Long-Term Temporal Variability of Flowering Day of Red Spider Lily (Lycoris radiata)

In Japan, the flowering of the red spider lily (Lycoris radiata) marks the autumn equinox. To evaluate the effect of climate change on Japanese people’s sense of seasons and this cultural ecosystem service, we examined the spatiotemporal variability of the flowering day (FD) of red spider lily at 9 sites (Maebashi, Choshi, Nagano, Kanazawa, Shizuoka, Tsu, Nara, Wakayama, and Okayama) over the past 60 to 70 years through its relationship with the autumn equinox. (1) Delaying trends were statistically significant (0.12–0.16 days per year) at 4 sites (Nagano, Tsu, Nara, and Wakayama). (2) Bayesian inference analysis with a beta distribution showed that the probability of FD being later than the autumn equinox has increased in the 2010s at all sites. (3) The year-to-year variability of FD was positively correlated with average temperature during the period of flower stalk elongation (late August to mid-September) at 7 sites (except Nagano and Shizuoka). These results suggest that the probability of FD being later than the autumn equinox will increase under further warming during the period of flower stalk elongation, thus affecting people’s sense of seasons and this cultural ecosystem service.