Japanese knotweed is terrible for your home, but it sure is delicious
It’s green, it spreads fast and it is not something any homeowner wants to discover they have. Japanese knotweed pushed its way back into the news this week after a clump of the plant growing in a west London garden led to a house buyer taking his seller to court for not being open about the property’s sitting tenant. But when I heard about it, I confess that my first reaction was lucky him!
Of course knotweed is terrible if you have it in your house. It’s considered one of the more virulent invasive species in the country and is almost impossible to get rid of. But knotweed is also delicious. As long as your clump hasn’t been injected with weedkiller in the last few years, it is a superfood. I’ve had it in fruit fools and used it to infuse gin. At Silo, a zero-waste restaurant in east London, they serve it grilled in salad. It looks a bit like asparagus.
Japanese knotweed arrived in the UK in the 1800s, introduced as an ornamental plant from east Asia, where it grows alongside predating insects and funghi in low nutrient soils, sending down roots that are metres deep and pushing up through lava to reach the light. So it's tough. Unfortunately this means concrete and tarmac are no match for lava-busting knotweed and it is now one of the most virulent invasive species in the country. You'll definitely want to control it.
It is part of the same family of plants as rhubarb and sorrel, which might make eating it as an eradication strategy seem less bewildering. Not only does it taste like a cross between the two, it is also rich in minerals and vitamins. Knotweed has a long history of being used in traditional medicines – with high levels of resveratrol, a polyphenol that supports heart and brain health – and it is currently being trialled for treating the tick-borne bacteria that cause Lyme disease.
If you need further convincing to eat your way out of a knotweed thicket, look back to its homelands of Eastern Asia for mouthwatering recipes where it’s fermented or preserved in salts. This not only allows knotweed to be consumed later in the year but also reduces the amount of oxalic acid in the plant which can cause kidney stones (oxalic acid is also found in rhubarb and sorrel and plants like spinach).
Eaten fresh as a springtime vegetable, the young stems are plucked when they are the size of pencils and sautéed, stir fried and even covered in a tempura batter, or griddled with a sticky coating of miso, soy, grated ginger and garlic, to give the fast-growing shoots a delicious ending.
Should fatty meats and oily fish be your thing, Japanese knotweed can help you there as well – it makes a delicious mint-sauce style condiment when finely chopped up with mint, fennel and dill, with a generous glug of sweetened apple cider vinegar and a pinch of salt and sugar.
The plant can swing merrily between savoury dishes and sweet. It cooks in the same way as rhubarb, softening down into tender strands that cry out to be stirred through dairy and turned into a fruit fool. If a fool sounds like your kind of way to tackle the tussock, cook 450g of young chopped knotweed stems in a pan with the zest and juice of a lemon and 3 tablespoons of sugar and cook until tender. Leave the fruit to cool before stirring through 300ml whipped cream and 100g Greek yogurt.
The US foraging chef Alan Bergo recommends peeling the stems to remove any stringiness. He is also a fan of pureeing the cooked stems, using the smooth mixture to make sorbets and mousses, and dehydrating them to make fruit leathers. A jar of cooked and pureed knotweed marbled through vanilla custard, stuck back in the freezer for a couple of hours before serving then topped with crumbled meringue nests, makes an easy and elegant dessert.
And it can be fermented into wine or juiced and added to cocktails as a souring ingredient. Wild cocktail guru and foraging guide Mark Williams, from Galloway Wild Foods in Scotland, is an advocate of Japanese knotweed juice vodka cocktails.
And knotweed is just as happy in a bath of gin. To make knotweed gin, try filling a Kilner jar with 500g washed chopped young knotweed shoots, 100g caster sugar and 400ml gin, either alone or with a couple of star anise or cardamom pods, leaving them to soak for four weeks before straining and drinking a victorious toast to your predator skills.
Liz Knight is a forager and wild food chef and the author of Forage: Wild Plants to Gather and Eat, where you can find more recipe ideas for knotweed