Spider Lilies-Flowers That Come Out Around Autumnal Equinox Day It was autamanl equinox day yesterday. Japan has a unique custom that people visit graves on equinox days. Spider lilies come out around autumnal equinos day every year, so I thought the bloom of the flowers had something to do with the hours of daylight. However, they opened up very late last year. It was extremely hot even in September and that seemed to be the reason for it. Not the day length but the temperature was the condition for the flowers to bloom. It was a new discovery for me. They are in full bloom now this year.