Abstract:

Climatic indices for initial flowering in Osmanthus fragrans were analyzed statistically by comparing the phenological data and climate data from 1956 to 1984 and from 1999 to 2003 in Dongshan County, Suzhou, Jiangsu Province, China. The results showed that the initial flowering date of O. fragrans was closely related to daily minimum temperature and relative humidity. For early flowering O. fragrans, initial flowering occurred 3 to 12 days later following a condition that the daily minimum temperature of 10-day-moving-average (DMTMA10)≤23.0 ℃ and the daily minimum temperature <22.0 ℃, or 12 days later following a condition that DMTMA10 stays between 23.0 and 25.5 ℃ and the daily average relative humidity (DARH)≥88% for 3 or more than 3 days. It would not get flowering if the DMTMA10>25.5 ℃. For late floweringO. fragrans, initial flowering occurred 4 to 12 days later following a condition that the daily minimum temperature of 9-day-moving-average (DMTMA9)≤20.0 ℃ and the daily minimum temperature <19.5 ℃, or 6 days later following a condition that DMTMA9 stays between 20.0 and 21.5 ℃ and the DARH≥88% for 3 or more than 3 days. It would not get flowering if the DMTMA9>21.5 ℃. The date of initial flowering of early floweringO. fragrans and that of late flowering O. fragrans were significantly correlated (r=0.443 8, n=34). The initial flowering date of late flowering O. fragrans is, on average, 15 days later than that of the early flowering O. fragrans. The initial flowering date of both types of O. fragrans during 1999 and 2003 was postponed 7-8 days compared with that during 1956 and 1984 in Dongshan County due to global climate warming.

Key words: Osmanthus fragrans, Initial flowering, temperature, Indices, Climatic change