In the book 日本茶のすべてがわかる本 , there is a brief section on Japan’s northern teas (日本におけるチャの北限), as illustrated above.
I was surprised to see Hokkaido, but apparently it is just the northernmost point where tea plants can grow. Some are also found growing in the wild. I further read that in Furubira town, tea plants can be found in the gardens of Zengenji temple.
In Kuroishi city, Aomori tea cultivation used to exist but it seems that these days tea is cultivated by civilians for personal consumption. There are no processing plants for commercial production.
Hiyama in Akita is considered the northernmost active tea production area. Traditional methods using hand are still in use here, which means the amount produced is very small. That makes it a fairly rare tea. I would love to try Hiyama tea someday. Black tea seems to be the prevalent type of tea produced.
Rikuzentakata in Iwate is/was also considered the northernmost tea production but using modern manufacturing methods. Not much is mentioned about this in the book, but reading up on the Internet, tea from this region is known as Kesen-cha. The production was greatly affected by the the 2011 Tohoku earthquake/tsunami disaster as the city was among the worst hit, so it seems like the tea producing activities around the area have slowed.
Commercially well-known tea production areas are Murakami in Niigata and Daigo in Ibaraki.
I have interest in Murakamicha, as I read that green tea produced there are usually blends of few cultivars. Murakami is also famous for its black tea.
I am not familiar with tea from Daigo, known as Okukujicha.
So there you have it, some of the teas found in the northern part of Japan. Most people would not have thought that tea plants can grow in those areas. Even I thought Murakami was the furthest north where tea could be found.
There are just so many teas to try in Japan alone, what more to say the world!