Dendrite morphogenesis is essential for the formation of neural circuitry. As dendritic architectures profoundly affect neuronal functions, establishing cell type-specific dendrite morphologies is critical for diverse functions of neurons. A key question in dendrite morphogenesis is how extracellular cues direct dendritic patterning. In particular, many so-called “space filling” neurons have the capacity to extensively and uniformly cover the receptive field. Whether these neurons are self-sufficient in innervating their target fields or they rely on extracellular permissive signals is unknown. To answer this question, we use Drosophila class IV dendritic arborization (da) neurons as a model system. The dendrites of class IV da neurons completely and non-redundantly cover the larval epidermis. Using RNA interference (RNAi) in epidermal cells, we discovered that the innervation of receptive fields by class IV da neurons require epidermis-derived heparan sulfate proteoglycans (HSPGs), a type of extracellular or membrane-associated glycoproteins. This suggests the existence of an extracellular permissive signal for the dendritic growth of class IV da neurons. Our loss-of-function (LOF) analyses of HSPG genes demonstrated that Syndecan (Sdc) and Dally act redundantly to promote the local growth of high order dendritic branches. By conducting time-lapse imaging, we found that HSPGs are not required for short-term dynamics of terminal dendrites but are necessary for stabilizing dendritic microtubules. Rather than promoting dendritic growth by binding to secreted ligands, our data suggest that HSPGs themselves may serve as the permissive signal. Supporting this hypothesis, we found that receptor protein tyrosine phosphatase Ptp69D, a HSPG receptor expressed in class IV da neurons, is required for the growth of and the microtubule stabilization in class IV da dendrites. Together, our results demonstrate that HSPGs are permissive signals for dendritic growth of space-filling class IV da neurons.