What follows here isn’t about guiding or gear. It’s a place to note the origins of place names and old river records, whenever something catches the eye.
Driving back from a trail in eastern Hokkaido, the size of the rawanbuki caught my eye through the car window again. Native to the Rawan district of Ashoro, this butterbur grows 2 to 3 meters tall with stems up to 10 centimeters across. It’s considered Japan’s largest butterbur, and has been designated a Hokkaido Heritage site.
Not Genetics — Water
What causes it to grow so large stayed unclear for a long time. It’s tempting to assume the plant itself is a special variety, but that’s not the case. A joint study begun in 2015 by Kyushu University’s Hokkaido Experimental Forest — researchers Tomokazu Chiwa and Yasuhiro Utsumi — together with the Ashoro Fossil Museum, found that the main factor is the abundance of nutrients in the water of the Rawan and Moashoro rivers. Nitrogen, phosphorus, potassium, magnesium, and calcium, the nutrients plants need to grow, run at roughly ten times the concentration found in ordinary river water. The findings were published in the international journal Scientific Reports in January 2021.
The Rawan River’s source is Lake Onneto, at the foot of Mount Meakan. JA Ashoro, the local agricultural cooperative, also points to variation within the Akita butterbur species, the basin’s particular climate, and volcanic ash soils from Mount Meakan as compounding factors. Transplanted elsewhere, the plant doesn’t grow the same way — it’s a phenomenon specific to this particular ground.
Under the Leaves of the Korpokkur
The name Rawan is itself thought to come from Ainu. The area also carries the legend of the Korpokkur, small people said to live beneath butterbur leaves. Standing among leaves wide enough to serve as an umbrella, that legend isn’t hard to picture.
Taking seedlings or seeds from the site is prohibited.
The only connection here to packrafting is having seen it on the way back from a trail in eastern Hokkaido — but the size of it has stuck.
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