We report the controlled self-seeded growth of highly crystalline Ge nanowires, in the absence of conventional metal seed catalysts, using a variety of oligosilylgermane precursors and mixtures of germane and silane compounds (Ge:Si ratios between 1:4 and 1:1). The nanowires produced were encased in an amorphous shell of material derived from the precursors, which acted to isolate the Ge seed particles from which the nanowires were nucleated. The mode diameter and size distribution of the nanowires were found to increase as the growth temperature and Ge content in the precursors increased. Specifically, a model was developed to describe the main stages of self-seeded Ge nanowire growth (nucleation, coalescence, and Ostwald ripening) from the oligosilylgermane precursors and, in conjunction with TEM analysis, a mechanism of growth was proposed.