This is a two-part chapter, so I've saved half the meaning of Japanese Rowan for next time.
But for some additional info, the Japanese Rowan, or Nanakamado as its known in Japanese, gets its name for being infamously hard to burn. The name is literally 7 (nana) hearths (kamado), that you could stick it in the hearth 7 times before it caught fire. This gave it an association with things taking great care and effort to accomplish. Some roads in Japan are actually lined with Japanese Rowan for the reason it's meant to make drivers show more precaution.