Kuwai (Arrowhead Tubers) (クワイ)
Kuwai (arrowhead tubers or Sagittaria trifolia) are perennial aquatic herbs in the Alismataceae (water plantain) family and are also called 'tagusa', 'enbi-kusa' or 'kuwae.'
There are theories that the word kuwai (arrowhead tuber) originated from 'kawa-imo' (river potato) or that it evolved from 'kuwai-guri'.
There is a theory that they were introduced from China to Japan at the beginning of the Heian Period and a theory that they were brought from the Korean Peninsula in the 16th century.
The leaves are shaped like arrowheads. They are grown in paddies and there are several varieties including blue arrowhead tubers and white arrowhead tubers.
They are distributed widely from temperate to tropical areas in Asia and throughout Europe and the United States.
In Europe and the United States they are mainly used as ornamental plants.
Use as a food
In Japan and China the tubers are eaten, and particularly in Japan they are considered a good omen as they sprout, and it is customary to eat them in boiled dishes for the New Year.
The tuber is peeled and soaked in water to remove the harsh taste before cooking. They have the bittersweet taste of lilybulbs and one can enjoy their texture which is not soggy when boiled.
The black arrowhead tuber (Kuro Kuwai or Karasu-imo) used in Chinese cooking is a big black arrowhead in the Cyperaceae family and is a different variety of plant from the Japanese arrowhead, and is available in cans as water-boiled arrowhead, however there is evidence that this has also been used as a food from ancient times in Japan and has been unearthed from Jomon Period remains in Kameoka, Aomori Prefecture.
Fukuyama City, Hiroshima Prefecture (produces 80% of the arrowhead tubers grown in Japan)
Koshigaya City, Saitama Prefecture (second only to Fukuyama City in production volume)
In Suita City they produce a small variety called Suita arrowhead (one of the Naniwa variety of vegetables).
Until the Meiji Restoration they were offered as presents to the Imperial Court and the name Suita arrowhead became widely known as it was featured in a poem by Shokusanjin, 'remembering de-boned conger with Suita arrowhead and Tennoji turnip.'
However currently only enough are produced by an association for their preservation and the volume of production is not enough for shipment to other cities. At one stage they were even in danger of becoming extinct.
Saitama Prefecture boasts a production volume second only to Hiroshima Prefecture however housing developments have encroached and the production has tended to decline in recent years. In Koshigaya City which is the biggest producer of arrowhead in the Prefecture, a local research association has produced the world's first beer using arrowhead tubers and they are making an effort to spread the consumption of arrowhead tubers.
In Fukuyama City, Hiroshima Prefecture, they sell arrowhead shochu (liquor) called 'Fukuyama Sodachi' ('made in Fukuyama') as a limited seasonal product.