was originally introduced to North America by the horticultural industry as an ornamental because its fast-growing, jointed stalks form attractive colonies that are reminiscent of bamboo. Like bamboo, the stalks are hollow except at the joints, but that's where the similarity ends.
Japanese knotweed stalks are speckled with red (or sometimes entirely red) and have papery sheaths at the joints. Often compared to rhubarb, Japanese knotweed does have a similarly tart flavor but also strong earthy green overtones. Like rhubarb it is crunchy raw but quickly cooks down to a soft, pulpy mass. It is good in both savory and sweet recipes.
When the plants first emerge from the perennial roots in early spring, they shoot straight up. As they get taller, the stalks begin to zig and zag at the joints, eventually branching and becoming as high as 8 feet tall.
The leaves are smooth-edged and shaped like a gardener's trowel. When the plants finally flower, the cream-colored flowers are in clusters and become aerodynamic seeds that spread far and wide, carried by the wind.
The root systems are massive, like huge clumps of twisted driftwood. Even a small piece of a Japanese knotweed root left in the ground will generate a new plant. That fact, plus those wind-born seeds, is why this is considered a dangerously invasive plant. It will quickly crowd out slower-growing plants trying to survive adjacent to it. You don't have to worry about over-harvesting this one!
Japanese knotweed contains the antioxidant resveratrol, the same substance that makes red grapes (and wine) useful for preventing heart disease. The root is harvested commercially in Asia for its medicinal benefits.
But for food, it's the young stalks that you want. Harvest them when they are still tender enough to snap off with a clean break without needing to use a knife. Here's a short video that captures the satisfying "pop" sound Japanese knotweed makes when it is harvested at the right stage.
Once you've harvested tender Japanese knotweed stalks in early spring, give them a soak in a sink full of water. For some reason, ants love Japanese knotweed but this preliminary soak will get rid of them.
Very young Japanese knotweed stalks don't need to be peeled. Try stripping off a bit of the skin of the stalk: if it strips off easily, then the skin is tough enough that it's worth removing it. If it's hard to peel because the skin is too thin, don't bother.
You can freeze Japanese knotweed without blanching it first. It will keep well, frozen, for at least six months.
Hummus-Filled Knotweed Snacks
Raw Japanese knotweed stalks have a celery-like crunch, but also a pleasantly sour taste that kicks up the lemon flavor of the hummus.
1. Choose tender, young Japanese knotweed stalks that are at least 1/2-inch in diameter. Remove any leaves, wash, and then peel if necessary.
2. Cut the prepared knotweed stalks into 1-inch lengths. They will look like short tubes.
3. Use a table knife to fill first one side and then the other with hummus (homemade or store-bought). Serve immediately, or refrigerate, covered, for up to 3 hours.
Leda Meredith is the author of Northeast Foraging: 120 Wild and Flavorful Edibles from Beach Plums to Wineberries. You can watch her foraging and food preservation videos, and follow her food adventures at Leda's Urban
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