| In order to grasp and predict the growth of head lettuce, a growth model was established with head lettuce cultivation in open fi eld as material. By analyzing the matching temperature of fi eld phenotypic data of head lettuce, the growth models of the plant maximum diameter, plant height, leaf number, leaf length, leaf width, bulb height and bulb width were established in spring and autumn in Shandong. In order to improve the effi ciency of fi eld investigation, the correlation coeffi cient among the growth indexes was analyzed, and it was determined that the growth of head lettuce could be understood only by investigating the three items of plant maximum diameter, leaf length and bulb height. The growth of head lettuce was predicted by the daily maximum temperature, daily minimum temperature and growing days. When the difference between the predicted value and the actual value was more than 5%, the programme of planting and management should be adjusted in time to ensure the normal growth of head lettuce. |