Abstract: With 82 ornamental crabapple cultivars as the research object，the flowering phenology at initial flowering stage（S₁），full blooming stage（S₂）and end flowering stage（S₃）was observed and studied systemly to provide references for the building and maintenance of crabapple gardens，for the excavation and development of special crabapple traits，and for the oriented breeding of crabapple with special flowering phenology. The results were as follows：According to the‘Hou’area distribution（five days is a‘Hou’in Chinese）of S₁，82 ornamental crabapple cultivars were divided into five major flowering sequence groups：Very early group（VE），early group（E），medium group（M），late group（L），and extremely late group（EL），and flowering days interval between the earliest and the latest flowering variety was as long as 22days. According to flowering days from S₁ to S₃，with three days as level differential，82 crabapple cultivars，of which average flowering days was（11.4 ± 2.8）d，were divided into five major groups：Very short group（VS），short group（S），medium group（M），long group（L）and very long group（VL）. Based on flowering phenology frequency statistics，cumulative cultivar frequency index（CFI）functions at S₁，S₂ and S₃ were constructed respectively. It is found that the function linear slope values（i.e. k values）of S₁，S₂ and S₃ were different significantly–k₁（6.312）< k₂（6.821）< k₃（9.1557），which reflected a slow to fast rhythm changing trend in flowering phenology from S₁ to S₂ to S₃. Also，Ornamental cultivar diversity index（CDI）function was constructed，which provided a new reference frame for evaluating the whole flowering appreciation value of the 82 cultivars. Based on CDI function，the whole flowering appreciation period of 82 cultivars were divided into six typical phases：start-up period（P₀），fast rising period（P₁），high and stable period（P₂），fast falling period（P₃），window period（P₄）and low index period（P₅）. It is worth mentioning that in P₁–P₃，CDI ≥ 12.4% and the lasting time was up to 21 days，and in P₂，CDI ranges from 75.4% to 80.2%，and the lasting time was 3 days.Based on the two-dimensional data of flowering days（L）of 82 cultivars and its respective mean daily maximum air temperature（T）during the flowering period（S₁–S₃），and with T = 23 ℃ and T = 27 ℃ as critical air temperature points，the three piecewise coupling functions between L and T were fitted respectively. It is found that the coupling coefficient（R²）between L and T were different significantly for the three cultivar groups distributed in different air temperature zones. Fifty-two cultivars distributed in air temperature zone A（T = 19.2–22.9 ℃），21 cultivars distributed in air temperature zone B（T = 23.0–26.9 ℃），and 9 cultivars distributed in temperature zone C（T = 27.0–32.0 ℃）. That indicated the relativity of flowering days，which depends on both genetic and air temperature factors. When T ≤ 23 ℃，the genetic base was the dominant factor for flowering days，whereas when T ≥ 27 ℃，the daily maximum air temperature turned into the dominant factor. Also，when T = 23.0–26.9 ℃，the genetic base and the daily maximum air temperature both were the dominant factors for flowering days.

Key words: ornamental crabapple, cultivar group, flowering period, phenological sequence, phenological rhythm, cultivar diversity index