Chilling requirement for native Prunus campanulata Maxim in Taiwan.
P. campanulata is distributed in broadleaved forests at 500-2000 m throughout Taiwan. The chilling requirement for native P. campanulata was determined by comparing flowering date with 4 peach key cultivars, namely Flordared, Premier, TropicSweet and TropicSnow, at Wufeng (Taiwan) from 1996 to 2001. The chilling requirement for the key cultivars and P. campanulata was calculated from the initial date of chilling up to the completion and full bloom using 4 different models, i.e. the number of hours below 12.9 °C, low-chilling nectarine model, Utah chill-unit model and Taiwan chilling model. Results revealed that the chilling requirement of the key cultivars was insufficient during warm winter. Using the Taiwan chilling model, a higher degree of accuracy was obtained compared to other models. The estimated result in terms of chill unit (CU) using the Taiwan chilling model was 190 CU for P. campanulata.