Spring cabbage (Brassica oleracea var. capitata L.) is a crop type in which sowing is performed in fall and harvesting in spring. The flower bud differentiation, explained as the phase transition from the vegetative phase to reproductive phase, is induced by chilling after a certain plant size, then the risk of premature bolting is triggered by long days and high temperatures. Farmers empirically avoid bolting by selecting suitable varieties and sowing days. However, climate change may increase the risk of premature bolting. The objectives of this study were to evaluate the relationship between the number of head leaves at flower bud differentiation and premature bolting, and to develop a model to predict flower bud differentiation and the number of head leaves using data on the daily cumulative temperature. Firstly, we found that the risk of premature bolting was high for the ‘Kinkei-201’ cabbage variety when the number of head leaves (> 1 g) was less than 6.5 leaves in the flower bud differentiation period. The number of head leaves (> 1 g) (y) was estimated by the daily cumulative temperature (x): y = 0.0248x − 24.485 to 28.613, depending on year. The flower bud differentiation period was estimated based on the concept of the developmental rate (DVR) and the developmental index (DVI), in which the value of DVI at sowing was defined as 0 and that at the flower bud differentiation period as 1. Each parameter’s response to the cold treatment stage (RS) and the response to chilling (C) was estimated based on the daily mean temperature. The DVR model predicted the flower bud differentiation period in 2010–2014 with a root mean squared error = 5.3 days (without outliers). Therefore, the risk of premature bolting is predictable by estimating the number of head leaves (> 1 g) at the flower differentiation period using data on sowing date and mean temperature.

春季白菜（芸苔变种capitataL.）是一种作物类型，其中秋季播种，春季收获。花蕾分化（解释为从营养期到生殖期的相变）是由一定植物大小后的冷藏引起的，然后，漫长的白天和高温触发了过早抽ing的风险。农民从经验上通过选择合适的品种和播种天数来避免抽ing。但是，气候变化可能会增加螺栓过早的风险。这项研究的目的是评估花芽分化时的头生叶数量与过早抽ing之间的关系，并建立一个使用每日累积温度数据预测花芽分化和头生叶数量的模型。首先，我们发现，“ Kinkei-201”白菜品种在花芽分化期的头叶数量（> 1 g）少于6.5片叶子时，过早抽插的风险很高。通过每日累积温度（x）估算出头叶的数量（> 1 g）（y）：y = 0.0248x-24.485至28.613，具体取决于年份。根据发育率（DVR）和发育指数（DVI）的概念估算花芽分化期，其中将播种时DVI的值定义为0，将花芽分化期的DVI值定义为1。根据每日平均温度估算参数对冷处理阶段（RS）和对冷气（C）的响应。DVR模型预测了2010–2014年的花芽分化期，均方根误差= 5。3天（无异常值）。因此，通过使用播种日期和平均温度的数据估计花分化期的顶叶数量（> 1 g），可以预测过早抽头的风险。