The stem, often called the rhizome because it roots and shoots adventitiously and can sometimes be found below the water line, is grated finely to make a paste. However, the leaves are quite good as well, and there are several leaf preparations that can be done to bring out the flavors more. I think wasabi's scarcity both as a plant and as food is due to its slow growth rate (18-24 months to harvest the stems) and its need for wet, mild (Japan-like) growing conditions.
https://www.researchgate.net/p...
