Ensilage, a traditional forage preservation method for ruminants, has been demonstrated as a promising preservation and pretreatment strategy for bioconversion of lignocellulosic biomass. In temperature climates the corn stover harvest can extend from early fall to early winter, during which the chemical composition of stover varies significantly and influences the silage process. Although the effects of maturity on ensilage has been studied for conventional summer whole-plant corn silage, we are not aware of any prior research on the effects of harvest date on fall harvested corn stover (without the grain). Similarly, little is known about the influence of enzyme addition and water addition on ensilage of mature crop residues at different harvest dates. The aim of this study was to explore the effects of harvest date, water addition, and enzyme addition and their interactions with the characteristics of corn stover silage. Corn stover was harvested weekly between Oct.05 and Nov.29. Replicated 500g samples were subsequently ensiled at 37ºC with and without enzyme treatments at both field moisture and 60% moisture (w.b.). Total mass loss, pH, dry matter, water soluble carbohydrate, cellulose, hemicellulose and monosaccharides were analyzed on days 0,1,7 and 21. Results indicated that earlier fall was the best harvest date.  The moisture content of corn stover, cob and corn were significantly influenced by harvest date, with dry matter loss, cellulose degradation percentage, water soluble carbohydrate and monosaccharides significantly increased by enzyme addition. Identifying the optimum harvest period can help maximize utilization of stover as a feedstock for bioethanol.