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Is Japanese knotweed safe to eat?

Is Japanese knotweed safe to eat?

Japanese knotweed ready to cook

Foraging, the gathering of wild food for free from its natural habitat, was once the domain of upmarket chefs, but since the pandemic it’s hit the mainstream. Foraging courses report being fully booked in months in advance, ‘wild’ food dominates restaurant menus and the hashtag #foragingtiktok is currently followed by 114 million people worldwide.

Japanese knotweed sundae, anyone?

When you hear of all the horror stories in the press about Japanese knotweed it is easy to believe that it’s a dangerous hazard. Pictures of knotweed growing through cracks in concrete, taking over people’s gardens and generally causing a nuisance, are all over the internet. The word ‘triffid’ is never far from people’s lips when they talk about the plant. Consequently, there are many who believe it to be a harmful to human health. In fact, nothing could be further from the truth.

It is completely safe to touch and is, in fact, edible. With a taste reminiscent of a lemony rhubarb, Japanese knotweed features in a whole variety of both sweet and savoury recipes, including purees, jams, sauces, fruit compotes, soups, wines, ice cream and even gin!

Knotweed is however only edible for a short part of its lifecycle, before the soft red-purple stems, which look rather like asparagus, turn hard and woody around May.

Medicinal properties

Knotweed contains many naturally occurring complex compounds which can have both positive and negative effects on our bodies. It is known to have some medicinal properties, with high levels of resveratrol, a polyphenol that supports heart and brain health. It can be used in treatments for Lyme’s Disease, cardio-vascular disease and indigestion, but its ability to thin blood could also lead to health problems for certain people. High quantities of oxalic acid in the plant can cause kidney stones.

Chemical cocktail

The main reason to avoid eating Japanese knotweed is that there’s simply no way of telling whether it’s been treated using herbicides over the course of its life. Glyphosate-based herbicides such as Roundup are commonly used to kill the plant, but the infestation needs to be treated over two or three growing seasons to be effective and even then, the rhizome often remains alive beneath the ground and can suddenly start to regrow. So unless you can be certain that the plants have not been treated, it’s best to give them a miss.

Breaking the rules

In the eyes of the law, transporting, or disposing of viable Japanese knotweed without a licence is actually a criminal offence – which includes picking it and taking it home! So, whatever the celebrity chefs say, Japanese knotweed is one plant that should be left firmly off the forager’s list.

If you don’t fancy knotweed for dinner and would like to have it professionally removed, please get in touch. We have a variety of Japanese knotweed removal techniques suitable for all jobs.

Robert Spaceman

“We had a large stand of bamboo removed, thinned, contained and replaced. The customer service has been first class. Joe and Jason were fabulous and kept me well informed at all times”.