Neurons develop dendritic arbors in cell type-specific patterns. Using growing Purkinje cells in culture as a model, we performed a long-term time-lapse observation of dendrite branch dynamics to understand the rules that govern the characteristic space-filling dendrites. We found that dendrite architecture was sculpted by a combination of reproducible dynamic processes, including constant tip elongation, stochastic terminal branching, and retraction triggered by contacts between growing dendrites. Inhibition of protein kinase C/protein kinase D signaling prevented branch retraction and significantly altered the characteristic morphology of long proximal segments. A computer simulation of dendrite branch dynamics using simple parameters from experimental measurements reproduced the time-dependent changes in the dendrite configuration in live Purkinje cells. Furthermore, perturbation analysis to parameters in silico validated the important contribution of dendritic retraction in the formation of the characteristic morphology. We present an approach using live imaging and computer simulations to clarify the fundamental mechanisms of dendrite patterning in the developing brain.