A growing world population drives an ever-increasing need for food and energy. These challenges, along with depletion of water and fossil fuel resources, call for improvements in crop production systems and the cultivars used within them. Perennial cropping systems present an attractive solution to many of these problems. A greater understanding of the genetic control of over-wintering ability within crop species is one way to begin the process of making perennial cropping systems a possibility. In this study an F3:F4 family derived from a cross between Sorghum bicolor (L.) Moench and S. propinquum (Kunth) Hitchc. segregating for rhizome production was phenotyped in both field and greenhouse environments for traits relating to rhizomatousness and over-wintering. Several statistical models were created to correlate rhizome growth and over-wintering. A known rhizome quantitative trait locus (QTL) region was saturated with SSR markers and the QTL interval was reduced from previous estimates of about 16 Mb or 7 cM to 12 Mb or 2 cM, a 25% or 71% reduction in physical or linkage distance respectively. Two previously unidentified QTL regions associated with over-wintering were also identified. Our results also support the hypothesis that rhizome growth is important and possibly necessary for over-wintering in Sorghum.