Unzen Takana Mustard (Brassica juncea): is a type of leafy vegetable belonging to the Brassicaceae family. Originally from the area included between the Mediterranean and Central Asia, through China it arrived in Japan, where it has developed local varieties and ecotypes adapting to the environmental and cultivation conditions of the country. In the prefecture of Nagasaki and more precisely in the municipality of Unzen, in the Shimbara peninsula, in the extreme south of Japan, one of the most characteristic of these ecotypes has developed, a takana that develops "knots" at the base of leaf ribs.
Its taste is delicate, slightly spicy but tending to sweet, it is cultivated especially for the leaves but you can also consume the stem, the stalks have a more intense flavour and its scent is reminiscent of horseradish.
In cultivation, it does not suffer the cold, whilst in the heat it will start seeding; being particularly vigorous it can be grown in the South until May. It is sown in seedbed and transplanted about twenty days later, it is not particularly demanding since it derives from a wilderness selection, it is therefore easy to cultivate even for beginners.
 For the reproduction of the seeds, some plants should be allowed to follow their course until they produce flowers, in May, the yellow beauties will be followed by pods that should be harvested when dry and have acquired a brown colour.
 In the kitchen it is versatile and at the first bite it will provide many ideas and inspiration, Japan and Italy, however far away, have a very important culinary tradition in common, the love and attention for the product including its history, and that is how excellences are born.
 We improperly call these vegetables "mustard", this because the term overlaps with "senape" in Italian, the correct definition should be the too vague "Asian vegetables", we will therefore define the Brassica juncea with the term mentioned above.

Insights

We leave an extract from the Slow Food website, which included this variety in the ones of the"Ark of Taste", full link at the bottom.

"It was selected through the efforts of Mine Masugu, a small farmer and owner of a seed store, who after the war decided to cultivate and propagate this ecotype, and made it available to other local farmers. As a result this leaf vegetable has spread throughout the area with the name “Unzen takana with knots”. From the 1960s its cultivation was completely abandoned and replaced by more profitable crops.
A local farmer, Iwasaki Masatoshi, came across some wild plants in 2002, propagated and selected them, and distributed the seeds to local small farmers. This led to the creation of a local movement to recover Unzen takana involving 13 organic farmers, including Iwasaki, who undertake to produce seed for the others. A small workshop run by women transforms this vegetable into traditional Japanese tsukemono. The first plants, harvested in October, are eaten fresh (cooked or raw), while the second and third harvests are processed.
Due to its sweet flavor, with a slight spicy note, Unzen takana is the only Japanese takana which can be eaten raw: all the other ecotypes have a sour flavor and need to be transformed. Tsukemono is the traditional Japanese preservation method for winter vegetables. After harvesting, the takana is dried for half a day, then put in brine and left to ferment in salt in sealed, weighted containers. After about one month more salt is added together with a little turmeric and fermentation allowed to continue. It is ready for eating after about 3-4 months."

https://www.fondazioneslowfood.com/en/slow-food-presidia/unzen-takana-vegetable/