Tree-like branching networks are conduits for mass transport in many natural systems. Because precisely determining conduit-matrix mass transfer requires exact knowledge of dendrite geometries, interdomain mass exchange rates are often described using the concept of effective mass-transfer. We present a direct association between average geometric properties of dendritic networks and mass transfer. We show that the value of the mass-transfer rate coefficient can be estimated directly using a physically based relation that requires no knowledge of the specific network geometry.