I point to the 99-year-old celebration as I know with white Kotobuki.
100-1 = 99. It becomes the white when I subtract one from 100 of the kanji. From this, white Kotobuki points at a 99-year-old (the celebration) thing, and this gentian with the name of white Kotobuki is a gentian lucky at all having a meaning called << in hope of health and longevity >>.