Modeling the three-dimensional (3-D) shape of plant stems is important in the study of plant growth in precision agriculture. To construct a 3-D model of real plant stems from images quickly, a novel volumetric method based on line-based models is proposed. Line-based models are constructed on the coarse 3-D skeleton of the plant stems, then carved with respect to silhouette consistency. The surface points on the plant stems are calculated from line-based models. Finally, a mesh surface model can be extracted from the surface points. The proposed method can give precise results together with low time complexity and space complexity. Experiments based on both synthetic and real data are presented to evaluate the speed and preciseness of the proposed method.