Itadori (Japanese Knotweed)

All too often when I look up a plant online to see how other folks are utilizing it I get pages and pages of how to eradicate it before (if) I find anything on how one can use it. Why are we such haters? We need to be lovers people! Japanese knotweed (Fallopia japonica, syn. Polygonum cuspidatum, Reynoutria japonica) is one of those plants that seems to elicit an awful lot of ill feeling but, like all plants, it is truly amazing and deserving of much respect.  The common English name “knotweed” displays such a lack of respect (and ignorance) in itself that from here on I shall use the Japanese name: itadori.

A literal translation of itadori would be pain puller or, removes pain. A name that clearly tells us something about the uses of the plant and the high regard  in which it is held. Plant people of Japan, Korea and China have traditionally used the roots of itadori as an anti-inflammatory, a laxative, for oral hygiene and cardiovascular health, treatment of acute hepatitis, kidney stones, high cholesterol, and skin rashes amongst a host of other uses.

Scientists tell us the plant has anticancer, anti-inflammatory, blood sugar-lowering and other beneficial cardiovascular effects for rodents. It is also believed to extend life spans – probably the last thing a lab rat wants!

Itadori growing alongside a stream in summer

You’ll typically find itadori in riparian ecosystems but also by roadsides, abandoned urban lots or “waste” spaces, i.e., damaged ecosystems. It is a perennial that sprouts tender edible shoots in the spring and will often grow to 3 or 4 metres tall over summer. Growing in thickets it produces an impressive amount of biomass every year. Given that its spirited shoots will grow through the tiniest of cracks in concrete or road surfaces, bursting them apart and mulching with a thick layer of biomass every autumn one of its ecosystem functions may well be re-wilding the city! Its extensive rhizomes and general growth habits would also suggest it may protect areas prone to erosion, such as stream banks, particularly from flooding and stabilize areas where sediment has been deposited.

As a food itadori provides vitamins A and C, antioxidant flavonoids, potassium, zinc, phosphorus, manganese…so the scientists tell us. East Asians have eaten itadori for millennia because they knew it was good for them. It felt good.

Itadori is prolific producer (why it scares some people so much) so if you’ve got access to a patch there’ll be plenty of shoots for consumption. Over harvesting is not an issue – if anything it stimulates the production of more shoots. There’ll be more than you can eat so its a good plant to preserve for leaner times.

Edible itadori shoot

The shoots are best harvested when 15 to 20 centimetres tall. Earlier rather than later in the spring.

So, if itadori is usually harvested in spring why am I writing about it now? We have just eaten some itadori that we preserved this past spring and it was so good that I felt the need to sing its praises immediately.

Salted Itadori

The  traditional method of preserving itadori in Japan, and still used  on the island of Shikoku, is salting. It is not a fermentation as the large amount of salt used in the first step of the process will inhibit the growth of all bacteria and yeasts including lactobacilli. Even if lactobacilli were to turn up in the second stage of the process it would not be very strong. So, the finished product will not have the strong sourness of a lacto-ferment and will be very salty. The saltiness can be reduced before eating.

Peel the skin of the itadori, cut in to convenient lengths and layer in a crock or glass, enamel or food grade plastic container with generous amounts of salt (approx. 20% of the weight of itadori).

Place a weight on top so that all of the itadori is submerged in the liquid that comes out.

After 10 days drain the liquid and rinse the itadori. In these first 10 days the oxalic acid in the itadori will be drawn out by the salt.

After rinsing return the itadori to the container, again layer with salt although this time each layer is just sprinkled lightly with salt. Place a weight on top so the itadori is eventually completely submerged by the liquid that comes out.

Itadori being layered and sprinkled with salt in the second stage of the process

To use remove some itadori from the container and soak in water for half a day, changing the water a couple of times, to remove some of the saltiness. Better still, if possible, is to leave it under running water (in a stream, for example) for half a day. It is delicious raw or cooked. As long as the itadori is fully submerged in its juices it should keep for a very long time.

Fresh Itadori

To prepare freshly harvested itadori shoots: Discard large tough leaves. Remove the tough outer layer of the shoot. Boil the peeled shoots for a couple of minutes. Soak in water over night. This process will remove oxalic acid from the shoots. Next day rinse the shoots and eat as is or cook with other ingredients.

Its really very tasty and also very versatile. The dish below is itadori sauteed in sesame oil, with shoyu, mirin (sweet sake) and roasted and crushed sesame seeds.

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