Sansho spices, also known as Japanese pepper, come from the Zanthoxylum piperitum small tree. They are said to have arrived from China during the Heian Period, and it was first mentioned in important historical documents such as the Gishi-Wajinden and Kojiki.
Used to flavor many dishes, it was appreciated for its medicinal properties against heat, diarrhea and coughs. Nowadays it is common to find sansho on the market, but the most widely cultivated variety is the Asakura sansho, whereas Arima sansho is a specific variety from the Arima region, which occurs in the wild and has a different, stronger taste.
There was a strong tradition in Arima region to eat the flower, fruit, leaves and skin of the spice. Arima is indeed well known for this spice, and there are many dishes called Arima sanso in Japanese cuisine, which contains sansho to give a spicy flavor. The name was given because of the strong gastronomic culture around this spice in the region, but nowadays the sansho contained in most dishes is Asakura sansho.
Indeed, until the 1960s there was a culinary tradition among families in Arima to use the wild Arima sansho but it is now disappearing. One of the reasons of the disappearance of this tradition is the fact that people were very secretive about where the fruit-bearing trees were, and never spread the word outside the family. Nowadays it is difficult to find the wild tree but some species have been rediscovered on the Mount Rokko and local communities have started projects to grow the tree.
The spice has been used as a basic spice in Japanese cuisine. Different parts of the fruit can be used for different culinary purposes. The young leaves are used for simple soups, for flavoring miso, and they can also be grilled. If boiled with soy sauce, the fruit, with its kind of small berry, can be perfectly paired with some sake. The unripe ones are called blue sansho and can be used for braising and pickling. In autumn, the ripe fruit can be used granulated for grilled eel. This ripe sansho is used for shichimi togarashi, a general mix of spices in Japanese cuisine. Dishes such as "Arima-braise" and "Arima-grill " all contain sansho, which gives a slightly spicy flavor.