That's because of the lack of light, and the return of cyanidin.
When the green Paris flower bud is opened, it is white, and when the flower bud is green.
Longevity is native to Africa. It likes warm, slightly humid and sunny environment. It is not cold resistant, and the suitable temperature for growth is 15~25 ℃. If the high temperature in summer exceeds 30 ℃, the growth is blocked. In winter, the indoor temperature should not be lower than 12 ℃. It is better to have 15~18 ℃ in the daytime and more than 10 ℃ at night. When the temperature is lower than 5 ℃, the leaves turn red, and the flowering period is delayed or cannot blossom normally, affecting the festival viewing. In winter and spring, if the room temperature exceeds 24 ℃, flowering will be inhibited. If the temperature is about 15 ℃, the longevity flowers will bloom continuously. Longevity flower is drought resistant and has no strict requirements on soil, and fertile sandy loam soil is preferred. Generally, the pot is changed once every spring after the flower withers, and the pot soil is made up of 4 parts of rotting leaf soil, 4 parts of garden soil, and 2 parts of river sand, plus a small amount of mixture. Longevity is a short day plant, which is sensitive to photoperiod. The plants with good growth and development can flower buds after being treated with short day light (8-9 hours per day) for 3-4 weeks.