The flavour of JK is somewhere between rhubarb and gooseberries and I have explored the following ways of extracting flavour for drinks:
Raw juice: Either in a hand-cranked “wheatgrass” juicer or in a rotary juicer. The resulting liquid comes out thick and green. It can be used this way (think of it like orange juice “with bits”), but makes for a pretty murky green drink! Passing through muslin has limited effect, but if you leave it in the fridge for 12 hours, the green pulp sinks and you can skim off a beautiful, clear pink juice from the top that makes an excellent light, fresh, crisp acidifier. A commercial centrifuge would work well here.
Cooked Juice: Chop the stems and simmer lightly with a little water for 15 minutes before blitzing and passing through muslin. The resulting liquid looks green initially, but soon turns a pleasing purple colour throughout. Not so light as the raw pink juice, but still an excellent sour mixer.
Infusion in Alcohol: 2/3rds fill a kilner with chopped raw JK then top up with vodka (min 40% ABV). This improves with age, being worthwhile after about 1 month – or try rapid infusion. Sweeten to taste.
Wine: I haven’t made wine with JK or tasted it, but those I know that have rate it highly.
Thoughts on pairings: JK goes extremely well with sweet aromatic flavours. My favourite accompaniement is sweet cicely, whose sweet aniseed and deeper notes work exceptionally well with the sour fruitiness of JK. Vanilla/courmarin flavours such as meadowsweet, sweet woodruff and elderflower also work extremely well. Try adding some to an infusion.
JK straws: The hollow shoots of JK lend themselves very well to use as natural straws that enhance the flavour of the drink. Select one of appropriate length and push a skewer or chopstick up through it, piercing the membranes between segments. Either chop off the tip, or insert a short straw in the top.
I hope this article will inspire some thoughtful experimentation with this remarkable plant. I think it is possible for mindful bartenders and small businesses to generate some very positive stories around japanese knotweed, spreading messages of mindful control, responsible foraging and the gastronomy of “weeds”. But this could all be rubbed out by one incidence of careless disposal – so please be careful!
Japanese Knotweed syrup recipe