Leafing intensity, which refers to the number of leaves per unit shoot size, is a key architectural trait that is closely linked to plant hydraulics. However, it remains unclear how leafing intensity is regulated by deeper water tables and greater plant heights (i.e., with both necessitating longer hydraulic paths to foliage). As there are diminishing photosynthetic returns from incrementally increased hydraulic support costs with longer hydraulic paths, we predict that leafing intensity would decrease accordingly. To test the prediction, we examined the hydraulic constraints on leafing intensity in a desert riparian species, Populus euphratica. We sampled 1863 shoots from 96 trees with varying heights at contrasting water table depths along the Tarim River corridor in Northwest China. Results showed that midday shoot water potentials decreased with water table depth and plant height. P. euphratica trees had fewer leaves for a given shoot length with deeper water tables, while the increase in leaf number per unit increment of shoot length was constant across water table levels. Although the increase in leaf number per unit increment of shoot length was slightly higher in tall P. euphratica trees, they had fewer leaves at the onset of shoot elongation, and at the grand mean of shoot length across height classes. Overall, the lower leafing intensity with increasing water table depth and plant height highlights the role of hydraulic path length in regulating leaf-shoot allometry. These results also suggest the functional significance of leafing intensity in equilibrating photosynthetic gains with water supplies under varying hydraulic constraints, especially for plants inhabiting drylands.