Lacking mechanical support tissue, vines may have distinctive allometric laws, which may differ from the predictions of theoretical models for self-supporting plants such as metabolic scaling theory (MST). Here, we collected 260 branches of 12 garden vine species to analyze the allometric relationships between diameter, length, leaf, and stem biomass and the effects of biotic and abiotic factors on the allometric relationships of vine branches using mixed-effect model ANOVA. Our results showed that the scaling exponents of diameter-length of vine branch had significant inter-species differences and were higher than the predictions of MST. Besides, the exponents of herbaceous vines were higher than woody vines. However, leaf-stem biomass of vine branches showed isometric relationships, which supported the predictions of MST and there was no difference among species and life forms. Both biotic and abiotic factors had weak effects on exponents of allometric relationships, while significant effects on constants. These results confirmed that vines invest more in elongation growth compared to self-supporting plants, but the partitioning of biomass follows a strict biophysical constraint. Our findings emphasize the significance of mechanical support tissue proportion in plant stems, which is a critical determinant in allometric scaling relationships.