Turning invasive plants into something sweet

Some people just love plants, as I’ve written elsewhere, and we humans have a rich history of cultivating, caring for, and consuming the plants around us. As we moved around the world, we brought plants with us, spreading them to new environments. This strategy has almost always been a Win for the plants we moved, has generally been a Win for us, but has at times been a catastrophic Loss for the “native” plants that weren’t planning for some random relative from across the world to put down roots so suddenly.

One such example is Japanese knotweed (Fallopia japonica), an herbaceous plant in the knotweed and buckwheat family of Polygonaceae, that was brought to the UK in the 1820s and eventually ended up in the US. Knotweed grows in thick colonies that can crowd out other species and is so resistant to cutting and excavation that it is considered one of the 100 worst invasive species in the world.

In the Boston region, you can find knotweed growing in most un-mowed green spaces, from Franklin Park to Alewife Brook Reservation and even in Central Square, Cambridge!

A knotweed infestation in Central Square, Cambridge

From the perspective of park managers, dog-walkers, birds, and pretty much every other species of plant, Japanese knotweed is bad news. But it is worth celebrating the resilience, durability, and spunk of this single species that is singlehandedly changing the biodiversity of our urban green spaces. One more reason to celebrate this plant is its edibility. Japanese knotweed is a classic plant to forage (harvest from nature for eating) and can be prepared similarly to asparagus, rhubarb, and more! Plus, when harvesting knotweed at the right time of year (early spring), it makes a satisfying “popping” sound.

I recently made some tasty apple-knotweed jam in celebration of this detestable and delectable plant. Even though foraging for knotweed won’t have an appreciable impact on its population, I feel some satisfaction knowing that I can actively “scold” the plant for wreaking havoc on our urban ecosystems while simultaneously appreciating its merits.

Peeled apples and freshly foraged knotweed, ready for jamming!

So, you want to know how I made apple-knotweed jam? I essentially followed this recipe but replaced about half the apples with minced knotweed. Instead of using commercial pectin, I wrapped the apple peel and core (seeds removed) in cheesecloth and boiled it along with the jam to release some additional natural pectin into the mix. Also, I did not use cardamom. Yum!

Jars of homemade apple-knotweed jam.

Warning! Do not harvest or consume wild plants unless you are confident of their identity and you do so in a safe and sustainable manner (for example, don’t harvest from places that may have been sprayed with herbicides). While foraging for invasive species is generally applauded, the same does not apply for all native species.

PS: If you’re in the Greater Boston area and looking to learn more about wild edible plants, consider coming on a foraging walk with Russ Cohen, local foraging guru!

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