Currently, production potato has been decreasing in North Sumatera, is caused by the insufficient availability of seeds quality. Paclobutrazol (PBZ) is a hormone that can increase the rate of assimilation and expand aggregation of acclimatization for tuber regulation. Volcanic ash which functions as an ameliorant in the soil is very useful for increasing nutrients in the soil. The aim of this research was to determine the effect of PBZ on vegetative growth of potato seeds with volcanic ash and the interaction between of them. The PBZ concentration (P0=0.00; P1=150; P2=300 and P3=450ppm) was the first factor in a Randomized Complete Block Design (RCBD). The volcanic ash dose (V0=0.00; V1=10.00 and V2=20.00 tonnes/Ha) was the second factor, this study with three replications. Parameter were measured plant height, stem diameter, chlorophyll content and yield. The results were showed the PBZ application accelerate of vegetative growth by decreasing plant height, increasing in stem diameter, chlorophyll content and yield as compared to the untreated plant, respectively. Unlike volcanic ash, no significantly in chlorophyll content and stem diameter but significantly different in plant height and yield as compared to control plant, respectively. Therefore, did not founded interaction between volcanic ash with PBZ for all parameters.